{
    "mode": "man",
    "parameter": "ksh93",
    "section": "1",
    "url": "https://www.chedong.com/phpMan.php/man/ksh93/1/json",
    "generated": "2026-09-01T12:01:19Z",
    "synopsis": "ksh [ ±abcefhiklmnprstuvxBCDEGH ] [ ±o option ] ... [ - ] [ arg ... ]\nrksh [ ±abcefhiklmnpstuvxBCDEGH ] [ ±o option ] ... [ - ] [ arg ... ]",
    "sections": {
        "NAME": {
            "content": "ksh, rksh - KornShell, a standard/restricted command and programming language\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "ksh [ ±abcefhiklmnprstuvxBCDEGH ] [ ±o option ] ... [ - ] [ arg ... ]\nrksh [ ±abcefhiklmnpstuvxBCDEGH ] [ ±o option ] ... [ - ] [ arg ... ]\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "Ksh  is  a  command and programming language that executes commands read from a terminal or a\nfile.  Rksh is a restricted version of the command interpreter ksh; it is used to set up  lo‐\ngin names and execution environments whose capabilities are more controlled than those of the\nstandard shell.  See Invocation below for the meaning of arguments to the shell.\n",
            "subsections": [
                {
                    "name": "Definitions.",
                    "content": "A metacharacter is one of the following characters:\n\n;   &   (   )   |   <   >   new-line   space   tab\n\nA  blank is a tab or a space.  An identifier is a sequence of letters, digits, or underscores\nstarting with a letter or underscore.  Identifiers are used as components of variable  names.\nA  vname is a sequence of one or more identifiers separated by a . and optionally preceded by\na ..  Vnames are used as function and variable names.  A word is  a  sequence  of  characters\nfrom the character set defined by the current locale, excluding non-quoted metacharacters.\n\nA  command  is a sequence of characters in the syntax of the shell language.  The shell reads\neach command and carries out the desired action either directly or by invoking separate util‐\nities.  A built-in command is a command that is carried out by the shell itself without  cre‐\nating a separate process.  Some commands are built in purely for convenience and are not doc‐\numented  here.  Built-ins that cause side effects in the shell environment and built-ins that\nare found before performing a path search (see Execution below)  are  documented  here.   For\nhistorical  reasons,  some of these built-ins behave differently than other built-ins and are\ncalled special built-ins.\n"
                },
                {
                    "name": "Commands.",
                    "content": "A simple-command is a list of variable assignments (see Variable Assignments below) or a  se‐\nquence  of blank separated words which may be preceded by a list of variable assignments (see\nEnvironment below).  The first word specifies the name of the command to be executed.  Except\nas specified below, the remaining words are passed as arguments to the invoked command.   The\ncommand  name  is  passed  as argument 0 (see exec(2)).  The value of a simple-command is its\nexit status; 0-255 if it terminates normally; 256+signum if  it  terminates  abnormally  (the\nname  of the signal corresponding to the exit status can be obtained via the -l option of the\nkill built-in utility).\n\nA pipeline is a sequence of one or more commands separated by |.  The standard output of each\ncommand but the last is connected by a socketpair(2) or (if the posix shell option is on)  by\na  pipe(2)  to  the  standard input of the next command.  Each command except the last is run\nasynchronously in a subshell (see Subshells below).  If the monitor or pipefail option is on,\nor the pipeline is preceded by the reserved word time, then the shell waits for all component\ncommands in the pipeline to terminate; otherwise, the shell only waits for the last component\ncommand.  The exit status of a pipeline is the exit status of its last component command, un‐\nless the pipefail option is enabled.  Each pipeline can be preceded by the  reserved  word  !\nwhich  causes the exit status of the pipeline to become 0 if the exit status of the last com‐\nmand is non-zero, and 1 if the exit status of the last command is 0.\n\nA list is a sequence of one or more pipelines separated by ;, &, |&, &&, or ||,  and  option‐\nally  terminated  by ;, &, or |&.  Of these five symbols, ;, &, and |& have equal precedence,\nwhich is lower than that of && and ||.  The symbols && and || also have equal precedence.   A\nsemicolon  (;) causes sequential execution of the preceding pipeline; an ampersand (&) causes\nasynchronous execution of the preceding pipeline (i.e., the shell  does  not  wait  for  that\npipeline  to  finish).  The symbol |& causes asynchronous execution of the preceding pipeline\nwith a two-way pipe established to the parent shell; the standard input  and  output  of  the\nspawned pipeline can be written to and read from by the parent shell by applying the redirec‐\ntion  operators  <& and >& with arg p to commands and by using -p option of the built-in com‐\nmands read and print described later.  The symbol && (||) causes the list following it to  be\nexecuted  only  if  the preceding pipeline returns a zero (non-zero) value.  One or more new-\nlines may appear in a list instead of a semicolon, to delimit a command.  The first item   of\nthe  first  pipeline of a list that is a simple command not beginning with a redirection, and\nnot occurring within a while, until, or if list, can be preceded by a semicolon.  This  semi‐\ncolon  is  ignored unless the showme option is enabled as described with the set built-in be‐\nlow.\n\nA command is either a simple-command or a compound-command, which is one  of  the  following.\nUnless  otherwise  stated, the value returned by a command is that of the last simple-command\nexecuted in the command.\n\nfor vname [ in word ... ] ;do list ;done\nEach time a for command is executed, vname is set to the next word taken from  the  in\nword list.  If in word ...  is omitted, then the for command executes the do list once\nfor each positional parameter that is set starting from 1 (see Parameter Expansion be‐\nlow).  Execution ends when there are no more words in the list.\n\nfor (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done\nThe  arithmetic expression expr1 is evaluated first (see Arithmetic Evaluation below).\nThe arithmetic expression expr2 is repeatedly evaluated until it evaluates to zero and\nwhen non-zero, list is executed and the arithmetic expression expr3 evaluated.  If any\nexpression is omitted, then it behaves as if it evaluated to 1.\n\nselect vname [ in word ... ] ;do list ;done\nA select command prints on standard error (file descriptor 2) the set of  words,  each\npreceded  by  a  number.   If  in word ...  is omitted, then the positional parameters\nstarting from 1 are used instead (see Parameter Expansion below).  The PS3  prompt  is\nprinted and a line is read from the standard input.  If this line consists of the num‐\nber  of  one  of  the listed words, then the value of the variable vname is set to the\nword corresponding to this number.  If this line  is  empty,  the  selection  list  is\nprinted  again.  Otherwise the value of the variable vname is set to the empty string.\nThe contents of the line read from standard input is saved in the variable REPLY.  The\nlist is executed for each selection until a break or end-of-file is  encountered.   If\nthe  REPLY  variable is set to the empty string by the execution of list, then the se‐\nlection list is printed before displaying the PS3 prompt for the next selection.\n\ncase word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac\nA case command executes the list associated with the first pattern that matches  word.\nThe form of the patterns is the same as that used for pathname expansion (see Pathname\nExpansion  below).   The  ;; operator causes execution of case to terminate.  If ;& is\nused in place of ;; the next subsequent list, if any,  is executed.\n\nif list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi\nThe list following if is executed and, if it returns a zero exit status, the list fol‐\nlowing the first then is executed.  Otherwise, the list  following  elif  is  executed\nand, if its value is zero, the list following the next then is executed.  Failing each\nsuccessive  elif  list,  the  else list is executed.  If the if list has non-zero exit\nstatus and there is no else list, then the if command returns a zero exit status.\n\nwhile list ;do list ;done\nuntil list ;do list ;done\nA while command repeatedly executes the while list and, if the exit status of the last\ncommand in the list is zero, executes the do list; otherwise the loop terminates.   If\nno  commands  in  the do list are executed, then the while command returns a zero exit\nstatus; until may be used in place of while to negate the loop termination test.\n\nwhile inputredirection ;do list ;done\nFilescan loop. This is defined by a lone input redirection following  while  (see  In‐\nput/Output  below).   It  is  faster than using the read built-in command in a regular\nwhile loop.  The shell reads lines from the file or stream opened by  inputredirection\nuntil  the end is reached or the loop is broken.  For each line read, the command list\nis executed with the line's contents assigned to the REPLY  variable  and  the  line's\nfields  split into the positional parameters (see Field Splitting and Positional Para‐\nmeters below).  Within the list, standard input is redirected to  /dev/null.   If  the\nposix  compatibility  shell option is on, this loop type is disabled and inputredirec‐\ntion is processed like a lone redirection in any other context.\n\n((expression))\nThe expression is evaluated using the rules for arithmetic evaluation described below.\nIf the value of the arithmetic expression is non-zero, the exit status is 0, otherwise\nthe exit status is 1.\n\n(list)\nExecute list in a subshell (see Subshells below).  Note, that  if  two  adjacent  open\nparentheses are needed for nesting, a space must be inserted to avoid evaluation as an\narithmetic command as described above.\n\n{ list;}\nlist is simply executed.  Note that unlike the metacharacters ( and ), { and } are re‐\nserved  words  and  must  occur at the beginning of a line or after a ; in order to be\nrecognized.\n\n[[ expression ]]\nEvaluates expression and returns a zero exit status when expression is true.  See Con‐\nditional Expressions below, for a description of expression.\n\nfunction varname { list ;} [ redirection ... ]\nvarname () compound-command [ redirection ... ]\nDefine a function which is referenced by varname.  A function whose varname contains a\n.  is called a discipline function and the portion of the varname preceding the last .\nmust refer to an existing variable.  The body of the function is the list of  commands\nbetween { and }.  A function defined with the function varname syntax can also be used\nas an argument to the .  special built-in command to get the equivalent behavior as if\nthe varname() syntax were used to define it.  (See Functions below.)\n\nnamespace identifier { list ;}\nDefines  or  uses the name space identifier and runs the commands in list in this name\nspace.  (See Name Spaces below.)\n\ntime [ pipeline ]\nIf pipeline is omitted the user and system time for the current  shell  and  completed\nchild processes is printed on standard error.  Otherwise, pipeline is executed and the\nelapsed  time  as well as the user and system time are printed on standard error.  The\nTIMEFORMAT variable may be set to a format string that specifies how the timing infor‐\nmation should be displayed.  See Shell Variables below for a description of the  TIME‐\nFORMAT variable.\n\nThe  following reserved words are recognized as reserved only when they are the first word of\na command and are not quoted:\n"
                },
                {
                    "name": "if then else elif fi case esac for while until do done { } function select time [[ ]] !",
                    "content": ""
                },
                {
                    "name": "Variable Assignments.",
                    "content": "One or more variable assignments can start a simple command or can be arguments to the  type‐\nset, enum, export, or readonly special built-in commands as well as to other declaration com‐\nmands created as types.  The syntax for an assignment is of the form:\n\nvarname=word\nvarname[word]=word\nNo space is permitted between varname and the = or between = and word.\n\nvarname=(assignlist)\nNo space is permitted between varname and the =.  The variable varname is unset before\nthe assignment.  An assignlist can be one of the following:\nword ...\nIndexed array assignment.\n[word]=word ...\nAssociative array assignment.  If preceded by typeset -a this will cre‐\nate an indexed array instead.\nassignment ...\nCompound variable assignment.  This creates a compound variable varname\nwith subvariables of the form varname.name, where name is the name por‐\ntion  of assignment.  The value of varname will contain all the assign‐\nment elements.  Additional assignments made to subvariables of  varname\nwill  also be displayed as part of the value of varname.  If no assign‐\nments are specified, varname will be a compound variable allowing  sub‐\nsequence child elements to be defined.\ntypeset [options] assignment ...\nNested  variable  assignment.  Multiple assignments can be specified by\nseparating each of them with a ;.  The previous value is  unset  before\nthe assignment.  Other declaration commands such as readonly, enum, and\nother declaration commands can be used in place of typeset.\n. filename\nInclude the assignment commands contained in filename.\n\nIn addition, a += can be used in place of the = to signify adding to or appending to the pre‐\nvious  value.   When  += is applied to an arithmetic type, word is evaluated as an arithmetic\nexpression and added to the current value.  When applied to a string variable, the value  de‐\nfined  by word is appended to the value.  For compound assignments, the previous value is not\nunset and the new values are appended to the current ones provided that the types are compat‐\nible.\n\nThe right hand side of a variable assignment undergoes all the expansion listed below  except\nword  splitting,  brace expansion, and pathname expansion.  When the left hand side is an as‐\nsignment is a compound variable and the right hand is the name of a  compound  variable,  the\ncompound  variable  on  the  right will be copied or appended to the compound variable on the\nleft.\n"
                },
                {
                    "name": "Comments.",
                    "content": "A word beginning with # causes that word and all the following characters up to a new-line to\nbe ignored.\n"
                },
                {
                    "name": "Aliasing.",
                    "content": "The first word of each command is replaced by the text of an alias if an alias for this  word\nhas  been  defined.  An alias name consists of any number of characters excluding metacharac‐\nters, quoting characters, file expansion characters, parameter expansion and command  substi‐\ntution  characters,  the  characters  /  and =.  The replacement string can contain any valid\nshell script including the metacharacters listed above.  The first word of  each  command  in\nthe  replaced  text, other than any that are in the process of being replaced, will be tested\nfor aliases.  If the last character of the alias value is a blank then the word following the\nalias will also be checked for alias substitution.  Aliases can be used to redefine  built-in\ncommands but cannot be used to redefine the reserved words listed above.  Aliases can be cre‐\nated and listed with the alias command and can be removed with the unalias command.\n\nAliasing  is performed when scripts are read, not while they are executed.  Therefore, for an\nalias to take effect, the alias definition command has to  be  executed  before  the  command\nwhich references the alias is read.\n\nThe  following  aliases  are automatically preset when the shell is invoked as an interactive\nshell.  Preset aliases can be unset or redefined.\nhistory=′hist -l′\nr=′hist -s′\n"
                },
                {
                    "name": "Tilde Expansion.",
                    "content": "After alias substitution is performed, each word is checked to see if it begins with  an  un‐\nquoted  ∼.   For tilde expansion, word also refers to the word portion of parameter expansion\n(see Parameter Expansion below).  If a word is preceded by a tilde, then it is checked up  to\na / to see if it matches a user name in the password database (see getpwname(3)).  If a match\nis found, the ∼ and the matched login name are replaced by the login directory of the matched\nuser.  If no match is found, the original text is left unchanged.  A ∼ by itself, or in front\nof  a  /,  is replaced by $HOME, unless the HOME variable is unset, in which case the current\nuser's home directory as configured in the operating system is used.  A ∼ followed by a +  or\n- is replaced by $PWD or $OLDPWD respectively.\n\nIn addition, when expanding a variable assignment (see Variable Assignments above), tilde ex‐\npansion  is  attempted when the value of the assignment begins with a ∼, and when a ∼ appears\nafter a :.  A : also terminates a user name following a ∼.\n\nThe tilde expansion mechanism may be extended or modified by defining one of  the  discipline\nfunctions  .sh.tilde.set or .sh.tilde.get (see Functions and Discipline Functions below).  If\neither exists, then upon encountering a tilde word to expand, that function  is  called  with\nthe  tilde  word  assigned  to either .sh.value (for the .sh.tilde.set function) or .sh.tilde\n(for the .sh.tilde.get function).  Performing tilde expansion within  a  discipline  function\nwill  not recursively call that function, but default tilde expansion remains active, so lit‐\neral tildes should still be quoted where required.  Either function may assign a  replacement\nstring to .sh.value.  If this value is non-empty and does not start with a ∼, it replaces the\ndefault tilde expansion when the function terminates.  Otherwise, the tilde expansion is left\nunchanged.\n"
                },
                {
                    "name": "Subshells.",
                    "content": "A  subshell  is  a separate execution environment that is a complete duplicate of the current\nshell environment, except for two things: all traps are reset to  default  except  those  for\nsignals  that are being ignored, and subshells cannot be interactive (i.e., they have no com‐\nmand prompt).  Changes made within a subshell do not affect the parent  environment  and  are\nlost when the subshell exits.\n\nParticular  care should be taken not to confuse a subshell with a newly invoked shell that is\nmerely a child process of the current shell,  and  which  (unlike  a  subshell)  starts  from\nscratch  in terms of variables and functions and may be interactive.  Beware of shell tutori‐\nals on the Internet that confuse these.\n\nSubshells cannot be created or invoked using any command.  Instead, the following  are  auto‐\nmatically run in a subshell:\n\n•  any command or group of commands enclosed in parentheses;\n\n•  command  substitutions  of  the first and third form (see Command Substitution be‐\nlow);\n\n•  process substitutions (see Process Substitution below);\n\n•  all elements of a pipeline except the last;\n\n•  any command executed asynchronously (i.e., in a background process).\n\nCreating processes is expensive, so as a performance optimization, a subshell of a non-inter‐\nactive shell may share the process of its parent environment. Such a subshell is known  as  a\nvirtual subshell.  Subshells are virtual unless or until something (such as asynchronous exe‐\ncution,  or an attempt to set a process limit using the ulimit built-in command, or other im‐\nplementation- or system-defined requirements) makes it necessary to fork(2) it into  a  sepa‐\nrate  process.   Barring any bugs in the shell, virtual subshells should be indistinguishable\nfrom real subshells except by their execution speed and their process ID.  See  the  descrip‐\ntion of the .sh.pid variable below for more information.\n"
                },
                {
                    "name": "Command Substitution.",
                    "content": "The  standard  output from a command list enclosed in parentheses preceded by a dollar sign (\n$(list) ), or in a brace group preceded by a dollar sign ( ${ list;} ), or in a pair of grave\naccents (``) may be used as part or all of a word; trailing new-lines are  removed.   In  the\nsecond  case,  the  {  and  } are treated as a reserved words so that { must be followed by a\nblank and } must appear at the beginning of the line or follow a ;.  In the third  (obsolete)\nform,  the  string  between the quotes is processed for special quoting characters before the\ncommand is executed (see Quoting below).  The command substitution $(cat  file)  can  be  re‐\nplaced by the equivalent but faster $(<file).  The command substitution $(n<#) will expand to\nthe  current byte offset for file descriptor n.  Except for the second form, the command list\nis run in a subshell so that no side effects are possible.  For the second form, the final  }\nwill be recognized as a reserved word after any token.\n"
                },
                {
                    "name": "Arithmetic Expansion.",
                    "content": "An  arithmetic  expression enclosed in double parentheses preceded by a dollar sign ( $(()) )\nis replaced by the value of the arithmetic expression within the double parentheses.\n"
                },
                {
                    "name": "Process Substitution.",
                    "content": "Each command argument of the form <(list) or >(list) will  run  process  list  asynchronously\nconnected to some file in /dev/fd if this directory exists, or else a fifo in a temporary di‐\nrectory.   The name of this file will become the argument to the command.  If the form with >\nis selected then writing on this file will provide input for list.  If < is  used,  then  the\nfile passed as an argument will contain the output of the list process.  For example,\n\npaste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)\n\ncuts fields 1 and 3 from the files file1 and file2 respectively, pastes the results together,\nand  sends it to the processes process1 and process2, as well as putting it onto the standard\noutput.  Note that the file, which is passed as an argument to the command, is a UNIX pipe(2)\nso programs that expect to lseek(2) on the file will not work.\n\nProcess substitution of the form <(list) can also be used with  the  <  redirection  operator\nwhich  causes the output of list to be standard input or the input for whatever file descrip‐\ntor is specified.\n"
                },
                {
                    "name": "Parameter Expansion.",
                    "content": "A parameter is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and\n!.  A variable is denoted by a vname.  To create a variable whose vname contains a ., a vari‐\nable whose vname consists of everything before the last . must already exist.  A variable has\na value and zero or more attributes.  Variables can be assigned values and attributes by  us‐\ning  the  typeset  special  built-in  command.  The attributes supported by the shell are de‐\nscribed later with the typeset special built-in command.  Exported variables pass  their  at‐\ntributes  to the environment so that a newly invoked ksh that is a child or exec'd process of\nthe current shell will automatically import them, unless the posix shell option is on.\n\nThe shell supports both indexed and associative arrays.  An element of an array  variable  is\nreferenced  by a subscript.  A subscript for an indexed array is denoted by an arithmetic ex‐\npression (see Arithmetic Evaluation below) between a [ and a ].  To assign values to  an  in‐\ndexed  array,  use vname=(value ...) or set -A vname  value ... .  The value of all non-nega‐\ntive subscripts must be in the range of 0 through 4,194,303.  A negative subscript is treated\nas an offset from the maximum current index +1 so that -1 refers to the  last  element.   In‐\ndexed  arrays  can be declared with the -a option to typeset.  Indexed arrays need not be de‐\nclared.  Any reference to a variable with a valid subscript is legal and  an  array  will  be\ncreated if necessary.\n\nAn  associative  array is created with the -A option to typeset.  A subscript for an associa‐\ntive array is denoted by a string enclosed between [ and ].\n\nReferencing any array without a subscript is equivalent to referencing the  array  with  sub‐\nscript 0.\n\nThe value of a variable may be assigned by writing:\n\nvname=value [ vname=value ] ...\n\nor\n\nvname[subscript]=value [ vname[subscript]=value ] ...\n\nNote that no space is allowed before or after the =.\n\nAttributes  assigned by the typeset special built-in command apply to all elements of the ar‐\nray.  An array element can be a simple variable, a compound variable or  an  array  variable.\nAn  element  of  an indexed array can be either an indexed array or an associative array.  An\nelement of an associative array can also be either.  To refer to an  array  element  that  is\npart  of  an  array element, concatenate the subscript in brackets.  For example, to refer to\nthe foobar element of an associative array that is defined as the third element  of  the  in‐\ndexed array, use ${vname[3][foobar]}\n\nA  nameref  is a variable that is a reference to another variable.  A nameref is created with\nthe -n attribute of typeset or with the equivalent nameref command.  The value of  the  vari‐\nable  at  the  time of that command becomes the variable that will be referenced whenever the\nnameref variable is used.  The name of a nameref cannot contain a  ..   When  a  variable  or\nfunction name contains a ., and the portion of the name up to the first . matches the name of\na  nameref,  the  variable  referred to is obtained by replacing the nameref portion with the\nname of the variable referenced by the nameref.  If a nameref is used as the index of  a  for\nloop, a name reference is established for each item in the list.\n\nA  nameref provides a convenient way to refer to the variable inside a function whose name is\npassed as an argument to a function.  For example, if the name of a variable is passed as the\nfirst argument to a function, the command typeset -n var=$1 (a.k.a.  nameref  var=$1)  inside\nthe function causes references and assignments to var to be references and assignments to the\nvariable  whose name has been passed to the function.  Note that, for this to work, the posi‐\ntional parameter must be assigned directly to the nameref as part of the declaration command,\nas in the example above; only that idiom can allow one function to access a local variable of\nanother.  For instance, typeset -n var; var=$1 won't cross that  barrier,  nor  will  typeset\nfoo=$1; typeset -n var=foo.\n\nIf  any of the floating point attributes, -E, -F, or -X, or the integer attribute, -i, is set\nfor vname, then the value is subject to arithmetic evaluation as described below.\n\nPositional parameters, parameters denoted by a number, may be assigned values  with  the  set\nspecial built-in command.  Parameter $0 is set from argument zero when the shell is invoked.\n\nThe character $ is used to introduce substitutable parameters.\n\n${parameter}\nThe  shell reads all the characters from ${ to the matching } as part of the same word\neven if it contains braces or metacharacters.  The value, if any, of the parameter  is\nsubstituted.   The  braces are required when parameter is followed by a letter, digit,\nor underscore that is not to be interpreted as part of its  name,  when  the  variable\nname contains a ..  The braces are also required when a variable is subscripted unless\nit  is  part of an Arithmetic Expression or a Conditional Expression.  If parameter is\none or more digits then it is a positional parameter.  A positional parameter of  more\nthan one digit must be enclosed in braces.  If parameter is * or @, then all the posi‐\ntional  parameters,  starting with $1, are substituted (separated by a field separator\ncharacter).  If an array vname with last subscript * @, or for indexed arrays  of  the\nform sub1 ..  sub2.  is used, then the value for each of the elements between sub1 and\nsub2  inclusive  (or  all elements for * and @) is substituted, separated by the first\ncharacter of the value of IFS.\n\n${#parameter}\nIf parameter is * or @, the number of positional parameters  is  substituted.   Other‐\nwise, the length of the value of the parameter is substituted.\n\n${#vname[*]}\n${#vname[@]}\nThe number of elements in the array vname is substituted.\n\n${@vname}\nExpands to the type name (See Type Variables  below) or attributes of the variable re‐\nferred to by vname.\n\n${!vname}\nExpands  to  the name of the variable referred to by vname.  This will be vname except\nwhen vname is a name reference.\n\n${!vname[subscript]}\nExpands to name of the subscript unless subscript is *, @.  or of  the  form  sub1  ..\nsub2.   When subscript is *, the list of array subscripts for vname is generated.  For\na variable that is not an array, the value is 0 if the variable is set.  Otherwise  it\nis  the  empty  string.   When subscript is @, same as above, except that when used in\ndouble quotes, each array subscript yields a separate argument.  When subscript is  of\nthe  form sub1 ..  sub2 it expands to the list of subscripts between sub1 and sub2 in‐\nclusive using the same quoting rules as @.\n\n${!prefix@}\n${!prefix*}\nThese both expand to the names of the variables whose names begin  with  prefix.   The\nexpansions otherwise work like $@ and $*, respectively (see under Quoting below).\n\n${parameter:-word}\nIf  parameter  is  set and has a non-empty value, then substitute its value; otherwise\nsubstitute word.\n\n${parameter:=word}\nIf parameter is not set or has the empty string value, then set it to word; the  value\nof the parameter is then substituted.  Positional parameters may not be assigned to in\nthis way.\n\n${parameter:?word}\nIf  parameter  is set and has a non-empty value, then substitute its value; otherwise,\nprint word and exit from the shell (if not interactive).  If word is  omitted  then  a\nstandard message is printed.\n\n${parameter:+word}\nIf  parameter is set and has a non-empty value then substitute word; otherwise substi‐\ntute the empty string.\n\nIn the above, word is not evaluated unless it is to be used as  the  substituted  string,  so\nthat,  in the following example, pwd is executed only if d is not set or has the empty string\nvalue:\n\nprint ${d:-$(pwd)}\n\nIf the colon (:) is omitted from the above expressions, then the shell  only  checks  whether\nparameter is set or not.\n\n${parameter:offset:length}\n${parameter:offset}\nExpands  to  the portion of the value of parameter starting at the character (counting\nfrom 0) determined by expanding offset as an arithmetic expression and  consisting  of\nthe  number  of  characters determined by the arithmetic expression defined by length.\nIn the second form, the remainder of the value is used.  If A negative  offset  counts\nbackwards  from  the  end  of  parameter.  Note that one or more blanks is required in\nfront of a minus sign to prevent the shell from interpreting the operator as  :-.   If\nparameter is * or @, or is an array name indexed by * or @, then offset and length re‐\nfer  to  the  array  index  and number of elements respectively.  A negative offset is\ntaken relative to one greater than the highest subscript for indexed arrays.  The  or‐\nder for associative arrays is unspecified.\n\n${parameter#pattern}\n${parameter##pattern}\nIf  the  shell pattern matches the beginning of the value of parameter, then the value\nof this expansion is the value of the parameter with the matched portion deleted; oth‐\nerwise the value of this parameter is substituted.  In the  first  form  the  smallest\nmatching  pattern  is  deleted  and in the second form the largest matching pattern is\ndeleted.  When parameter is @, *, or an array variable with subscript @ or *, the sub‐\nstring operation is applied to each element in turn.\n\n${parameter%pattern}\n${parameter%%pattern}\nIf the shell pattern matches the end of the value of parameter, then the value of this\nexpansion is the value of the parameter with the matched part deleted; otherwise  sub‐\nstitute  the  value  of parameter.  In the first form the smallest matching pattern is\ndeleted and in the second form the largest matching pattern is deleted.  When  parame‐\nter  is  @,  *, or an array variable with subscript @ or *, the substring operation is\napplied to each element in turn.\n\n${parameter/pattern/string}\n${parameter//pattern/string}\n${parameter/#pattern/string}\n${parameter/%pattern/string}\nExpands parameter and replaces the longest match of pattern  with  the  given  string.\nEach  occurrence  of \\n in string is replaced by the portion of parameter that matches\nthe n-th subpattern.  In the first form, only the first occurrence of pattern  is  re‐\nplaced.   In  the second form, each match for pattern is replaced by the given string.\nThe third form restricts the pattern match to the beginning of the  string  while  the\nfourth  form  restricts  the pattern match to the end of the string.  In the first and\nsecond forms, an empty pattern never matches.  In the third and fourth forms, an empty\npattern matches the beginning or the end of the string, respectively.  When string  is\nempty,  the pattern will be deleted and the / in front of string may be omitted.  When\nparameter is @, *, or an array variable with subscript @ or *, the substitution opera‐\ntion is applied to each element in turn.  In this case, the  string  portion  of  word\nwill be re-evaluated for each element.\n"
                },
                {
                    "name": "Shell Variables.",
                    "content": "The following parameters are automatically set by the shell:\n#      The number of positional parameters in decimal.\n\n-      Options supplied to the shell on invocation or by the set command.\n\n?      The  exit  status returned by the last executed command. Its meaning depends on\nthe command or function that defines it, but there are conventions  that  other\ncommands  often  depend on: zero typically means 'success' or 'true', one typi‐\ncally means 'non-success' or 'false', and a value greater  than  one  typically\nindicates some kind of error. Only the 8 least significant bits of $? (values 0\nto  255)  are  preserved when the exit status is passed on to a parent process,\nbut within the same (sub)shell environment, it is a signed integer value with a\nrange of possible values as shown by the commands getconf INTMIN  and  getconf\nINTMAX.  Shell functions that run in the current environment may return status\nvalues in this range.\n\n$      The process ID of the main shell process. Note that this value will not  change\nin  a  subshell,  even  if  the subshell runs in a different process.  See also\n.sh.pid.\n\nInitially, the value of  is an absolute pathname of the shell or script  being\nexecuted  as  passed  in the environment.  Subsequently it is assigned the last\nargument of the previous command.  This parameter is not set for commands which\nare asynchronous.  This parameter is also used to hold the name of the matching\nMAIL file when checking for mail.  While defining  a  compound  variable  or  a\ntype,  is initialized as a reference to the compound variable or type.  When a\ndiscipline function is invoked,  is initialized as a reference to the variable\nassociated  with the call to this function.  Finally when  is used as the name\nof the first variable of a type definition, the new type is  derived  from  the\ntype of the first variable. (See Type Variables  below.)\n\n!      The  process  ID  of the last background command invoked or the most recent job\nput in the background with the bg built-in command.\n\n.sh.command\nWhen processing a DEBUG trap, this variable contains the current  command  line\nthat  is about to run.  The value is in the same format as the output generated\nby the xtrace option (minus the preceding PS4 prompt).\n\n.sh.edchar\nThis variable contains the value of the  keyboard  character  (or  sequence  of\ncharacters  if  the first character is an ESC, ASCII 033) that has been entered\nwhen processing a KEYBD trap (see Key Bindings below).  If the value is changed\nas part of the trap action, then the new value replaces the  key  (or  key  se‐\nquence) that caused the trap.\n\n.sh.edcol\nThe character position of the cursor at the time of the most recent KEYBD trap.\n\n.sh.edmode\nUpon  executing  a  KEYBD trap action, the value of this variable is set to the\nESC control character if the shell is in vi input mode (See Vi  Editing  Mode\nbelow), or to the empty string value otherwise.\n\n.sh.edtext\nThe  characters  in the input buffer at the time of the most recent KEYBD trap.\nThe variable is unset when not processing a KEYBD trap.\n\n.sh.file\nThe pathname of the file that contains the current command.\n\n.sh.fun\nThe name of the current function that is being executed.\n\n.sh.level\nSet to the current call depth of functions and  dot  scripts.   Normally,  this\nvariable  is  read-only,  but  while  executing  a DEBUG trap, its value may be\nchanged to switch the current function scope to that of the specified level for\nthe duration of the trap run, making it possible to access a parent  scope  for\ndebugging  purposes.   When trap execution ends, the variable and the scope are\nrestored.  It is an error to assign a value lower than 0 (the global scope)  or\nhigher than the current call depth.\n\n.sh.lineno\nSet during a DEBUG trap to the line number for the caller of each function.\n\n.sh.match\nWhenever  a  match is found in a pattern matching operation using either the [[\ncompound command (see Conditional Expressions below) or the expansions  ${para‐\nmeter#pattern},  ${parameter%pattern},  ${parameter/pattern/string},  or one of\ntheir variants (see Parameter Expansion above), the match  and  its  subpattern\nmatches are stored in this indexed array, overwriting its previous values.  The\n0-th  element  stores  the  complete match and the i-th element stores the i-th\nsubmatch.  For //, the array is two-dimensional, with the first subscript indi‐\ncating the most recent match and subpattern match, and the second subscript in‐\ndicating which match with 0 representing the  first  match.   If  no  match  is\nfound,  .sh.match is not reset or modified.  Note that even matching operations\nperformed on the .sh.match variable itself will overwrite  it  upon  finding  a\nmatch.\n\n.sh.math\nUsed  for  defining  arithmetic functions (see Arithmetic Evaluation below) and\nstores the list of user defined arithmetic functions.\n\n.sh.name\nSet to the name of the variable at the time that a discipline function  is  in‐\nvoked.\n\n.sh.subscript\nSet  to  the name subscript of the variable at the time that a discipline func‐\ntion is invoked.\n\n.sh.subshell\nThe current depth for subshells and command substitution.\n\n.sh.pid\nSet to the process ID of the current shell process.  Unlike $$, this is updated\nin a subshell when it forks into a new process.  Note that a  virtual  subshell\nmay have to fork mid-execution due to various system- and implementation-depen‐\ndent  requirements,  so  the  value should not be counted on to remain the same\nfrom one command to the next.  If a persistent process ID  is  required  for  a\nsubshell,  it  must be ensured it is running in its own process first.  Any at‐\ntempt to set a process limit using the ulimit built-in command, such as  ulimit\n-t  unlimited  2>/dev/null,  is  a  reliable  way to make a subshell fork if it\nhasn't already.\n\n.sh.ppid\nSet to the process ID of the parent  of  the  current  shell  process.   Unlike\n$PPID,  this  is  updated  in a subshell when it forks into a new process.  The\nsame note as for .sh.pid applies.\n\n.sh.value\nSet to the value of the variable at the time that the set or append  discipline\nfunction  is  invoked.  When a user defined arithmetic function is invoked, the\nvalue of .sh.value is saved and .sh.value  is  set  to  long  double  precision\nfloating point.  .sh.value is restored when the function returns.\n\n.sh.version\nSet to a value that identifies the version of this shell.\n\nCOLUMNS\nWidth  of the terminal window in character positions.  Updated automatically at\ninitialization and on receiving a SIGWINCH signal.  The shell uses the value to\ndefine the width of the edit window for the shell edit modes and  for  printing\nselect lists.\n\nKSHVERSION\nA name reference to .sh.version.\n\nLINENO The current line number within the script or function being executed.\n\nLINES  Height  of  the terminal window in lines.  Updated automatically at initializa‐\ntion and on receiving a SIGWINCH signal.  The shell uses the value to determine\nthe column length for printing select lists: they are printed vertically  until\nabout two thirds of LINES lines are filled.\n\nOLDPWD The previous working directory set by the cd command.\n\nOPTARG The  value  of  the last option argument processed by the getopts built-in com‐\nmand.\n\nOPTIND The index of the last option argument processed by the  getopts  built-in  com‐\nmand.\n\nPPID   The  process  ID of the parent of the main shell process.  Note that this value\nwill not change in a subshell,  even  if  the  subshell  runs  in  a  different\nprocess.  See also .sh.ppid.\n\nPWD    The present working directory set by the cd command.\n\nRANDOM Each  time this variable is referenced, a random integer, uniformly distributed\nbetween 0 and 32767, is generated.  The sequence of random numbers can be  ini‐\ntialized by assigning a numeric value to RANDOM.\n\nREPLY  This  variable  is set by the select statement and by the read built-in command\nwhen no arguments are supplied.\n\nSECONDS\nEach time this variable is referenced, the number of seconds since shell  invo‐\ncation  is  returned.  If this variable is assigned a value, then the value re‐\nturned upon reference will be the value that was assigned plus  the  number  of\nseconds since the assignment.\n\nSHLVL  An integer variable that is incremented and exported each time the shell is in‐\nvoked.  If SHLVL is not in the environment when the shell is invoked, it is set\nto 1.\n\nThe following variables are used by the shell:\nCDPATH The search path for the cd command.\n\nEDITOR If  the  VISUAL variable is not set, the value of this variable will be checked\nfor certain patterns and the corresponding editing option will be turned on  as\ndescribed with VISUAL below.\n\nENV    If  this  variable  is set, then parameter expansion, command substitution, and\narithmetic expansion are performed on the value to generate the pathname of the\nscript that will be executed when the shell is invoked interactively (see Invo‐\ncation below).  This file is typically used for alias and function definitions.\nThe default value is $HOME/.kshrc.  On  systems  that  support  a  system  wide\n/etc/ksh.kshrc  initialization file, if the filename generated by the expansion\nof ENV begins with /./ or ././ the system wide initialization file will not  be\nexecuted.\n\nFCEDIT Obsolete  name for the default editor name for the hist command.  FCEDIT is not\nused when HISTEDIT is set.\n\nFIGNORE\nA pattern that defines the set of filenames that will be ignored when  perform‐\ning filename matching.\n\nFPATH  The  search  path  for  function definitions.  The directories in this path are\nsearched for a file with the same name as the function or command when a  func‐\ntion  with  the -u attribute is referenced and when a command is not found.  If\nan executable file with the name of that command is found, then it is read  and\nexecuted  in  the current environment.  Unlike PATH, the current directory must\nbe represented explicitly by .  rather than by adjacent : characters or  a  be‐\nginning or ending :.\n\nhistchars\nThis  variable can be used to specify up to three ASCII characters that control\nhistory expansion (see History Expansion below).  The first (default:  !)  sig‐\nnals  the  start  of  a history expansion.  The second (default: ^) is used for\nshort-form substitutions.  The third (default: #),  when  found  as  the  first\ncharacter of a word, causes history expansion to be skipped for the rest of the\nwords  on  the  line.  Multi-byte characters (e.g. UTF-8) are not supported and\nproduce undefined results.\n\nHISTCMD\nNumber of the current command in the history file.\n\nHISTEDIT\nName for the default editor name for the hist command.\n\nHISTFILE\nIf this variable is set when the shell is invoked, then the value is the  path‐\nname  of  the  file that will be used to store the command history (see Command\nRe-entry below).\n\nHISTSIZE\nIf this variable is set when the shell is invoked, then the  number  of  previ‐\nously  entered  commands that are accessible by this shell will be greater than\nor equal to this number.  The default is 512.\n\nHOME   The default argument (home directory) for the cd command.\n\nIFS    Internal field separators, normally space, tab, and new-line that are  used  to\nseparate the results of command substitution or parameter expansion and to sep‐\narate  fields  with  the built-in command read.  The first character of the IFS\nvariable is used to separate arguments for the \"$*\" expansion (see Quoting  be‐\nlow).   Each  single  occurrence  of an IFS character in the string to be split\nthat is not in the isspace character class, and any adjacent characters in  IFS\nthat  are in the isspace character class, delimit a field.  One or more charac‐\nters in IFS that belong to the isspace character class delimit a field.  In ad‐\ndition, if the same isspace character appears consecutively inside IFS and  the\nposix  shell  option  is not on, this character is treated as if it were not in\nthe isspace class - for example, if IFS consists of two  tab  characters,  then\ntwo adjacent tab characters delimit an empty field.\n\nJOBMAX This  variable  defines the maximum number running background jobs that can run\nat a time.  When this limit is reached, the shell will wait for a job  to  com‐\nplete before starting a new job.\n\nLANG   This  variable determines the locale category for any category not specifically\nselected with a variable starting with LC or LANG.\n\nLCALL This variable overrides the value of the LANG variable and any other LC  vari‐\nable.\n\nLCCOLLATE\nThis  variable  determines the locale category for character collation informa‐\ntion.\n\nLCCTYPE\nThis variable determines the locale category for character handling  functions.\nIt  determines  the character classes for pattern matching (see Pathname Expan‐\nsion below).\n\nLCNUMERIC\nThis variable determines the locale category for the decimal point character.\n\nMAIL   If this variable is set to the name of a mail file and the MAILPATH variable is\nnot set, then the shell informs the user of arrival of mail  in  the  specified\nfile.\n\nMAILCHECK\nThis variable specifies how often (in seconds) the shell will check for changes\nin  the modification time of any of the files specified by the MAILPATH or MAIL\nvariables.  The default value is 600 seconds.  When the time  has  elapsed  the\nshell will check before issuing the next prompt.\n\nMAILPATH\nA  colon ( : ) separated list of file names.  If this variable is set, then the\nshell informs the user of any modifications to the specified  files  that  have\noccurred  within the last MAILCHECK seconds.  Each file name can be followed by\na ?  and a message that will be printed.  The message  will  undergo  parameter\nexpansion,  command substitution, and arithmetic expansion with the variable $\ndefined as the name of the file that has changed.  The default message  is  you\nhave mail in $.\n\nPATH   The  search  path  for commands (see Execution below).  The user may not change\nPATH if executing under rksh (except in .profile).\n\nPS1    Every time a new command line is started on an interactive shell, the value  of\nthis  variable  is expanded to resolve backslash escaping, parameter expansion,\ncommand substitution, and arithmetic expansion.  The result defines the primary\nprompt string for that command line.  The default is ``$ ''.  The  character  !\nin the primary prompt string is replaced by the command number (see Command Re-\nentry  below).   Two successive occurrences of !  will produce a single !  when\nthe prompt string is printed.  Note that any terminal escape sequences used  in\nthe PS1 prompt thus need every instance of !  in them to be changed to !!.\n\nPS2    Secondary prompt string, by default ``> ''.\n\nPS3    Selection prompt string used within a select loop, by default ``#? ''.\n\nPS4    The  value  of this variable is expanded for parameter evaluation, command sub‐\nstitution, and arithmetic expansion and precedes  each  line  of  an  execution\ntrace.   By  default, PS4 is ``+ ''.  In addition when PS4 is unset, the execu‐\ntion trace prompt is also ``+ ''.\n\nSHELL  The pathname of the shell is kept in the environment.  At  invocation,  if  the\nbasename  of  this  variable  is rsh, rksh, or krsh, then the shell becomes re‐\nstricted.\n\nTIMEFORMAT\nThe value of this parameter is used as a format string specifying how the  tim‐\ning  information  for  pipelines prefixed with the time reserved word should be\ndisplayed.  The % character introduces a format sequence that is expanded to  a\ntime  value  or other information.  The format sequences and their meanings are\nas follows.\n%%        A literal %.\n%[p][l]R  The elapsed time in seconds.\n%[p][l]U  The number of CPU seconds spent in user mode.\n%[p][l]S  The number of CPU seconds spent in system mode.\n%P        The CPU percentage, computed as (U + S) / R.\n\nThe brackets denote optional portions.  The optional p is  a  digit  specifying\nthe  precision, the number of fractional digits after a decimal point.  A value\nof 0 causes no decimal point or fraction to be output.  At  most  three  places\nafter  the  decimal  point  can  be  displayed;  values of p greater than 3 are\ntreated as 3.  If p is not specified, the value 3 is used.\n\nThe optional l specifies a longer format, including hours if greater than zero,\nminutes, and seconds of the form  HHhMMmSS.FFs.   The  value  of  p  determines\nwhether  or  not  the fraction is included.  Seconds are zero-padded unless the\nposix shell option is on.\n\nAll other characters are output without change and a trailing newline is added.\nIf      the      variable      is      unset,      the      default      value,\n$'\\nreal\\t%2lR\\nuser\\t%2lU\\nsys\\t%2lS',  is  used.   If  the value is empty, no\ntiming information is displayed.\n\nTMOUT  Terminal read timeout. If set to a value greater than zero, the  read  built-in\ncommand and the select compound command time out after TMOUT seconds when input\nis from a terminal.  An interactive shell will issue a warning and allow for an\nextra  60  second  timeout grace period before terminating if a line is not en‐\ntered within the prescribed number of seconds while reading  from  a  terminal.\n(Note  that the shell can be compiled with a maximum bound for this value which\ncannot be exceeded.)\n\nVISUAL The value of this variable is scanned when the shell is  invoked  and  whenever\nits value is changed; if it is found to match certain patterns, the correspond‐\ning  line  editor  (see  In-line  Editing  Options  below) is activated.  If it\nmatches the pattern *[Vv][Ii]*, the vi option is turned on; else if it  matches\nthe pattern *gmacs*, the gmacs option is turned on; else if it matches the pat‐\ntern  *macs*,  the  emacs  option is turned on.  If none of the patterns match,\nemacs is turned on by default upon initializing an interactive shell.   If  the\nvalue  is  changed by assignment and none of the patterns match, no options are\nchanged.  The value of VISUAL overrides the value of EDITOR.\n\nThe shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT, TMOUT and IFS,\nwhile HOME, SHELL, ENV, histchars, and MAIL are not set at all by the shell (although HOME is\nset by login(1)).  On some systems MAIL and SHELL are also set by login(1).\n"
                },
                {
                    "name": "Field Splitting.",
                    "content": "After parameter expansion and command substitution, the results of substitutions are  scanned\nfor  the field separator characters (those found in IFS) and split into distinct fields where\nsuch characters are found.  Explicit empty fields (\"\" or ′′) are  retained.   Implicit  empty\nfields  (those  resulting  from parameters that are unset or have empty string values or from\ncommand substitutions yielding the empty string, and that are not quoted  with  \"\")  are  re‐\nmoved.\n"
                },
                {
                    "name": "Brace Expansion.",
                    "content": "If  the  braceexpand  (-B) option is set then each word, as well as any fields resulting from\nfield splitting (see above), are checked to see if they contain one or more of the brace pat‐\nterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,  or  {n1..n2  ..n3%fmt}  ,\nwhere  *  represents any character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt\nis a format specified as used by printf.  In each case, fields are created by prepending  the\ncharacters  before the { and appending the characters after the } to each of the strings gen‐\nerated by the characters between the { and }.  The resulting fields are  checked  to  see  if\nthey have any brace patterns.\n\nIn  the  first form, a field is created for each string between { and ,, between , and ,, and\nbetween , and }.  The string represented by * can contain embedded matching { and  }  without\nquoting.  Otherwise, each { and } with * must be quoted.\n\nIn  the  seconds form, l1 and l2 must both be either upper case or both be lower case charac‐\nters in the C locale.  In this case a field is created for each character from l1 through l2.\n\nIn the remaining forms, a field is created for each number starting at n1 and continuing  un‐\ntil it reaches n2 incrementing n1 by n3.  The cases where n3 is not specified behave as if n3\nwhere 1 if n1<=n2 and -1 otherwise.  If forms which specify %fmt any format flags, widths and\nprecisions  can  be specified and fmt can end in any of the specifiers cdiouxX.  For example,\n{a,z}{1..5..3%02d}{b..c}x expands to the 8 fields, a01bx, a01cx, a04bx, a04cx, z01bx,  z01cx,\nz04bx and z04cx.\n"
                },
                {
                    "name": "Pathname Expansion.",
                    "content": "This  is also known as globbing or sometimes filename generation.  Pathname expansion is dis‐\nabled if the -f a.k.a.  --noglob shell option is on.  Otherwise, if certain  special  charac‐\nters  are  found in a word or in a field resulting from field splitting (see above), then the\nword or field is regarded as a pattern.  Each literal word is scanned for the  characters  *,\n?, [, and (, but fields resulting from field splitting are scanned only for the characters *,\n?, and [ for compatibility reasons (in which case the ( character is not special and any pat‐\ntern syntax described below that involves parentheses does not apply).\n\nEach file name component that contains a recognized pattern character is replaced with a lex‐\nicographically  sorted set of names that matches the pattern from that directory.  If no file\nname is found that matches the pattern, then that component of the filename is left unchanged\nunless the pattern is prefixed with ∼(N), in which case it is  removed  as  described  below.\nThe  special traversal names .  and ..  are never matched.  If FIGNORE is set, then each file\nname component that matches the pattern defined by the value of FIGNORE is ignored when  gen‐\nerating the matching filenames.  If FIGNORE is not set, the character .  at the start of each\nfile  name  component will be ignored unless the first character of the pattern corresponding\nto this component is the character .  itself.  Note that, for uses of pattern matching  other\nthan pathname expansion, the / and .  are not treated specially.\n\n*      Matches  any string, including the empty string.  When used for filename expan‐\nsion, if the globstar option is on, an isolated pattern of two adjacent *s will\nmatch all files and zero or more directories and subdirectories.   If  followed\nby a / then only directories and subdirectories will match.\n?      Matches any single character.\n[...]  Matches  any one of the enclosed characters.  A pair of characters separated by\n- matches any character lexically between the pair, inclusive.   If  the  first\ncharacter following the opening [ is a !  or ^, then any character not enclosed\nis  matched.   A  -  can  be included in the character set by putting it as the\nfirst or last character.\nWithin [ and ], character classes can be specified with the  syntax  [:class:],\nwhere  class  is  one  of  the following classes defined in the ANSI C standard\n(note that word is equivalent to alnum plus the character ):\nalnum alpha blank cntrl digit graph lower print punct space upper word xdigit\nWithin [ and ], an equivalence class can be specified  with  the  syntax  [=c=]\nwhich matches all characters with the same primary collation weight (as defined\nby the current locale) as the character c.  Within [ and ], [.symbol.]  matches\nthe collating symbol symbol.\n\nA  pattern-list is a list of one or more patterns separated from each other with a & or |.  A\n& signifies that all patterns must be matched whereas | requires that  only  one  pattern  be\nmatched.  Composite patterns can be formed with one or more of the following subpatterns:\n?(pattern-list)\nOptionally matches any one of the given patterns.\n*(pattern-list)\nMatches zero or more occurrences of the given patterns.\n+(pattern-list)\nMatches one or more occurrences of the given patterns.\n{n}(pattern-list)\nMatches n occurrences of the given patterns.\n{m,n}(pattern-list)\nMatches from m to n occurrences of the given patterns.  If m is omitted, 0 will\nbe used.  If n is omitted, at least m occurrences will be matched.\n@(pattern-list)\nMatches exactly one of the given patterns.\n!(pattern-list)\nMatches anything except one of the given patterns.\n\nBy default, each pattern or subpattern will match the longest string possible consistent with\ngenerating  the  longest overall match.  If more than one match is possible, the one starting\nclosest to the beginning of the string will be chosen.   However, for each of the above  com‐\npound  patterns,  a  -  can  be inserted in front of the ( to cause the shortest match to the\nspecified pattern-list to be used.\n\nWhen pattern-list is contained within parentheses, the backslash character \\ is treated  spe‐\ncially  even when inside a character class.   All ANSI C character escapes are recognized and\nmatch the specified character.  In addition, the following escape sequences are recognized:\n\\d     Matches any character in the digit class.\n\\D     Matches any character not in the digit class.\n\\s     Matches any character in the space class.\n\\S     Matches any character not in the space class.\n\\w     Matches any character in the word class.\n\\W     Matches any character not in the word class.\n\nA pattern of the form %(pattern-pair(s)) is a subpattern that can be  used  to  match  nested\ncharacter  expressions.   Each pattern-pair is a two-character sequence that cannot contain &\nor |.  The first pattern-pair specifies the starting and ending  characters  for  the  match.\nEach subsequent pattern-pair represents the beginning and ending characters of a nested group\nthat  will be skipped over when counting starting and ending character matches.  The behavior\nis unspecified when the first character of a pattern-pair is  alphanumeric,  except  for  the\nfollowing:\nD      Causes  the  ending  character to terminate the search for this pattern without\nfinding a match.\nE      Causes the ending character to be interpreted as an escape character.\nL      Causes the ending character to be interpreted as a quote character, causing all\ncharacters to be ignored when looking for a match.\nQ      Causes the ending character to be interpreted as a quote character, causing all\ncharacters other than any escape character to be ignored  when  looking  for  a\nmatch.\n\nThus, %({}Q\"E\\), matches characters starting at { until the matching } is found, not counting\nany  {  or  }  that  is  inside a double-quoted string or preceded by the escape character \\.\nWithout the {}, this pattern matches any C language string.\n\nEach subpattern in a composite pattern is numbered, starting at 1, by the location of  the  (\nwithin  the  pattern.   The sequence \\n, where n is a single digit and \\n comes after the nth\nsubpattern, matches the same string as the subpattern itself.\n\nFinally, a pattern can contain subpatterns of the form ∼(options:pattern-list), where  either\noptions  or  :pattern-list can be omitted.  Unlike the other compound patterns, these subpat‐\nterns are not counted in the numbered subpatterns.  :pattern-list must be omitted for options\nE, F, G, N, P, V, and X below.  If options is present, it can consist of one or more  of  the\nfollowing:\n+      Enable the following options.  This is the default.\n-      Disable the following options.\nE      The  remainder  of the pattern uses extended regular expression syntax like the\n-E option of the grep(1) command.\nF      The remainder of the pattern uses the fixed pattern syntax of the -F option  of\nthe grep(1) command.\nG      The  remainder  of  the  pattern  uses basic regular expression syntax like the\ngrep(1) command without options.\nK      The remainder of the pattern uses shell pattern syntax.  This is the default.\nN      When it is the first letter and is used with pathname expansion, and no matches\noccur, the file pattern expands to the empty string instead of remaining  unex‐\npanded.  Otherwise, it is ignored.\nX      The  remainder of the pattern uses augmented regular expression syntax like the\n-X option of the AT&T AST version of the grep(1) command.\nP      The remainder of the pattern uses perl(1) regular expression syntax.   Not  all\nperl regular expression syntax is currently implemented.\nV      The remainder of the pattern uses System V regular expression syntax.\ni      Always  treat  the  match as case-insensitive, regardless of the globcasedetect\nshell option.\ng      File the longest match (greedy).  This is the default.\nl      Left-anchor the pattern.  This is the default for K style patterns.\nr      Right-anchor the pattern.  This is the default for K style patterns.\n\nIf both options and :pattern-list are specified, then the options  apply  only  to   pattern-\nlist.   Otherwise,  these  options  remain  in effect until they are disabled by a subsequent\n∼(...) or at the end of the subpattern containing ∼(...).\n"
                },
                {
                    "name": "Quoting.",
                    "content": "Each of the metacharacters listed earlier (see Definitions above) has a  special  meaning  to\nthe  shell  and causes termination of a word unless quoted.  A character may be quoted (i.e.,\nmade to stand for itself) by preceding it with a \\.  The  pair  \\new-line  is  removed.   All\ncharacters enclosed between a pair of single quote marks (′′) that is not preceded by a $ are\nquoted.   A single quote cannot appear within the single quotes.  A single quoted string pre‐\nceded by an unquoted $ is processed as an ANSI C string except for the following:\n\\0     Causes the remainder of the string to be ignored.\n\\E     Equivalent to the escape character (ASCII 033),\n\\e     Equivalent to the escape character (ASCII 033),\n\\cx    Expands to the character control-x.\n\\C[.name.]\nExpands to the collating element name.\n\nInside double quote marks (\"\"), parameter and command substitution occur  and  \\  quotes  the\ncharacters \\, `, \", and $.  A $ in front of a double quoted string will be ignored in the \"C\"\nor \"POSIX\" locale, and may cause the string to be replaced by a locale specific string other‐\nwise.   The  meaning of $* and $@ is identical when not quoted or when used as a variable as‐\nsignment value or as a file name.  However, when used as a command argument, \"$*\" is  equiva‐\nlent  to  \"$1d$2d...\",  where  d  is the first character of the IFS variable, whereas \"$@\" is\nequivalent to \"$1\" \"$2\" ....  Inside grave quote marks (``), \\ quotes the  characters  \\,  `,\nand $.  If the grave quotes occur within double quotes, then \\ also quotes the character \".\n\nThe  special  meaning of reserved words or aliases can be removed by quoting any character of\nthe reserved word.  The recognition of function names or built-in command names listed  below\ncannot be altered by quoting them.\n"
                },
                {
                    "name": "Arithmetic Evaluation.",
                    "content": "The  shell performs arithmetic evaluation for arithmetic expansion, to evaluate an arithmetic\ncommand, to evaluate an indexed array subscript, and to evaluate arguments  to  the  built-in\ncommands  shift  and let as well as arguments to numeric format specifiers given to print -f\nand printf.  Evaluations are performed using double precision floating  point  arithmetic  or\nlong double precision floating point for systems that provide this data type.  Floating point\nconstants follow the ANSI C programming language floating point conventions.  The case-insen‐\nsitive  floating  point constants NaN and Inf can be used to represent \"not a number\" and in‐\nfinity respectively, unless the posix shell option is on.  Integer constants follow the  ANSI\nC  programming language integer constant conventions although only single byte character con‐\nstants are recognized and character casts are not recognized.  In addition constants  can  be\nof  the  form [base#]n where base is a decimal number between two and sixty-four representing\nthe arithmetic base and n is a number in that base.  The digits above 9  are  represented  by\nthe  lower  case letters, the upper case letters, @, and  respectively.  For bases less than\nor equal to 36, upper and lower case characters can be used interchangeably.\n\nAn arithmetic expression uses the same syntax, precedence, and associativity of expression as\nthe C language.  All the C language operators that apply to floating point quantities can  be\nused.  In addition, the operator  can be used for exponentiation.  It has higher precedence\nthan  multiplication  and  is left associative.  In addition, when the value of an arithmetic\nvariable or subexpression can be represented as a long integer, all C language integer arith‐\nmetic operations can be performed.  Variables can be referenced by name within an  arithmetic\nexpression  without using the parameter expansion syntax.  When a variable is referenced, its\nvalue is evaluated as an arithmetic expression.\n\nAny of the following math library functions that are in the C math library can be used within\nan arithmetic expression:\n"
                },
                {
                    "name": "abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh  erf  erfc  exp  exp10",
                    "content": ""
                },
                {
                    "name": "exp2 expm1 fabs fdim finite float floor fma fmax fmin fmod fpclass fpclassify hypot ilogb int",
                    "content": ""
                },
                {
                    "name": "isfinite isgreater isgreaterequal isinf isinfinite isless islessequal islessgreater isnan is‐",
                    "content": ""
                },
                {
                    "name": "normal  issubnormal  isunordered iszero j0 j1 jn ldexp lgamma log log10 log1p log2 logb near‐",
                    "content": ""
                },
                {
                    "name": "byint nextafter nexttoward pow remainder rint round scalb scalbn signbit sin  sinh  sqrt  tan",
                    "content": ""
                },
                {
                    "name": "tanh tgamma trunc y0 y1 yn",
                    "content": "In  addition,  arithmetic  functions  can be defined as shell functions with a variant of the\nfunction name syntax,\n\nfunction .sh.math.name ident ... { list ;}\nwhere name is the function name used in the arithmetic expression and each identifier,\nident is a name reference to the long double precision floating point  argument.   The\nvalue  of .sh.value when the function returns is the value of this function.  User de‐\nfined functions can take up to 3 arguments and override C math library functions.\n\nAn internal representation of a variable as a double precision floating point can  be  speci‐\nfied  with the -E [n], -F [n], or -X [n] option of the typeset special built-in command.  The"
                },
                {
                    "name": "-E",
                    "content": "it  is  expanded.   The optional option argument n defines the number of significant figures.\nThe -F option causes the expansion to be represented as a floating decimal number when it  is\nexpanded.   The  -X option causes the expansion to be represented using the %a format defined\nby ISO C-99.  The optional option argument n defines the number of places after  the  decimal\n(or radix) point in this case.\n\nAn  internal  integer representation of a variable can be specified with the -i [n] option of\nthe typeset special built-in command.  The optional option argument n specifies an arithmetic\nbase to be used when expanding the variable.  If you do not specify an arithmetic base,  base\n10 will be used.\n\nArithmetic evaluation is performed on the value of each assignment to a variable with the -E,",
                    "flag": "-E"
                },
                {
                    "name": "-F -X -i",
                    "content": "integer causes the fractional part to be truncated.\n",
                    "flag": "-i"
                },
                {
                    "name": "Prompting.",
                    "content": "When used interactively, the shell prompts with the value of PS1 after expanding it for para‐\nmeter expansion, command substitution, and arithmetic expansion, before  reading  a  command.\nIn  addition,  each  single !  in the prompt is replaced by the command number.  A !!  is re‐\nquired to place !  in the prompt.  If at any time a new-line is typed and  further  input  is\nneeded to complete a command, then the secondary prompt (i.e., the value of PS2) is issued.\n"
                },
                {
                    "name": "Conditional Expressions.",
                    "content": "A conditional expression is used with the [[ compound command to test attributes of files and\nto  compare  strings.   Field splitting and pathname expansion are not performed on the words\nbetween [[ and ]].  Each expression can be constructed from one  or  more  of  the  following\nunary or binary expressions:\nstring Same as -n string below.\n-a file\nSame as -e below.  This is obsolete.\n-b file\nTrue if file exists and is a block special file.\n-c file\nTrue if file exists and is a character special file.\n-d file\nTrue if file exists and is a directory.\n-e file\nTrue if file exists.\n-f file\nTrue if file exists and is an ordinary file.\n-g file\nTrue if file exists and it has its setgid bit set.\n-k file\nTrue if file exists and it has its sticky bit set.\n-n string\nTrue if length of string is non-zero.\n-o ?option\nTrue if option named option is a valid option name.\n-o option\nTrue if option named option is on.\n-p file\nTrue if file exists and is a fifo special file or a pipe.\n-r file\nTrue if file exists and is readable by current process.\n-s file\nTrue if file exists and has size greater than zero.\n-t fildes\nTrue  if  file  descriptor number fildes is open and associated with a terminal\ndevice.\n-u file\nTrue if file exists and it has its setuid bit set.\n-v name\nTrue if variable name is a valid variable name and is set.\n-w file\nTrue if file exists and is writable by current process.\n-x file\nTrue if file exists and is executable by current process.  If file  exists  and\nis  a  directory,  then true if the current process has permission to search in\nthe directory.\n-z string\nTrue if length of string is zero.\n-L file\nTrue if file exists and is a symbolic link.\n-h file\nTrue if file exists and is a symbolic link.\n-N file\nTrue if file exists and the modification time is greater than the  last  access\ntime.\n-O file\nTrue if file exists and is owned by the effective user ID of this process.\n-G file\nTrue  if  file  exists  and  its  group  matches the effective group ID of this\nprocess.\n-R name\nTrue if variable name is a name reference.\n-S file\nTrue if file exists and is a socket.\nfile1 -nt file2\nTrue if file1 exists and file2 does not, or file1 is newer than file2.\nfile1 -ot file2\nTrue if file2 exists and file1 does not, or file1 is older than file2.\nfile1 -ef file2\nTrue if file1 and file2 exist and refer to the same file.\nstring == pattern\nTrue if string matches pattern.  Any part of pattern can be quoted to cause  it\nto be matched as a string.  With a successful match to a pattern, the .sh.match\narray variable will contain the match and subpattern matches.\nstring = pattern\nSame as == above, but is obsolete.\nstring != pattern\nTrue if string does not match pattern.  When the string matches the pattern the\n.sh.match array variable will contain the match and subpattern matches.\nstring =∼ ere\nTrue if string matches the pattern ∼(E)ere where ere is an extended regular ex‐\npression.\nstring1 < string2\nTrue if string1 comes before string2 based on ASCII value of their characters.\nstring1 > string2\nTrue if string1 comes after string2 based on ASCII value of their characters.\n\nThe following obsolete arithmetic comparisons are also permitted:\nexp1 -eq exp2\nTrue if exp1 is equal to exp2.\nexp1 -ne exp2\nTrue if exp1 is not equal to exp2.\nexp1 -lt exp2\nTrue if exp1 is less than exp2.\nexp1 -gt exp2\nTrue if exp1 is greater than exp2.\nexp1 -le exp2\nTrue if exp1 is less than or equal to exp2.\nexp1 -ge exp2\nTrue if exp1 is greater than or equal to exp2.\n\nIn  each  of  the above expressions, if file is of the form /dev/fd/n, where n is an integer,\nthen the test is applied to the open file whose descriptor number is n.  The posix shell  op‐\ntion disables this special handling.\n\nA compound expression can be constructed from these primitives by using any of the following,\nlisted in decreasing order of precedence:\n(expression)\nTrue if expression is true.  Used to group expressions.\n! expression\nTrue if expression is false.\nexpression1 && expression2\nTrue if expression1 and expression2 are both true.\nexpression1 || expression2\nTrue if either expression1 or expression2 is true.\n"
                },
                {
                    "name": "Input/Output.",
                    "content": "Before a command is executed, its input and output may be redirected using a special notation\ninterpreted  by the shell.  The following may appear anywhere in a simple-command or may pre‐\ncede or follow a command and are not passed on to the invoked command.  Command substitution,\nparameter expansion, and arithmetic expansion occur before word or digit is  used  except  as\nnoted  below.   Pathname  expansion  occurs  only if the shell is interactive and the pattern\nmatches a single file.  Field splitting is not performed.\n\nIn each  of  the  following  redirections,  if  file  is  of  the  form  /dev/sctp/host/port,\n/dev/tcp/host/port, or /dev/udp/host/port, where host is a hostname or host address, and port\nis a service given by name or an integer port number, then the redirection attempts to make a\ntcp, sctp or udp connection to the corresponding socket.\n\nNo intervening space is allowed between the characters of redirection operators.\n\n<word         Use file word as standard input (file descriptor 0).\n\n>word         Use file word as standard output (file descriptor 1).  If the file does not ex‐\nist  then  it  is created.  If the file exists, and the noclobber option is on,\nthis causes an error; otherwise, it is truncated to zero length.\n\n>|word        Same as >, except that it overrides the noclobber option.\n\n>;word        Write output to a temporary file.  If the command completes successfully rename\nit to word, otherwise, delete the temporary file.  >;word cannot be  used  with\nthe exec and redirect built-ins.\n\n>>word        Use  file word as standard output.  If the file exists, then output is appended\nto it (by first seeking to the end-of-file); otherwise, the file is created.\n\n<>word        Open file word for reading and writing as standard output.  If the posix option\nis active, it defaults to standard input instead.\n\n<>;word       The same as <>word except that if the command completes successfully,  word  is\ntruncated to the offset at command completion.  <>;word cannot be used with the\nexec and redirect built-ins.\n\n<<[-]word     The shell input is read up to a line that is the same as word after any quoting\nhas  been  removed, or to an end-of-file.  No parameter expansion, command sub‐\nstitution, arithmetic expansion or pathname expansion  is  performed  on  word.\nThe resulting document, called a here-document, becomes the standard input.  If\nany  character  of  word  is  quoted, then no interpretation is placed upon the\ncharacters of the document; otherwise, parameter expansion,  command  substitu‐\ntion,  and arithmetic expansion occur, \\new-line is ignored, and \\ must be used\nto quote the characters \\, $, `.  If - is appended to <<, then all leading tabs\nare stripped from word and from the document.  If # is  appended  to  <<,  then\nleading spaces and tabs will be stripped off the first line of the document and\nup  to  an equivalent indentation will be stripped from the remaining lines and\nfrom word.  A tab stop is assumed to occur at every 8 columns for the  purposes\nof determining the indentation.\n\n<<<word       A  short  form of here document in which word becomes the contents of the here-\ndocument after any parameter expansion, command  substitution,  and  arithmetic\nexpansion occur.\n\n<&digit       The standard input is duplicated from file descriptor digit (see dup(2)).\n\n>&digit       The standard output is duplicated from file descriptor digit.\n\n<&digit-      The file descriptor given by digit is moved to standard input.\n\n>&digit-      The file descriptor given by digit is moved to standard output.\n\n<&-           The standard input is closed.\n\n>&-           The standard output is closed.\n\n<&p           The input from the co-process is moved to standard input.\n\n>&p           The output to the co-process is moved to standard output.\n\n<#((expr))    Evaluate  arithmetic  expression expr and position file descriptor 0 to the re‐\nsulting value bytes from the start of the file.   The  variables  CUR  and  EOF\nevaluate  to the current offset and end-of-file offset respectively when evalu‐\nating expr.\n\n>#((offset))  The same as <# except applies to file descriptor 1.\n\n<#pattern     Seeks forward to the beginning of the next line containing pattern.\n\n<##pattern    The same as <# except that the portion of the file that is skipped is copied to\nstandard output.\n\nIf one of the above is preceded by a digit, with no intervening space, then the file descrip‐\ntor number referred to is that specified by the digit (instead of the default 0  or  1).   If\none  of  the  above, other than >&- and the ># and <# forms, is preceded by {varname} with no\nintervening space, then a file descriptor number > 9 will be selected by the shell and stored\nin the variable varname, so it can be read from or written to with redirections like <& $var‐\nname or >& $varname.  If >&- or the any of the ># and <# forms is preceded by  {varname}  the\nvalue of varname defines the file descriptor to close or position.  For example:\n\n... 2>&1\n\nmeans file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and\n\nexec {n}<file\n\nmeans open file named file for reading and store the file descriptor number in variable n.\n\nA special shorthand redirection operator &>word is available; it is equivalent to >word 2>&1.\nIt  cannot be preceded by any digit or variable name. This shorthand is disabled if the posix\nshell option is active.\n\nThe order in which redirections are specified is significant.  The shell evaluates each redi‐\nrection in terms of the (file descriptor, file) association at the time of  evaluation.   For\nexample:\n\n... 1>fname 2>&1\n\nfirst  associates  file  descriptor  1 with file fname.  It then associates file descriptor 2\nwith the file associated with file descriptor 1 (i.e.  fname).  If the order of  redirections\nwere  reversed,  file  descriptor  2 would be associated with the terminal (assuming file de‐\nscriptor 1 had been) and then file descriptor 1 would be associated with file fname.\n\nIf a command is followed by & and job control is not active, then the default standard  input\nfor the command is the empty file /dev/null.  Otherwise, the environment for the execution of\na  command  contains  the  file descriptors of the invoking shell as modified by input/output\nspecifications.\n"
                },
                {
                    "name": "Environment.",
                    "content": "The environment (see environ(7)) is a list of name-value pairs that is passed to an  executed\nprogram  in  the  same  way as a normal argument list.  The names must be identifiers and the\nvalues are character strings.  The shell interacts with the environment in several ways.   On\ninvocation,  the shell scans the environment and creates a variable for each name found, giv‐\ning it the corresponding value and attributes and marking it export.  Executed  commands  in‐\nherit  the  environment.   If  the user modifies the values of these variables or creates new\nones, using the export or typeset -x commands, they become part of the environment.  The  en‐\nvironment  seen  by  any executed command is thus composed of any name-value pairs originally\ninherited by the shell, whose values may be modified by the current shell, plus any additions\nwhich must be noted in export or typeset -x commands.\n\nThe environment for any simple-command or function may be augmented by prefixing it with  one\nor  more  variable assignments.  A variable assignment argument is a word of the form identi‐\nfier=value.  Thus:\n\nTERM=450 cmd args                  and\n(export TERM; TERM=450; cmd args)\n\nare equivalent (as far as the above execution of cmd is concerned except for special built-in\ncommands listed below - those that are marked with †).\n\nIf the obsolete -k option is set, all variable assignment arguments are placed in  the  envi‐\nronment,  even  if  they  occur after the command name.  The following first prints a=b c and\nthen c:\n\necho a=b c\nset -k\necho a=b c\n\nThis feature is intended for use with scripts written for early versions of the shell and its\nuse in new scripts is strongly discouraged.  It is likely to disappear someday.\n"
                },
                {
                    "name": "Functions.",
                    "content": "For historical reasons, there are two ways to define functions, the  name()  syntax  and  the\nfunction  name  syntax, described in the Commands section above.  Shell functions are read in\nand stored internally.  Alias names are resolved when the function is  read.   Functions  are\nexecuted  like  commands  with the arguments passed as positional parameters.  (See Execution\nbelow.)\n\nFunctions defined by the function name syntax and called by name execute in the same  process\nas  the  caller  and  share  all  files and present working directory with the caller.  Traps\ncaught by the caller are reset to their default action inside the function.  A trap condition\nthat is not caught or ignored by the function causes the function to terminate and the condi‐\ntion to be passed on to the caller.  A trap on EXIT set inside a function is executed in  the\nenvironment of the caller after the function completes.  Ordinarily, variables are shared be‐\ntween  the  calling  program and the function.  However, the typeset special built-in command\nused within a function defines local variables whose scope  includes  the  current  function.\nThey  can be passed to functions that they call in the variable assignment list that precedes\nthe call or as arguments passed as name references.  Errors within functions  return  control\nto the caller.\n\nFunctions  defined with the name() syntax and functions defined with the function name syntax\nthat are invoked with the .  special built-in are executed in the  caller's  environment  and\nshare all variables and traps with the caller.  Errors within these function executions cause\nthe script that contains them to abort.\n\nThe special built-in command return is used to return from function calls.\n\nFunction  names  can  be listed with the -f or +f option of the typeset special built-in com‐\nmand.  The text of functions, when available, will also be listed with -f.  Functions can  be\nundefined with the -f option of the unset special built-in command.\n\nOrdinarily,  functions are unset when the shell executes a shell script.  Functions that need\nto be defined across separate invocations of the shell should be placed in  a  directory  and\nthe  FPATH variable should contain the name of this directory.  They may also be specified in\nthe ENV file.\n"
                },
                {
                    "name": "Discipline Functions.",
                    "content": "Each variable can have zero or more discipline functions associated with it.  The shell  ini‐\ntially  understands  the  discipline  names get, set, append, and unset but can be added when\ndefining new types.  On most systems others can be added at run time via  the  C  programming\ninterface  extension  provided by the builtin built-in utility.  If the get discipline is de‐\nfined for a variable, it is invoked whenever the given variable is referenced.  If the  vari‐\nable  .sh.value  is  assigned a value inside the discipline function, the referenced variable\nwill evaluate to this value instead.  If the set discipline is defined for a variable, it  is\ninvoked whenever the given variable is assigned a value.  If the append discipline is defined\nfor  a variable, it is invoked whenever a value is appended to the given variable.  The vari‐\nable .sh.value is given the value of the variable before invoking  the  discipline,  and  the\nvariable  will  be  assigned  the  value  of  .sh.value  after  the discipline completes.  If\n.sh.value is unset inside the discipline, then that value is unchanged.  If the unset  disci‐\npline is defined for a variable, it is invoked whenever the given variable is unset.\n\nThe  variable .sh.name contains the name of the variable for which the discipline function is\ncalled, .sh.subscript is the subscript of the variable, and .sh.value will contain the  value\nbeing  assigned  inside  the  set  discipline function.  The variable  is a reference to the\nvariable including the subscript if any.  For the set  discipline,  changing  .sh.value  will\nchange  the  value  that gets assigned.  Finally, the expansion ${var.name}, when name is the\nname of a discipline, and there is no variable of this name, is  equivalent  to  the  command\nsubstitution ${ var.name;}.\n\n"
                },
                {
                    "name": "Name Spaces.",
                    "content": "Commands and functions that are executed as part of the list of a namespace command that mod‐\nify  variables  or  create new ones, create a new variable whose name is the name of the name\nspace as given by identifier preceded by ..  When a variable whose name  is  name  is  refer‐\nenced,  it  is first searched for using .identifier.name.  Similarly, a function defined by a\ncommand in the namespace list is created using the name space name preceded by a ..\n\nWhen the list of a namespace command contains a namespace command, the names of variables and\nfunctions that are created consist of the variable or function name preceded by the  list  of\nidentifiers each preceded by ..\n\nOutside of a name space, a variable or function created inside a name space can be referenced\nby preceding it with the name space name.\n\nBy default, variables starting with .sh are in the sh name space.\n\n"
                },
                {
                    "name": "Type Variables.",
                    "content": "Typed  variables  provide  a way to create data structure and objects.  A type can be defined\neither by a shared library, by the enum built-in command described below, or by using the new"
                },
                {
                    "name": "-T  -T",
                    "content": "specified  as  an  option argument to -T, is set with a compound variable assignment that de‐\nfines the type.  Function definitions can appear inside the compound variable assignment  and\nthese  become  discipline functions for this type and can be invoked or redefined by each in‐\nstance of the type.  The function name create is treated specially.  It is invoked  for  each\ninstance  of  the  type that is created but is not inherited and cannot be redefined for each\ninstance.\n\nWhen a type is defined a special built-in command of that name is added.  These built-ins are\ndeclaration commands and follow the same expansion rules as the built-in  commands  described\nbelow that are marked with a ‡ symbol. These commands can subsequently be used inside further\ntype definitions.  The man page for these commands can be generated by using the --man option\nor any of the other -- options described with getopts.  The -r, -a, -A, -h, and -S options of\ntypeset are permitted with each of these new built-ins.\n\nAn  instance  of a type is created by invoking the type name followed by one or more instance\nnames.  Each instance of the type is initialized with a copy of the subvariables  except  for\nsubvariables  that  are defined with the -S option.  Variables defined with the -S are shared\nby all instances of the type.  Each instance can change the value of any subvariable and  can\nalso  define  new discipline functions of the same names as those defined by the type defini‐\ntion as well as any standard discipline names.  No additional subvariables can be defined for\nany instance.\n\nWhen defining a type, if the value of a subvariable is not set and the -r attribute is speci‐\nfied, it causes the subvariable to be a required subvariable.  Whenever an instance of a type\nis created, all required subvariables must be specified.  These subvariables become read-only\nin each instance.\n\nWhen unset is invoked on a subvariable within a type, and the -r attribute has not been spec‐\nified for this field, the value is reset to the default value associative with the type.  In‐\nvoking unset on a type instance not contained within another type  deletes  all  subvariables\nand the variable itself.\n\nA  type definition can be derived from another type definition by defining the first subvari‐\nable name as  and defining its type as the base type.  Any remaining definitions will be ad‐\nditions and modifications that apply to the new type.  If the new type name is  the  same  as\nthat  of the base type, the type will be replaced and the original type will no longer be ac‐\ncessible.\n\nThe typeset command with the -T and no option argument or operands will write  all  the  type\ndefinitions to standard output in a form that can be read in to create all they types.\n",
                    "flag": "-T"
                },
                {
                    "name": "Jobs.",
                    "content": "If  the monitor option of the set command is turned on, an interactive shell associates a job\nwith each pipeline.  It keeps a table of current jobs, printed by the jobs command,  and  as‐\nsigns  them  small  integer  numbers.  When a job is started asynchronously with &, the shell\nprints a line which looks like:\n\n[1] 1234\n\nindicating that the job which was started asynchronously was job number 1 and had  one  (top-\nlevel) process, whose process ID was 1234.\n\nThis paragraph and the next require features that are not in all versions of UNIX and may not\napply.   If  you are running a job and wish to do something else you may hit the key ^Z (con‐\ntrol-Z) which sends a STOP signal to the current job.  The shell will then normally  indicate\nthat the job has been `Stopped', and print another prompt.  You can then manipulate the state\nof this job, putting it in the background with the bg command, or run some other commands and\nthen  eventually bring the job back into the foreground with the foreground command fg.  A ^Z\ntakes effect immediately and is like an interrupt in that pending output and unread input are\ndiscarded when it is typed.\n\nA job being run in the background will stop if it tries to read  from  the  terminal.   Back‐\nground  jobs  are  normally allowed to produce output, but this can be disabled by giving the\ncommand stty tostop.  If you set this tty option, then background jobs will  stop  when  they\ntry to produce output like they do when they try to read input.\n\nThere  are  several  ways  to  refer  to  jobs in the shell.  A job can be referred to by the\nprocess ID of any process of the job or by one of the following:\n%number\nThe job with the given number.\n%string\nAny job whose command line begins with string.\n%?string\nAny job whose command line contains string.\n%%     Current job.\n%+     Equivalent to %%.\n%-     Previous job.\n\nThe shell learns immediately whenever a process changes state.  It normally informs you when‐\never a job becomes blocked so that no further progress is possible, but only just  before  it\nprints  a  prompt.  This is done so that it does not otherwise disturb your work.  The notify\noption of the set command causes the shell to print these job change messages as soon as they\noccur.\n\nWhen the monitor option is on, each background job that completes triggers any trap  set  for\nCHLD.\n\nWhen  you  try  to leave the shell while jobs are running or stopped, you will be warned that\n`You have stopped(running) jobs.'  You may use the jobs command to see what they are.  If you\nimmediately try to exit again, the shell will not warn you a second  time,  and  the  stopped\njobs  will be terminated.  When a login shell receives a HUP signal, it sends a HUP signal to\neach job that has not been disowned with the disown built-in command described below.\n"
                },
                {
                    "name": "Signals.",
                    "content": "The INT and QUIT signals for an invoked command are ignored if the command is followed  by  &\nand  the  monitor  option is not active.  Otherwise, signals have the values inherited by the\nshell from its parent (but see also the trap built-in command below).\n"
                },
                {
                    "name": "Execution.",
                    "content": "Each time a command is read, the above expansions and substitutions are carried out.  If  the\ncommand name matches one of the Special Built-in Commands listed below, it is executed within\nthe current shell process.  Next, the command name is checked to see if it matches a user de‐\nfined  function.  If it does, the positional parameters are saved and then reset to the argu‐\nments of the function call.  A function is also executed in the current shell process.   When\nthe  function  completes  or issues a return, the positional parameter list is restored.  For\nfunctions defined with the function name syntax, any trap set on EXIT within the function  is\nexecuted.  The exit value of a function is the value of the last command executed.  If a com‐\nmand  name is not a special built-in command or a user defined function, but it is one of the\nbuilt-in commands listed below, it is executed in the current shell process.\n\nThe shell variables PATH followed by the variable FPATH defines the list  of  directories  to\nsearch  for the command name.  Alternative directory names are separated by a colon (:).  The\ndefault path is the value that was output by getconf PATH at the time ksh was compiled.   The\ncurrent  directory  can be specified by two or more adjacent colons, or by a colon at the be‐\nginning or end of the path list.  If the command name contains a /, then the search  path  is\nnot  used.  Otherwise, each directory in the list of directories defined by PATH and FPATH is\nchecked in order.  If the directory being searched is contained in FPATH and contains a  file\nwhose  name  matches  the  command  being searched, then this file is loaded into the current\nshell environment as if it were the argument to the . command except that only preset aliases\nare expanded, and a function of the given name is executed as described above.\n\nIf this directory is not in FPATH the shell first determines whether there is a built-in ver‐\nsion of a command corresponding to a given pathname and if so it is invoked  in  the  current\nprocess.   If  no  built-in is found, the shell checks for a file named .paths in this direc‐\ntory.  If found and there is a line of the form FPATH=path where path names an  existing  di‐\nrectory then that directory is searched immediately after the current directory as if it were\nfound  in  the  FPATH variable.  If path does not begin with /, it is checked for relative to\nthe directory being searched.\n\nThe .paths file is then checked for a line of the form PLUGINLIB=libname [ : libname ] ... .\nEach library named by libname will be searched for as  if  it  were  an  option  argument  to\nbuiltin -f, and if it contains a built-in of the specified name this will be executed instead\nof a command by this name.  Any built-in loaded from a library found this way will be associ‐\nated with the directory containing the .paths file so it will only execute if not found in an\nearlier directory.\n\nFinally, the directory will be checked for a file of the given name.  If the file has execute\npermission but is not an a.out file, it is assumed to be a file containing shell commands.  A\nseparate  shell  is spawned to read it.  All non-exported variables are removed in this case.\nIf the shell command file doesn't have read permission, or if the setuid and/or  setgid  bits\nare  set  on the file, then the shell executes an agent whose job it is to set up the permis‐\nsions and execute the shell with the shell command file passed down as an open file.  If  the\n.paths  contains a line of the form name=value in the first or second line, then the environ‐\nment variable name is modified by prepending the directory specified by value to  the  direc‐\ntory  list.  If value is not an absolute directory, then it specifies a directory relative to\nthe directory that the executable was found.  If the environment variable name does  not  al‐\nready  exist it will be added to the environment list for the specified command.  A parenthe‐\nsized command is executed in a subshell without removing non-exported variables.\n"
                },
                {
                    "name": "Command Re-entry.",
                    "content": "The text of the last HISTSIZE (default 512) commands entered from a terminal device is  saved\nin a history file.  The file $HOME/.shhistory is used if the HISTFILE variable is not set or\nif  the  file  it  names is not writable.  A shell can access the commands of all interactive\nshells which use the same named HISTFILE.  The built-in command hist is used to list or  edit\na  portion  of  this file.  The portion of the file to be edited or listed can be selected by\nnumber or by giving the first character or characters of the command.  A  single  command  or\nrange  of  commands can be specified.  If you do not specify an editor program as an argument\nto hist then the value of the variable HISTEDIT is used.  If HISTEDIT is unset, the  obsolete\nvariable  FCEDIT  is  used.  If FCEDIT is not defined, then /bin/ed is used.  The edited com‐\nmand(s) is printed and re-executed upon leaving the editor unless you quit  without  writing.\nThe -s option (and in obsolete versions, the editor name -) is used to skip the editing phase\nand to re-execute the command.  In this case a substitution parameter of the form old=new can\nbe  used to modify the command before execution.  For example, with the preset alias r, which\nis aliased to ′hist -s′, typing `r bad=good c' will re-execute the most recent command  which\nstarts  with  the  letter c, replacing the first occurrence of the string bad with the string\ngood.\n"
                },
                {
                    "name": "History Expansion.",
                    "content": "History expansions introduce words from the history list into the  input  stream,  making  it\neasy  to  repeat  commands, repeat arguments of a previous command in the current command, or\nfix typos in the previous command.  The history expansion facility is an alternative to  his‐\ntory control via the fc or hist built-in command.  To enable it, turn on the -H or histexpand\noption using the set command (see Built-in Commands below).\n\nHistory  expansions begin with the character !.  They may begin anywhere in the input.  The !\nmay be preceded by a \\ or enclosed in single quotes to prevent its special meaning.  A  !  is\nalso  passed  unchanged when it is followed by a space, tab, newline, = or (.  History expan‐\nsions do not nest.  They are parsed separately before the shell parser is  invoked,  so  they\ncan override shell grammar rules.\n\nBy  default,  the  expanded version of any line that contains a history expansion is printed,\nadded to the history, and then immediately executed.  History expansions are never  added  to\nthe  history  themselves,  regardless  of whether they succeed or fail due to an error.  Nor‐\nmally, this means that a command line with an erroneous history expansion is lost  and  needs\nto be retyped from scratch, but if the histreedit shell option is turned on and a line editor\nis active (see In-line Editing Options below), the erroneous line is pre-filled into the next\nprompt's  input  buffer for correcting.  The histverify option causes the same to be done for\nthe results of successful history expansions, allowing verification and editing before execu‐\ntion.\n\nA history expansion may have an event specification, which indicates  the  event  from  which\nwords  are  to  be  taken,  a word designator, which selects particular words from the chosen\nevent, and/or a modifier, which manipulates the selected words.\n\nAn event specification can be:\n\nn       A number, referring to a particular event.\n-n      An offset, referring to the event n before the current event.\n#       The current event.\n!       The previous event (equivalent to -1).\ns       The most recent event whose first word begins with the string s.\n?s?     The most recent event which contains the string s.  The second ? can  be  omitted\nif it is immediately followed by a newline.\n\nFor  example,  consider  this bit of someone's history list as might be output by the hist -l\ncommand:\n\n9        nroff -man wumpus.man\n10       cp wumpus.man wumpus.man.old\n11       vi wumpus.man\n12       diff wumpus.man.old wumpus.man\n\nThe commands are shown with their event numbers.  The current event, which we  haven't  typed\nin  yet,  is  event 13.  !11 and !-2 refer to event 11.  !! refers to the previous event, 12.\n!! can be abbreviated ! if it is followed by : (see below).  !n refers to event 9, which  be‐\ngins  with  n.  !?old? also refers to event 12, which contains old.  Without word designators\nor modifiers, history references simply expand to the entire event, so we might type  !cp  to\nredo the copy command or !!|more if the diff output scrolled off the top of the screen.\n\nTo  select words from an event, the event specification can be followed by a : and a designa‐\ntor for the desired words.  The words of an input line are numbered from 0,  the  first  word\n(usually the command name) being 0, the second word (first argument) being 1, etc.  The basic\nword designators are:\n\n0       The first word (command name).\nn       The nth argument.\n^       The first argument, equivalent to 1.\n$       The last argument.\n%       The word matched by the most recent ?s? search.\nx-y     A range of words.\n-y      Equivalent to 0-y.\n*       Equivalent to ^-$, but returns nothing if the event contains only 1 word.\nx*      Equivalent to x-$.\nx-      Equivalent to x*, but omitting the last word ($).\n\nSelected  words  are inserted into the command line separated by single blanks.  For example,\nthe diff command in the previous example might have been typed as diff !!:1.old  !!:1  (using\n:1  to  select  the first argument from the previous event) or diff !-2:2 !-2:1 to select and\nswap the arguments from the cp command.  If we didn't care about the order of  the  diff,  we\nmight have said diff !-2:1-2 or simply diff !-2:*.  The cp command might have been written cp\nwumpus.man  !#:1.old, using # to refer to the current event.  !n:- hurkle.man would reuse the\nfirst two words from the nroff command to say nroff -man hurkle.man.\n\nThe : separating the event specification from the word designator can be omitted if the argu‐\nment selector begins with a ^, $, *, % or -.  For example, our diff command might  have  been\ndiff !!^.old !!^ or, equivalently, diff !!$.old !!$.  However, if !! is abbreviated !, an ar‐\ngument selector beginning with - will be interpreted as an event specification.\n\nThe  word(s)  in  a  history reference can be edited by following them with one or more modi‐\nfiers, each preceded by a colon (:):\n\nh       Remove a trailing pathname component, leaving the head.\nt       Remove all leading pathname components, leaving the tail.\nr       Remove a filename extension .xxx, leaving the root name.\ne       Remove all but the extension.\ns/l/r/  Substitute l for r.  l is simply a string like r, not a regular expression as  in\nthe eponymous ed(1) command.  Any character may be used as the delimiter in place\nof  /; a \\ can be used to quote the delimiter inside l and r.  The character & in\nthe r is replaced by l; \\ also quotes &.  If l is empty, the l from the  previous\nsubstitution is used, or if there is none, the s from the most recent ?s? search.\nThe trailing delimiter may be omitted if it is immediately followed by a newline.\n&       Repeat the previous substitution.\ng       Global  substitution,  for example :gs/foo/bar/ or :g&.  Applies the s or & modi‐\nfier to the entire command line.\na       Same as g.\np       Print the new command line but do not execute it.\nq       Quote the expanded words, preventing further expansions.\nx       Like q, but break into words at blanks, tabs and newlines.\n\nModifiers are applied to only the first modifiable word (unless g or a is used).   It  is  an\nerror for no word to be modifiable.\n\nFor  example, the diff command might have been written as diff wumpus.man.old !#^:r, using :r\nto remove .old from the first argument on the same line (!#^).  We might follow  mail  -s  \"I\nforgot my password\" rot with !:s/rot/root to correct the spelling of root.\n\nHistory expansions also occur when an input line begins with ^.  When it is the first charac‐\nter  on  an  input line, it is an abbreviation of !:s^.  Thus we might have said ^rot^root to\nmake the spelling correction in the previous example.  This is  the  only  history  expansion\nthat does not explicitly begin with !.\n\nIf a word on a command line begins with the history comment character #, history expansion is\nignored for the rest of that line.  This usually causes the shell parser (which uses the same\ncharacter  to  signal  a  comment) to treat the rest of the line as a comment as well, but as\nhistory expansion is parsed separately from the shell grammar and with different rules,  this\ncannot  be  guaranteed  in all cases.  If the history comment character is changed, the shell\ngrammar comment character does not change along with it.\n\nThe three characters used to signal history expansion can  be  changed  using  the  histchars\nshell variable; see Shell Variables above.\n"
                },
                {
                    "name": "In-line Editing Options.",
                    "content": "Normally, each command line entered from a terminal device is simply typed followed by a new-\nline (`RETURN' or `LINE FEED').  If either the emacs, gmacs, or vi option is active, the user\ncan  edit  the  command line.  To be in either of these edit modes, set the corresponding op‐\ntion.  An editing option is automatically selected each time the VISUAL or EDITOR variable is\nassigned a value matching any of these editor names; for details, see Shell  Variables  above\nunder VISUAL.\n\nThe  editing  features  require  that  the user's terminal accept `RETURN' as carriage return\nwithout line feed and that a space (` ') must overwrite the current character on the screen.\n\nUnless the multiline option is on, the editing modes implement a concept where  the  user  is\nlooking through a window at the current line.  The window width is the value of COLUMNS if it\nis  defined,  otherwise 80.  If the window width is too small to display the prompt and leave\nat least 8 columns to enter input, the prompt is truncated from the left.   If  the  line  is\nlonger  than  the window width minus two, a mark is displayed at the end of the window to no‐\ntify the user.  As the cursor moves and reaches the window boundaries,  the  window  will  be\ncentered  about  the  cursor.  The mark is a > (<, *) if the line extends on the right (left,\nboth) side(s) of the window.\n\nThe search commands in each edit mode provide access to the history file.  Only  strings  are\nmatched, not patterns, although a leading ^ in the string restricts the match to begin at the\nfirst character in the line.\n\nEach  of the edit modes has an operation to list the files or commands that match a partially\nentered word.  When applied to the first word on the line, or the first word after a ;, |, &,\nor (, and the word does not begin with ∼ or contain a /, the list of aliases, functions,  and\nexecutable  commands  defined  by the PATH variable that could match the partial word is dis‐\nplayed.  Otherwise, the list of files that match the given word is displayed.   If  the  par‐\ntially  entered  word  does not contain any file expansion characters, a * is appended before\ngenerating these lists.  After displaying the generated list,  the  input  line  is  redrawn.\nThese  operations are called command name listing and file name listing, respectively.  There\nare additional operations, referred to as command name completion and file  name  completion,\nwhich  compute  the list of matching commands or files, but instead of printing the list, re‐\nplace the current word with a complete or partial match.  For file name  completion,  if  the\nmatch  is  unique,  a / is appended if the file is a directory and a space is appended if the\nfile is not a directory.  Otherwise, the longest common prefix for all the matching files re‐\nplaces the word.  For command name completion, only the portion of the file names  after  the\nlast  / are used to find the longest command prefix.  If only a single name matches this pre‐\nfix, then the word is replaced with the command name followed by a space.  When using  a  tab\nfor  completion  that does not yield a unique match, a subsequent tab will provide a numbered\nlist of matching alternatives.  A specific selection can be made by  entering  the  selection\nnumber followed by a tab.  Neither completion nor listing operations are attempted before the\nfirst character in a line.\n"
                },
                {
                    "name": "Key Bindings.",
                    "content": "The KEYBD trap can be used to intercept keys as they are typed and change the characters that\nare  actually  seen by the shell.  This trap is executed after each character (or sequence of\ncharacters when the first character is ESC) is entered while reading from  a  terminal.   The\nvariable  .sh.edchar  contains  the character or character sequence which generated the trap.\nChanging the value of .sh.edchar in the trap action causes the shell to behave as if the  new\nvalue were entered from the keyboard rather than the original value.\n\nThe variable .sh.edcol is set to the input column number of the cursor at the time of the in‐\nput.   The variable .sh.edmode is set to ESC when in vi input mode (see below) and set to the\nempty string otherwise.  Prepending ${.sh.editmode} to a value assigned  to  .sh.edchar  will\ncause the shell to change to control mode if it is not already in this mode.\n\nThis  trap is not invoked for characters entered as arguments to editing directives, or while\nreading input for a character search.\n"
                },
                {
                    "name": "Emacs Editing Mode.",
                    "content": "This mode is entered by enabling either the emacs or gmacs option.  The only  difference  be‐\ntween  these  two modes is the way they handle ^T.  To edit, the user moves the cursor to the\npoint needing correction and then inserts or deletes characters or words as needed.  All  the\nediting  commands are control characters or escape sequences.  The notation for control char‐\nacters is caret (^) followed by the character.  For example, ^F is the notation  for  control\nF.   This  is  entered  by  depressing  `f' while holding down the `CTRL' (control) key.  The\n`SHIFT' key is not depressed.  (The notation ^?  indicates the DEL (delete) key.)\n\nThe notation for escape sequences is M- followed by a  character.   For  example,  M-f  (pro‐\nnounced  Meta f) is entered by depressing ESC (ASCII 033) followed by `f'.  (M-F would be the\nnotation for ESC followed by `SHIFT' (capital) `F'.)\n\nAll edit commands operate from any place on the line (not just at  the  beginning).   Neither\nthe `RETURN' nor the `LINE FEED' key is entered after edit commands except when noted.\n\nThe  M-[  multi-character  commands below are DEC VT220 escape sequences generated by special\nkeys on standard PC keyboards, such as the arrow keys.  You could type them directly but they\nare meant to recognize the keys in question, which are indicated in parentheses.\n\n^F        Move cursor forward (right) one character.\nM-[C      (Right arrow) Same as ^F.\nM-f       Move cursor forward one word.  (The emacs editor's idea of a word is  a  string  of\ncharacters consisting of only letters, digits and underscores.)\nM-[1;3C   (Alt-Right arrow) Same as M-f.\nM-[1;5C   (Ctrl-Right arrow) Same as M-f.\nM-[1;9C   (iTerm2 Alt-Right arrow) Same as M-f.\n^B        Move cursor backward (left) one character.\nM-[D      (Left arrow) Same as ^B.\nM-b       Move cursor backward one word.\nM-[1;3D   (Alt-Left arrow) Same as M-b.\nM-[1;5D   (Ctrl-Left arrow) Same as M-b.\nM-[1;9D   (iTerm2 Alt-Left arrow) Same as M-b.\n^A        Move cursor to start of line.\nM-[H      (Home) Same as ^A.\nM-[1~     Same as ^A.\nM-[7~     Same as ^A.\n^E        Move cursor to end of line.\nM-[F      (End) Same as ^E.\nM-[4~     Same as ^E.\nM-[8~     Same as ^E.\nM-[Y      Same as ^E.\nM-OA      (Up Arrow) Same as M-[A.\nM-OB      (Down Arrow) Same as M-[B.\nM-OC      (Right Arrow) Same as M-[C.\nM-OD      (Left Arrow) Same as M-[D.\nM-O5C     (Ctrl-Right Arrow) Same as M-f.\nM-O5D     (Ctrl-Left Arrow) Same as M-b.\n^]char    Move cursor forward to character char on current line.\nM-^]char  Move cursor backward to character char on current line.\n^X^X      Interchange the cursor and mark.\nerase     (User  defined  erase  character  as  defined  by the stty(1) command, usually ^H.)\nDelete previous character.\nlnext     (User defined literal next character as defined by the stty(1) command,  or  ^V  if\nnot defined.)  Removes the next character's editing features (if any).\n^D        Delete current character.\nM-[3~     (Forward delete) Same as ^D.\nM-d       Delete current word.\nM-[3;5~   (Ctrl-Delete) Same as M-d.\nM-^H      (Meta-backspace) Delete previous word.\nM-h       Delete previous word.\nM-^?      (Meta-DEL)  Delete  previous word (if your interrupt character is ^?  (DEL, the de‐\nfault) then this command will not work).\n^T        Transpose current character with previous character and advance the cursor in emacs\nmode.  Transpose two previous characters in gmacs mode.\n^C        Capitalize current character.\nM-c       Capitalize current word.\nM-l       Change the current word to lower case.\n^K        Delete from the cursor to the end of the line.  If preceded by a numerical  parame‐\nter  whose  value  is less than the current cursor position, then delete from given\nposition up to the cursor.  If preceded by a numerical  parameter  whose  value  is\ngreater  than the current cursor position, then delete from cursor up to given cur‐\nsor position.\n^W        Kill from the cursor to the mark.\nM-p       Push the region from the cursor to the mark on the stack.\nkill      (User defined kill character as defined by the stty(1) command, usually ^U.)   Kill\nthe  entire  current  line.   If two kill characters are entered in succession, all\nkill characters from then on cause a line feed (useful when using paper terminals).\nA subsequent pair of kill characters undoes this change.\n^Y        Restore last item removed from line. (Yank item back to the line.)\n^X^E      Return the command hist -e ${VISUAL:-${EDITOR:-vi}} in the input buffer to  call  a\nfull editor — vi by default — on the current command line.\n^L        Line feed and print current line.\nM-^L      Clear the screen.\n^@        (Null character) Set mark.\nM-space   (Meta space) Set mark.\n^J        (New line) Execute the current line.\n^M        (Return) Execute the current line.\neof       End-of-file character, normally ^D, is processed as an End-of-file only if the cur‐\nrent line is empty.\n^P        Fetch  previous command.  Each time ^P is entered the previous command back in time\nis accessed.  Moves back one line when not on the first line of a  multi-line  com‐\nmand.\nM-[A      (Up  arrow)  If  the  cursor is at the end of the line, it is equivalent to ^R with\nstring set to the contents of the current line.  Otherwise, it is equivalent to ^P.\nM-<       Fetch the least recent (oldest) history line.\nM->       Fetch the most recent (youngest) history line.\n^N        Fetch next command line.  Each time ^N is entered the next command line forward  in\ntime is accessed.\nM-[B      (Down arrow) Equivalent to ^N.\n^Rstring  Reverse search history for a previous command line containing string.  If a parame‐\nter of zero is given, the search is forward.  String is terminated by a `RETURN' or\n`NEW LINE'.  If string is preceded by a ^, the matched line must begin with string.\nIf  string is omitted, then the next command line containing the most recent string\nis accessed.  In this case a parameter  of  zero  reverses  the  direction  of  the\nsearch.\n^G        Exit reverse search mode.\n^O        Operate - Execute the current line and fetch the next line relative to current line\nfrom the history file.\nM-digits  (Escape)  Define numeric parameter, the digits are taken as a parameter to the next\ncommand.  The commands that accept a parameter are ^F, ^B, erase, ^C, ^D,  ^K,  ^R,\n^P,  ^N, ^], M-., M-^], M-, M-=, M-b, M-c, M-d, M-f, M-h, M-l, M-^H, and the arrow\nkeys and forward-delete key.\nM-letter  Soft-key - Your alias list is searched for an alias by the name letter and  if  an\nalias  of this name is defined, its value will be inserted on the input queue.  The\nletter must not be one of the above meta-functions.\nM-[letter Soft-key - Your alias list is searched for an alias by the name letter and if  an\nalias of this name is defined, its value will be inserted on the input queue.  This\ncan be used to program function keys on many terminals.\nM-.       The  last  word  of the previous command is inserted on the line.  If preceded by a\nnumeric parameter, the value of this parameter  determines  which  word  to  insert\nrather than the last word.\nM-       Same as M-..\nM-*       Attempt  pathname  expansion  on  the current word.  An asterisk is appended if the\nword doesn't match any file or contain any special pattern characters.\nM-ESC     Command or file name completion as described above.\n^I tab    Attempts command or file name completion as described above.  If a partial  comple‐\ntion  occurs,  repeating  this  will behave as if M-= were entered.  If no match is\nfound or entered after space, a tab is inserted.\nM-=       If not preceded by a numeric parameter, it generates the list of matching  commands\nor file names as described above.  Otherwise, the word under the cursor is replaced\nby  the  item corresponding to the value of the numeric parameter from the most re‐\ncently generated command or file list.  If the cursor is not on a word, it  is  in‐\nserted instead.\n^U        Multiply parameter of next command by 4.\n\\         If  the  backslashctrl  shell option is on (which is the default setting), this es‐\ncapes the next character.  Editing characters, the user's erase, kill and interrupt\n(normally ^C) characters may be entered in a command line or in a search string  if\npreceded  by  a  \\.   The \\ removes the next character's editing features (if any).\nSee also lnext which is not subject to any shell option.\nM-^V      Display version of the shell.\nM-[2~     (Insert) Escape the next character.\nM-#       If the line does not begin with a #, a # is inserted at the beginning of  the  line\nand  after each new-line, and the line is entered.  This causes a comment to be in‐\nserted in the history file.  If the line begins with a #, the # is deleted and  one\n# after each new-line is also deleted.\n"
                },
                {
                    "name": "Vi Editing Mode.",
                    "content": "There  are  two typing modes.  Initially, when you enter a command you are in the input mode.\nTo edit, the user enters control mode by typing ESC (033) and moves the cursor to  the  point\nneeding  correction  and then inserts or deletes characters or words as needed.  Most control\ncommands accept an optional repeat count prior to the command.\n\nThe notation for control characters used below is ^ followed by a character. For instance, ^H\nis entered by holding down the Control key and pressing H.  ^[ (Control+[) is  equivalent  to\nthe ESC key.  The notation for escape sequences is ^[ followed by one or more characters.\n\nThe  ^[[  (ESC  [) multi-character commands below are DEC VT220 escape sequences generated by\nspecial keys on standard PC keyboards, such as the arrow keys, which are indicated in  paren‐\ntheses.  When in input mode, these keys will switch you to control mode before performing the\nassociated action.  These sequences can use preceding repeat count parameters, but only  when\nthe  ^[ and the subsequent [ are entered into the input buffer at the same time, such as when\npressing one of those keys.\n"
                },
                {
                    "name": "Input Edit Commands",
                    "content": "By default the editor is in input mode.\n\nerase     (User defined erase character as defined by the stty(1) command, usually  ^H\nor #.)  Delete previous character.\n^W        Delete the previous blank separated word.\neof       As  the first character of the line causes the shell to terminate unless the\nignoreeof option is set.  Otherwise this character is ignored.\nlnext     (User defined literal next character as defined by the stty(1) or ^V if  not\ndefined.)  Removes the next character's editing features (if any).\n\\         If the backslashctrl shell option is on (which is the default setting), this\nescapes the next erase or kill character.\n^I tab    Attempts  command  or file name completion as described above and returns to\ninput mode. If a partial completion occurs, repeating this will behave as if\n= were entered from control mode.  If no match is  found  or  entered  after\nspace, a tab is inserted.\n"
                },
                {
                    "name": "Motion Edit Commands",
                    "content": "These commands will move the cursor.\n\n[count]l  Cursor forward (right) one character.\n[count]^[[C\n(Right arrow) Same as l.\n[count]w  Cursor forward one alphanumeric word.\n[count]W  Cursor to the beginning of the next word that follows a blank.\n[count]e  Cursor to end of word.\n[count]E  Cursor to end of the current blank delimited word.\n[count]h  Cursor backward (left) one character.\n[count]^[[D\n(Left arrow) Same as h.\n[count]b  Cursor backward one word.\n[count]B  Cursor to preceding blank separated word.\n[count]|  Cursor to column count.\n[count]fc Find the next character c in the current line.\n[count]Fc Find the previous character c in the current line.\n[count]tc Equivalent to f followed by h.\n[count]Tc Equivalent to F followed by l.\n[count];  Repeats count times, the last single character find command, f, F, t, or T.\n[count],  Reverses the last single character find command count times.\n0         Cursor to start of line.\n^[[H      (Home) Same as 0.\n^[[1~     Same as 0.\n^[[7~     Same as 0.\n^[[1;3D   (Alt-Left arrow) Same as b.\n^[[1;5D   (Ctrl-Left arrow) Same as b.\n^[[1;9D   (iTerm2 Alt-Left arrow) Same as b.\n^[[1;3C   (Alt-Right arrow) Same as w.\n^[[1;5C   (Ctrl-Right arrow) Same as w.\n^[[1;9C   (iTerm2 Alt-Right arrow) Same as w.\n^[[2~     (Insert) Same as i.\n^[[3;5~   (Ctrl-Delete) Same as dw.\n^[OA      (Up Arrow) Same as ^[[A.\n^[OB      (Down Arrow) Same as ^[[B.\n^[OC      (Right Arrow) Same as ^[[C.\n^[OD      (Left Arrow) Same as ^[[D.\n^[O5C     (Ctrl-Right Arrow) Same as w.\n^[O5D     (Ctrl-Left Arrow) Same as b.\n^         Cursor to first non-blank character in line.\n$         Cursor to end of line.\n^[[F      (End) Same as $.\n^[[4~     Same as $.\n^[[8~     Same as $.\n^[[Y      Same as $.\n^G        Exit reverse search mode.\n%         Moves  to  balancing  (,  ),  {, }, [, or ].  If cursor is not on one of the\nabove characters, the remainder of the line is searched for the first occur‐\nrence of one of the above characters first.\n"
                },
                {
                    "name": "Search Edit Commands",
                    "content": "These commands access your command history.\n\n[count]k  Fetch previous command.  Each time k is entered the previous command back in\ntime is accessed.\n[count]-  Equivalent to k.\n[count]^[[A\n(Up arrow) If cursor is at the end of the line it is equivalent  to  /  with\nstring set to the contents of the current line.  Otherwise, it is equivalent\nto k.\n[count]j  Fetch next command.  Each time j is entered the next command forward in time\nis accessed.\n[count]+  Equivalent to j.\n[count]^[[B\n(Down arrow) Equivalent to j.\n[count]G  The  command  number count is fetched.  The default is the least recent his‐\ntory command.\n/string   Search backward through history for a previous  command  containing  string.\nString  is terminated by a `RETURN' or `NEW LINE'.  If string is preceded by\na ^, the matched line must begin with string.  If string is empty, the  pre‐\nvious string will be used.\n?string   Same as / except that search will be in the forward direction.\nn         Search for next match of the last pattern to / or ?  commands.\nN         Search  for  next match of the last pattern to / or ?, but in reverse direc‐\ntion.\n"
                },
                {
                    "name": "Text Modification Edit Commands",
                    "content": "These commands will modify the line.\n\na         Enter input mode and enter text after the current character.\nA         Append text to the end of the line.  Equivalent to $a.\n[count]cmotion\nc[count]motion\nDelete current character through the character that motion  would  move  the\ncursor  to  and  enter  input mode.  If motion is c, the entire line will be\ndeleted and input mode entered.\nC         Delete the current character through the end of line and enter  input  mode.\nEquivalent to c$.\nS         Equivalent to cc.\n[count]s  Replace characters under the cursor in input mode.\nD         Delete the current character through the end of line.  Equivalent to d$.\n[count]dmotion\nd[count]motion\nDelete  current  character  through the character that motion would move to.\nIf motion is d , the entire line will be deleted.\ni         Enter input mode and insert text before the current character.\nI         Insert text before the first non-blank character.  Equivalent to ^i.\n[count]P  Place the previous text modification before the cursor.\n[count]p  Place the previous text modification after the cursor.\nR         Enter input mode and replace characters on the screen  with  characters  you\ntype overlay fashion.\n[count]rc Replace  the count character(s) starting at the current cursor position with\nc, and advance the cursor.\n[count]x  Delete current character.\n[count]^[[3~\n(Forward delete) Same as x.\n[count]X  Delete preceding character.\n[count].  Repeat the previous text modification command.\n[count]∼  Invert the case of the count character(s) starting at the current cursor po‐\nsition and advance the cursor.\n[count]  Causes the count word of the previous command to be appended and input  mode\nentered.  The last word is used if count is omitted.\n*         Causes  an  *  to be appended to the current word and pathname expansion at‐\ntempted.  If no match is found, it rings the bell.  Otherwise, the  word  is\nreplaced by the matching pattern and input mode is entered.\n\\         Command or file name completion as described above.\n"
                },
                {
                    "name": "Other Edit Commands",
                    "content": "Miscellaneous commands.\n\n[count]ymotion\ny[count]motion\nYank  current  character through character that motion would move the cursor\nto and puts them into the delete buffer.  The text and cursor are unchanged.\nyy        Yanks the entire line.\nY         Yanks from current position to end of line.  Equivalent to y$.\nu         Undo the last text modifying command.\nU         Undo all the text modifying commands performed on the line.\n[count]v  Returns the command hist -e  ${VISUAL:-${EDITOR:-vi}}  count  in  the  input\nbuffer to call a full editor — vi by default — on a history entry.  If count\nis omitted, then the current line is used.\n^L        Line feed and print current line.  Has effect only in control mode.\n^J        (New line) Execute the current line, regardless of mode.\n^M        (Return) Execute the current line, regardless of mode.\n#         If the first character of the command is a #, then this command deletes this\n#  and  each  # that follows a newline.  Otherwise, sends the line after in‐\nserting a # in front of each line in the command.  Useful  for  causing  the\ncurrent  line  to  be  inserted in the history as a comment and uncommenting\npreviously commented commands in the history file.\n[count]=  If count is not specified, it generates the list  of  matching  commands  or\nfile  names as described above.  Otherwise, the word under the cursor is re‐\nplaced by the count item from the most recently generated  command  or  file\nlist.  If the cursor is not on a word, it is inserted instead.\n@letter   Your alias list is searched for an alias by the name letter and if an alias\nof  this  name is defined, its value will be inserted on the input queue for\nprocessing.\n^V        Display version of the shell.\n"
                },
                {
                    "name": "Built-in Commands.",
                    "content": "The simple-commands listed below are built in to the shell  and  are  executed  in  the  same\nprocess  as  the  shell.  The effects of any added Input/Output redirections are local to the\ncommand, except for the exec and redirect commands.  Unless otherwise indicated,  the  output\nis  written on standard output (file descriptor 1) and the exit status, when there is no syn‐\ntax error, is zero.  Except for :, true, false, and echo, all built-in commands accept --  to\nindicate end of options, and are self-documenting.\n\nThe  self-documenting  commands  interpret the option --man as a request to display that com‐\nmand's own manual page, --help as a request to display the OPTIONS section from their  manual\npage,  and -?  as a request to print a brief usage message.  All these are processed as error\nmessages, so they are written on standard error (file descriptor 2) and to pipe them  into  a\npager  such  as more(1) you need to add a 2>&1 redirection before the |. The display of bold‐\nface text depends on whether standard error is on a terminal, so is  disabled  when  using  a\npager. Exporting the ERROROPTIONS environment variable with a value containing emphasis will\nforce  this on; a value containing noemphasis forces it off.  The test/[ command needs an ad‐\nditional -- argument to recognize self-documentation options, e.g. test --man --.   The  exec\nand redirect commands, as they make redirections permanent, should use self-documentation op‐\ntions in a subshell when redirecting, for example: (redirect --man) 2>&1.  There are advanced\noutput options as well; see getopts --man for more information.\n\nCommands  that are preceded by a † symbol below are special built-in commands and are treated\nspecially in the following ways:\n1.     Variable assignment lists preceding the command remain in effect when the  com‐\nmand completes.\n2.     I/O redirections are processed after variable assignments.\n3.     Errors cause a script that contains them to abort.\n4.     They are not valid function names.\n\nCommands that are preceded by a ‡ symbol below are declaration commands.  Any following words\nthat  are  in the format of a variable assignment are expanded with the same rules as a vari‐\nable assignment.  This means that tilde expansion is performed after the =  sign,  array  as‐\nsignments  of  the form varname=(assignlist) are supported, and field splitting and pathname\nexpansion are not performed.\n\n† : [ arg ... ]\nThe command only expands parameters.\n\n† . name [ arg ... ]\nIf name is a function defined with the function name reserved word syntax,  the  func‐\ntion is executed in the current environment (as if it had been defined with the name()\nsyntax).  Otherwise if name refers to a file, the file is read in its entirety and the\ncommands  are executed in the current shell environment.  The search path specified by\nPATH is used to find the directory containing the file.   If  any  arguments  arg  are\ngiven,  they  become the positional parameters while processing the .  command and the\noriginal positional parameters are restored upon completion.  Otherwise the positional\nparameters are unchanged.  The exit status is the exit status of the last command exe‐\ncuted.\n\n[ expression ]\nThe [ command is the same as test, with the exception that an additional closing ] ar‐\ngument is required. See test below.\n\nalias [ -ptx ]  [ name[ =value  ] ] ...\nalias with no arguments prints the list of aliases in the form name=value on  standard\noutput.  The -p option causes the word alias to be inserted before each one.  When one\nor  more  arguments are given, an alias is defined for each name whose value is given.\nA trailing space in value causes the next word to be checked for  alias  substitution.\nWith the -t option, each name is looked up as a command in $PATH and its path is added\nto the hash table as a 'tracked alias'.  If no name is given, this prints the hash ta‐\nble. See hash.  Without the -t option, for each name in the argument list for which no\nvalue  is  given,  the name and value of the alias is printed.  The obsolete -x option\nhas no effect in most contexts, although if it's used with -t  it  will  suppress  all\noutput.   The  exit  status is non-zero if a name is given, but no value, and no alias\nhas been defined for the name.\n\nautoload name ...\nMarks each name undefined so that the FPATH variable will  be  searched  to  find  the\nfunction definition when the function is referenced.  The same as typeset -fu.\n\nbg [ job... ]\nThis  command  is  only  on systems that support job control.  Puts each specified job\ninto the background.  The current job is put in the background if job  is  not  speci‐\nfied.  See Jobs for a description of the format of job.\n\n† break [ n ]\nExit from the enclosing for, while, until, or select loop, if any.  If n is specified,\nthen break n levels.\n\nbuiltin [ -ds ] [ -f file ] [ name ... ]\nIf  name is not specified, and no -f option is specified, the built-ins are printed on\nstandard output.  The -s option prints only the special  built-ins.   Otherwise,  each\nname  represents  the  pathname whose basename is the name of the built-in.  The entry\npoint function name is determined by prepending b to the built-in name.   A  built-in\nspecified by a pathname will only be executed when that pathname would be found during\nthe  path  search.  Built-ins found in libraries loaded via the .paths file will asso‐\nciate with the pathname of the directory containing the .paths file.\n\nThe ISO C/C++ prototype is bmycommand(int argc, char *argv[], void *context) for  the\nbuiltin  command  mycommand  where argv is array an of argc elements and context is an\noptional pointer to a Shellt structure as described in <ast/shell.h>.\n\nSpecial built-ins cannot be bound to a pathname or deleted.   The  -d  option  deletes\neach  of  the given built-ins.  On systems that support dynamic loading, the -f option\nnames a shared library containing the code for built-ins.  The shared  library  prefix\nand/or  suffix, which depend on the system, can be omitted.  Once a library is loaded,\nits symbols become available for subsequent  invocations  of  builtin.   Multiple  li‐\nbraries  can be specified with separate invocations of the builtin command.  Libraries\nare searched in the reverse order in which they are  specified.   When  a  library  is\nloaded,  it  looks  for a function in the library whose name is libinit() and invokes\nthis function with an argument of 0.\n\ncd [ -L ] [ -eP ] [ arg ]\ncd [ -L ] [ -eP ] old new\nThis command can be in either of two forms.  In the first form it changes the  current\ndirectory  to  arg.   If  arg is - the directory is changed to the previous directory.\nThe shell variable HOME is the default arg.  The variable PWD is set  to  the  current\ndirectory.   The  shell variable CDPATH defines the search path for the directory con‐\ntaining arg.  Alternative directory names are separated by a colon (:).   The  default\npath  is  the  empty string (specifying the current directory).  Note that the current\ndirectory may be specified by a dot (.)  or by an empty path name, either of which can\nappear immediately after the equal sign or between the colon delimiters anywhere  else\nin  the  path  list.  If arg begins with a / then the search path is not used.  Other‐\nwise, each directory in the path is searched for arg.\nThe second form of cd substitutes the string new for the string old in the current di‐\nrectory name, PWD, and tries to change to this new directory.\nBy default, symbolic link names are treated literally when finding the directory name.\nThis is equivalent to the -L option.  The -P option causes symbolic links  to  be  re‐\nsolved  when  determining the directory.  The last instance of -L or -P on the command\nline determines which method is used.\nIf -e and -P are both in effect and the correct PWD could not be determined after suc‐\ncessfully changing the directory, cd will return with exit status one and  produce  no\noutput.   If  any  other  error occurs while both flags are active, the exit status is\ngreater than one.\nThe cd command may not be executed by rksh.\n\ncommand [ -pvxV ] name [ arg ... ]\nWith the -v option, command is equivalent to the built-in whence command described be‐\nlow.  The -V option causes command to act like whence -v.\n\nWithout the -v or -V options, command executes name with the arguments given  by  arg.\nFunctions and aliases will not be searched for when finding name.  If name refers to a\nspecial  built-in, as marked with † in this manual, command disables the special prop‐\nerties described above for that mark, executing the command  as  a  regular  built-in.\n(For example, using command set -o option-name prevents a script from terminating when\nan invalid option name is given.)\n\nThe -p option causes the operating system's standard utilities path (as output by get‐\nconf PATH) to be searched rather than the one defined by the value of PATH.\n\nThe  -x  option searches for name as an external command, bypassing built-ins.  If the\narguments contain at least one word that expands to multiple  arguments,  for  example\n*.txt  or  \"$@\", then the -x option also allows executing external commands with argu‐\nment lists that are longer than the operating system  allows.  This  functionality  is\nsimilar to xargs(1) but is easier to use. The shell does this by invoking the external\ncommand multiple times if needed, dividing the expanded argument list over the invoca‐\ntions.  Any  arguments  that come before the first word that expands to multiple argu‐\nments, as well as any that follow the last such word, are repeated  for  each  invoca‐\ntion. This allows each invocation to use the same command options, as well as the same\ntrailing destination arguments for commands like cp(1) or mv(1).  When all invocations\nare completed, command -x exits with the status of the invocation that had the highest\nexit  status.   (Note  that command -x may still fail with an \"argument list too long\"\nerror if a single argument exceeds the maximum length of the argument list,  or  if  a\nlong arguments list contains no word that expands to multiple arguments.)\n\n‡ compound vname[=value] ...\nCauses each vname to be a compound variable.  The same as typeset -C.\n\n† continue [ n ]\nResume the next iteration of the enclosing for, while, until, or select loop.  If n is\nspecified, then resume at the n-th enclosing loop.\n\ndisown [ job... ]\nCauses the shell not to send a HUP signal to each given job, or all active jobs if job\nis omitted, when a login shell terminates.\n\necho [ arg ... ]\nWhen  the  first  arg  does not begin with a -, and none of the arguments contain a \\,\nthen echo prints each of its arguments separated by a space and terminated by  a  new-\nline.   Otherwise,  the  behavior  of echo is system dependent and print or printf de‐\nscribed below should be used.  See echo(1) for usage and description.\n\n‡ enum [ -i ] type[=(value ...) ] ...\nCreates, for each type specified, an enumeration type declaration command named  type.\nVariables  of  the created type can only store any one of the values given.  For exam‐\nple, enum bool=(false true) creates a Boolean variable type of which variables may  be\ndeclared  like  bool x=true y=false.  If =(value ...) is omitted, then type must be an\nindexed array variable with at least two elements and the values are taken  from  this\narray variable.  If -i is specified the values are case-insensitive.  Declaration com‐\nmands  are  created  as special builtins that cannot be removed or overridden by shell\nfunctions.  Each created declaration command has a --man option that shows  documenta‐\ntion on its type's behavior and possible values.\n\nWithin arithmetic expressions (see Arithmetic Evaluation above), enumeration type val‐\nues  translate to index numbers between 0 and the number of defined values minus 1. It\nis an error for an arithmetic expression to assign a value outside of that range. Dec‐\nimal fractions are ignored.  Taking the bool type from the example above, if  a  vari‐\nable  of this type is used in an arithmetic expression, false translates to 0 and true\nto 1.  Enumeration values may also be used directly in an arithmetic  expression  that\nrefers  to  a  variable  of  an enumeration type.  To continue our example, for a bool\nvariable v, ((v==true)) is the same as ((v==1)) and if a variable named  true  exists,\nit is ignored.\n\n† eval [ arg ... ]\nThe arguments are read as input to the shell and the resulting command(s) executed.\n\n† exec [ -c ] [ -a name ] [ arg ... ]\nIf  arg  is given, the command specified by the arguments is executed in place of this\nshell without creating a new process.  The value of the SHLVL environment variable  is\ndecreased  by  one, unless the shell replaced is a subshell.  The -c option causes the\nenvironment to be cleared before applying variable  assignments  associated  with  the\nexec  invocation.   The  -a  option  causes  name rather than the first arg, to become\nargv[0] for the new process.  If arg is not given and only I/O redirections are given,\nthen this command persistently modifies file descriptors as in redirect.\n\n† exit [ n ]\nCauses the shell to exit with the exit status specified by n.  The value will  be  the\nleast significant 8 bits of n (if specified) or of the exit status of the last command\nexecuted.  An end-of-file will also cause the shell to exit, except for an interactive\nshell that has the ignoreeof option turned on (see set below).\n\n†‡ export [ -p ] [ name[=value] ] ...\nIf  name is not given, the names and values of each variable with the export attribute\nare printed with the values quoted in a manner that allows them to be  re-input.   The\nexport  command is the same as typeset -x except that if you use export within a func‐\ntion, no local variable is created.  The -p option causes the word export  to  be  in‐\nserted before each one.  Otherwise, the given names are marked for automatic export to\nthe environment of subsequently-executed commands.\n\nfalse  Does nothing, and exits 1. Used with until for infinite loops.\n\nfc [ -e ename  ] [ -N num ] [ -nlr ] [ first [ last ] ]\nfc -s  [ old=new ] [ command ]\nThe same as hist.\n\nfg [ job... ]\nThis  command  is  only  on  systems  that support job control.  Each job specified is\nbrought to the foreground and waited for in the specified order.  Otherwise, the  cur‐\nrent  job is brought into the foreground.  See Jobs for a description of the format of\njob.\n\n‡ float vname[=value] ...\nDeclares each vname to be a long floating point number.  The same as typeset -lE.\n\nfunctions [ -Stux ] [ name ... ]\nLists functions.  The same as typeset -f.\n\ngetconf [ name [ pathname ] ]\nPrints the current value of the configuration parameter given by name.  The configura‐\ntion parameters are defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2  standards.\n(See  pathconf(2)  and  sysconf(3).)  The pathname argument is required for parameters\nwhose value depends on the location in the file system.  If no  arguments  are  given,\ngetconf  prints  the  names  and  values of the current configuration parameters.  The\npathname / is used for each of the parameters that requires pathname.\n\ngetopts [ -a name ] optstring vname [ arg ... ]\nChecks arg for legal options.  If arg is omitted, the positional parameters are  used.\nAn option argument begins with a + or a -.  An option not beginning with + or - or the\nargument  -- ends the options.  Options beginning with + are only recognized when opt‐\nstring begins with a +.  optstring contains the letters that getopts recognizes.  If a\nletter is followed by a :, that option is expected to have an argument.   The  options\ncan be separated from the argument by blanks.  The option -?  causes getopts to gener‐\nate  a  usage  message  on standard error.  The -a argument can be used to specify the\nname to use for the usage message, which defaults to $0.\ngetopts places the next option letter it finds inside variable vname each time  it  is\ninvoked.   The option letter will be prepended with a + when arg begins with a +.  The\nindex of the next arg is stored in OPTIND.  The option argument, if any,  gets  stored\nin OPTARG.\nA  leading  :  in optstring causes getopts to store the letter of an invalid option in\nOPTARG, and to set vname to ?  for an unknown option and to : when a  required  option\nargument  is missing.  Otherwise, getopts prints an error message.  The exit status is\nnon-zero when there are no more options.\nThere is no way to specify any of the options :, +, -, ?, [, and ].  The option #  can\nonly be specified as the first option.\n\nhash [ -r ] [ utility ]\nhash displays or modifies the hash table with the locations of recently used programs.\nIf  given  no  arguments,  it  lists  all  command/path  associations (a.k.a. 'tracked\naliases') in the hash table. Otherwise, hash performs a PATH search for  each  utility\nsupplied and adds the result to the hash table.  The -r option empties the hash table.\nThis can also be achieved by resetting PATH.\n\nhist [ -e ename  ] [ -N num ] [ -nlr ] [ first [ last ] ]\nhist -s [ old=new ] [ command ]\nIn  the  first  form, a range of commands from first to last is selected from the last\nHISTSIZE commands that were typed at the terminal.  The arguments first and  last  may\nbe  specified  as a number or as a string.  A string is used to locate the most recent\ncommand starting with the given string.  A negative number is used as an offset to the\ncurrent command number.  If the -l option is selected,  the  commands  are  listed  on\nstandard  output.  Otherwise, the editor program ename is invoked on a file containing\nthese keyboard commands.  If ename is not supplied, then the  value  of  the  variable\nHISTEDIT  is  used.   If HISTEDIT is not set, then FCEDIT (default /bin/ed) is used as\nthe editor.  When editing is complete,  the  edited  command(s)  is  executed  if  the\nchanges  have been saved.  If last is not specified, then it will be set to first.  If\nfirst is not specified, the default is the previous command for editing  and  -16  for\nlisting.   The  option  -r  reverses  the order of the commands and the option -n sup‐\npresses command numbers when listing.  In the second form, command is  interpreted  as\nfirst  described  above and defaults to the last command executed.  The resulting com‐\nmand is executed after the optional substitution old=new is performed.  The option  -N\ncauses hist to start num commands back.\n\n‡ integer vname[=value] ...\nDeclares each vname to be a long integer number.  The same as typeset -li.\n\njobs [ -lnp ] [ job ... ]\nLists  information about each given job; or all active jobs if job is omitted.  The -l\noption lists process IDs in addition to the normal information.  The  -n  option  only\ndisplays  jobs  that have stopped or exited since last notified.  The -p option causes\nonly the process group to be listed.  See Jobs for a description of the format of job.\n\nkill [ -s signame ] job ...\nkill [ -n signum ] job ...\nkill -Ll [ sig ... ]\nSends either the TERM (terminate) signal or the specified signal to the specified jobs\nor processes.  Signals are either given by number with the -n option or by  name  with\nthe  -s  option (as given in <signal.h>, stripped of the prefix ``SIG''.  For backward\ncompatibility, the n and s can be omitted and the number or  name  placed  immediately\nafter  the  -.  If the signal being sent is TERM (terminate) or HUP (hangup), then the\njob or process will be sent a CONT (continue) signal if it is stopped.   The  argument\njob can be the process ID of a process that is not a member of one of the active jobs.\nSee  Jobs  for a description of the format of job.  In the third form, kill -l or kill\n-L, if sig is not specified, the signal names are listed.  The -l  option  lists  only\nthe  signal  names.   The  -L  option lists each signal name and corresponding number.\nOtherwise, for each sig that is a name, the corresponding  signal  number  is  listed.\nFor  each sig that is a number, the signal name corresponding to the least significant\n8 bits of sig is listed.\n\nlet arg ...\nEach arg is a separate arithmetic expression to be evaluated.  let only recognizes oc‐\ntal numbers starting with 0 when the set option letoctal is on.  See Arithmetic Evalu‐\nation above for a description of arithmetic expression evaluation.\nThe exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.\n\n‡ nameref vname[=refname] ...\nDeclares each vname to be a variable name reference.  The same as typeset -n.\n\nprint [ -CRenprsv ] [ -u unit ] [ -f format ] [ arg ... ]\nWith no options or with option - or --, each arg is printed on standard  output.   The\n-f  option  causes  the arguments to be printed as described by printf.  In this case,\nany e, n, r, R options are ignored.  Otherwise, unless the -C, -R, -r, or -v are spec‐\nified, the following escape conventions will be applied:\n\\a     The alert character (ASCII 07).\n\\b     The backspace character (ASCII 010).\n\\c     Causes print to end without processing more arguments and  not  adding  a  new-\nline.\n\\f     The formfeed character (ASCII 014).\n\\n     The newline character (ASCII 012).\n\\r     The carriage return character (ASCII 015).\n\\t     The tab character (ASCII 011).\n\\v     The vertical tab character (ASCII 013).\n\\E     The escape character (ASCII 033).\n\\\\     The backslash character \\.\n\\0x    The character defined by the 1, 2, or 3-digit octal string given by x.\n\nThe  -R  option will print all subsequent arguments and options other than -n.  The -e\ncauses the above escape conventions to be applied.  This is the default behavior.   It\nreverses  the effect of an earlier -r.  The -p option causes the arguments to be writ‐\nten onto the pipe of the process spawned with |& instead of standard output.   The  -v\noption  treats  each arg as a variable name and writes the value in the printf %B for‐\nmat.  The -C option treats each arg as a variable name and writes  the  value  in  the\nprintf  %#B format.  The -s option causes the arguments to be written onto the history\nfile instead of standard output.  The -u option can be used to  specify  a  one  digit\nfile  descriptor  unit number unit on which the output will be placed.  The default is\n1.  If the option -n is used, no new-line is added to the output.\n\nprintf [ -v vname ] format [ arg ... ]\nThe arguments arg are printed on standard output in accordance with the ANSI C format‐\nting rules associated with the format string format.  If the number of  arguments  ex‐\nceeds  the  number of format specifications, the format string is reused to format re‐\nmaining arguments.  The following extensions can also be used:\n%b     A %b format can be used instead of %s to cause escape sequences in  the  corre‐\nsponding arg to be expanded as described in print.\n%B     A  %B  option  causes each of the arguments to be treated as variable names and\nthe binary value of variable will be printed.  The alternate flag  #  causes  a\ncompound  variable to be output on a single line.  This is most useful for com‐\npound variables and variables whose attribute is -b.\n%H     A %H format can be used instead of %s to cause characters in arg that are  spe‐\ncial  in  HTML and XML to be output as their entity name.  The alternate flag #\nformats the output for use as a URI.\n%p     A %p format will convert the given number to hexadecimal.\n%P     A %P format can be used instead of %s to cause arg to be interpreted as an  ex‐\ntended regular expression and be printed as a shell pattern.\n%q     A  %q  format  can  be  used  instead of %s to cause the resulting string to be\nquoted in a manner than can be reinput to the shell.  When q is preceded by the\nalternative format specifier, #, the string is quoted in manner suitable  as  a\nfield in a .csv format file.\n%(date-format)T\nA %(date-format)T format can be used to treat an argument as a date/time string\nand to format the date/time according to the date-format.\n%Q     A %Q format will convert the given number of seconds to readable time.\n%R     A %R format can be used instead of %s to cause arg to be interpreted as a shell\npattern and to be printed as an extended regular expression.\n%Z     A %Z format will output a byte whose value is 0.\n%d     The  precision  field  of  the %d format can be followed by a .  and the output\nbase.  In this case, the # flag character causes base# to be  prepended.   When\nan  output base is specified without giving a precision (e.g.  %..2d), the pre‐\ncision defaults to 1 instead of 0.\n#      The # flag, when used with the %d format without an output base,  displays  the\noutput  in powers of 1000 indicated by one of the following suffixes: k M G T P\nE, and when used with the %i format displays the output in powers of 1024 indi‐\ncated by one of the following suffixes: Ki Mi Gi Ti Pi Ei.\n=      The = flag centers the output within the specified field width.\nL      The L flag, when used with the %c or %s formats, treats precision as  character\nwidth instead of byte count.\n,      The  ,  flag,  when  used with the %d or %f formats, separates groups of digits\nwith the grouping delimiter (, on groups of 3 in the C locale).\n\nThe -v option assigns the output directly to a variable instead of writing it to stan‐\ndard output. This is faster than capturing the output using a command substitution and\navoids the latter's stripping of final linefeed characters (\\n).  The  vname  argument\nshould  be  a  valid  variable  name,  optionally with one or more array subscripts in\nsquare brackets.  Note that square brackets should be quoted to avoid pathname  expan‐\nsion.\n\n\npwd [ -LP ]\nOutputs  the value of the current working directory.  The -L option is the default; it\nprints the logical name of the current directory.  If the -P option is given, all sym‐\nbolic links are resolved from the name.  The last instance of -L or -P on the  command\nline determines which method is used.\n\nread [ -ACSaprsv ] [ -d delim ] [ -n n ] [ -N n ] [ -t timeout ] [ -u unit ] [ vname?prompt ]\n[ vname ... ]\nThe  shell  input  mechanism.  One line is read and is broken up into fields using the\ncharacters in IFS as separators.  The escape character, \\, is used to remove any  spe‐\ncial meaning for the next character and for line continuation.  The first field is as‐\nsigned  to  the first vname, the second field to the second vname, etc., with leftover\nfields assigned to the last vname.  If vname is omitted, then REPLY is used as the de‐\nfault vname.  When vname has the binary attribute and -n or -N is specified, the bytes\nthat are read are stored directly into the variable.  If you  append  ?prompt  to  the\nfirst  vname,  then read will display prompt on standard error before reading if stan‐\ndard input is a terminal or pipe; the ? should be quoted to protect it  from  pathname\nexpansion.   The  exit  status  is  0 unless an end-of-file is encountered or read has\ntimed out.  The options for the read command have meaning as follows:\n-A      Causes the variable vname to be unset and each field that is read to be stored\nin successive elements of the indexed array vname.\n-C      Causes the variable vname to be read as a compound variable.  Blanks  will  be\nignored when finding the beginning open parenthesis.\n-N      Causes  n  bytes  to be read unless an end-of-file has been encountered or the\nread times out because of the -t option.\n-S      Causes the line to be treated like a record in a .csv format file so that dou‐\nble quotes can be used to allow the delimiter character and the new-line char‐\nacter to appear within a field.\n-a      Same as -A.\n-d      Causes the read to continue to the first character of  delim  instead  of  the\nnewline control character.  Multibyte characters for delim are not supported.\n-n      Causes at most n bytes to be read instead of a full line, but will return when\nreading from a slow device as soon as any characters have been read.\n-p      Input  is  read from the current co-process spawned by the shell using ⎪&.  An\nend-of-file causes read to disconnect the co-process so that  another  can  be\ncreated.\n-r      Raw mode. The \\ character is not treated specially.\n-s      The input will be saved as a command in the history file.\n-t      Used to specify a timeout in seconds when reading from a terminal or pipe.\n-u      This  option  can  be used to specify a one-digit file descriptor unit unit to\nread from.  The file descriptor can be opened with the exec or redirect built-\nin command.  If unit is p, input is read from the current co-process  as  with\nthe -p option.  The default value of unit is 0.\n-v      The value of the first vname will be used as a default value when reading from\na terminal device.\n\n†‡ readonly [ -p ] [ vname[=value] ] ...\nIf  vname  is  not given, the names and values of each variable with the read-only at‐\ntribute is printed with the values quoted in a manner that allows them to be re-input.\nThe -p option causes the word readonly to be inserted before each one.  Otherwise, the\ngiven vnames are marked read-only and these names cannot be changed by subsequent  as‐\nsignment.  Unlike typeset -r , readonly does not create a function-local scope and the\ngiven  vnames  are marked globally read-only by default.  When defining a type, if the\nvalue of a read-only subvariable is not defined, the value is required  when  creating\neach instance.\n"
                },
                {
                    "name": "redirect",
                    "content": "This  command only accepts input/output redirections.  It can open and close files and\nmodify file descriptors from 0 to 9 as specified by the input/output redirection  list\n(see  the  Input/Output  section  above), with the difference that the effect persists\npast the execution of the redirect command.  When invoking another program,  file  de‐\nscriptors  greater  than  2 that were opened with this mechanism are only passed on if\nthey are explicitly redirected to themselves as part of the invocation (e.g. 4>&4)  or\nif the posix option is set.\n\n† return [ n ]\nCauses a shell function, dot script (see . and source), or profile script to return to\nthe invoking shell environment with the exit status specified by n.  This status value\ncan  use  the  full  signed integer range as shown by the commands getconf INTMIN and\ngetconf INTMAX. A value outside that range will produce a warning and an exit  status\nof  128.   If  n is omitted, then the value of $? is assumed, i.e., the exit status of\nthe last command executed is passed on.  If return is invoked while not in a function,\ndot script, or profile script, then it behaves the same as exit.\n\n† set [ ±BCGHabefhkmnprstuvx ] [ ±o [ option ] ] ... [ ±A vname ]  [ arg ... ]\nThe options for this command have meaning as follows:\n-A      Array assignment.  Unset the variable vname  and  assign  values  sequentially\nfrom the arg list.  If +A is used, the variable vname is not unset first.\n-B      Enable brace group expansion. On by default, except if ksh is invoked as sh or\nrsh.\n-C      Prevents redirection > from truncating existing files.  Files that are created\nare  opened  with the OEXCL mode.  Requires >| to truncate a file when turned\non.\n-G      Enables recursive pathname expansion.  This adds the double-star pattern  to\nthe pathname expansion (see Pathname Expansion above).  By itself, it  matches\nthe  recursive  contents  of the current directory, which is to say, all files\nand directories in the current directory and in all its  subdirectories,  sub-\nsubdirectories, and so on.  If the pathname pattern ends in /, only directo‐\nries  and  subdirectories  are matched, including symbolic links that point to\ndirectories.  A prefixed directory name is not included in the results  unless\nthat  directory was itself found by a pattern. For example, dir/ matches the\nrecursive contents of dir but not dir itself, whereas  di[r]/  matches  both\ndir  itself and the recursive contents of dir.  Symbolic links to non-directo‐\nries are not followed.  Symbolic links to directories are followed if they are\nspecified literally or match a pattern as described under Pathname  Expansion,\nbut not if they result from a double-star pattern.\n-H      Enable  !-style  history  expansion  similar to csh(1).  See History Expansion\nabove.\n-a      All variables that are assigned a value while this option is on are  automati‐\ncally  exported,  unless  they have a dot in their name.  Variables created in\nnamespaces declared with the namespace keyword (see  Name  Spaces  above)  are\nonly exported while their name space is active.\n-b      Prints  job  completion  messages  as  soon  as a background job changes state\nrather than waiting for the next prompt.  If one of the shell line editors  is\nin use (see In-line Editing Options above), the completion message is inserted\ndirectly above the command line being typed.\n-e      Unless  contained  in a || or && command, or the command following an if while\nor until command or in the pipeline following !, if a command has  a  non-zero\nexit  status,  execute  the ERR trap, if set, and exit.  This mode is disabled\nwhile reading profiles.\n-f      Disables pathname expansion.\n-h      Obsolete; no effect.\n-k      All variable assignment arguments are placed in the environment for a command,\nnot just those that precede the command name.\n-m      Background jobs will run in a separate process group and  a  line  will  print\nupon  completion.  The exit status of background jobs is reported in a comple‐\ntion message.  A pipeline will not terminate until all component  commands  of\nthe  pipeline  have  terminated.   On systems with job control, this option is\nturned on automatically for interactive shells.\n-n      Read commands and check them for syntax errors, but do not execute them.   Ig‐\nnored for interactive shells.\n-o      The following argument can be one of the following option names:\nallexport\nSame as -a.\nbackslashctrl\nThe  backslash  character  \\ escapes the next control character in the\nemacs built-in editor and the next erase or kill character in  the  vi\nbuilt-in editor.  On by default.\nbgnice  All  background jobs are run at a lower priority.  This is the default\nmode.\nbraceexpand\nSame as -B.\nemacs   Activates the emacs-style command line editor.  See Emacs Editing Mode\nabove.\nerrexit Same as -e.\nfunctrace\nCauses the -x option's state and the DEBUG trap action to be inherited\nby functions defined using the function keyword (see Functions  above)\ninstead  of  being  reset to default.  Changes made to them within the\nfunction do not propagate back to the parent scope.   Similarly,  this\noption also causes the DEBUG trap action to be inherited by subshells.\nglobcasedetect\nWhen this option is turned on, globbing (see Pathname Expansion above)\nand  file  name  listing  and  completion (see In-line Editing Options\nabove) automatically become case-insensitive on file systems where the\ndifference between upper- and lowercase is  ignored  for  file  names.\nThis is transparently determined for each directory, so a path pattern\nthat  spans  multiple file systems can be part case-sensitive and part\ncase-insensitive.  In more precise terms,  each  slash-separated  path\nname  component pattern p is treated as ~(i:p) if its parent directory\nexists on a case-insensitive file system.  This option is only present\non operating systems that support case-insensitive file systems.\nglobstar\nSame as -G.\ngmacs   Activates the emacs-style command line editor with modified  ^T.   See\nEmacs Editing Mode above.\nhistexpand\nSame as -H.\nhistreedit\nIf  a  history  expansion (see -H) fails, the command line is reloaded\ninto the next prompt's edit buffer, allowing corrections.\nhistverify\nThe results of a history expansion (see -H) are not  immediately  exe‐\ncuted.   Instead,  the  expanded line is loaded into the next prompt's\nedit buffer, allowing further changes.\nignoreeof\nAn interactive shell will not exit on end-of-file.  The  command  exit\nmust be used.\nkeyword Same as -k.\nletoctal\nThe  let  command allows octal numbers starting with 0.  On by default\nif ksh is invoked as sh or rsh.\nmarkdirs\nAll directory names resulting from pathname expansion have a  trailing\n/ appended.\nmonitor Same as -m.\nmultiline\nThe  built-in  editors will use multiple lines on the screen for lines\nthat are longer than the width of the screen.  This may not  work  for\nall  terminals.   The shell uses the system default tput(1) command to\nobtain the terminal escape codes for the necessary operations.  Multi-\nline editing is disabled if this fails.  On most systems, setting  the\nTERM  variable  to your terminal's type and exporting it corrects this\nsituation.  The multiline  option  is  ineffectual  on  systems  whose\ntput(1) command supports neither terminfo(5) nor termcap(5) capability\nnames.\nnoclobber\nSame as -C.\nnoexec  Same as -n.\nnoglob  Same as -f.\nnolog   Obsolete; has no effect.\nnotify  Same as -b.\nnounset Same as -u.\npipefail\nThe exit status of the entire pipeline will be that of the last compo‐\nnent  command  that  exited with a non-zero exit status, or zero if no\ncommand exited with a non-zero exit status.  The shell will  wait  for\nall  component  commands of the pipeline to terminate, instead of only\nwaiting for the last component command.\nposix   Enables the POSIX standard mode for maximum compatibility  with  other\ncompliant shells. At the moment that the posix option is turned on, it\nalso  turns  on  letoctal and turns off -B/braceexpand; the reverse is\ndone when posix is turned back off. (These options can still  be  con‐\ntrolled  independently  in  between.) Furthermore, the posix option is\nautomatically turned on upon invocation if the shell is invoked as  sh\nor rsh, or if -o posix or --posix is specified on the shell invocation\ncommand  line,  or  when executing scripts without a #! path with this\noption active in the invoking shell. In that case, the  invoked  shell\nwill  not  import  type  attributes  for variables (such as integer or\nleft/right justify) from the environment.\nIn addition, while on, the posix option\n•  disables exporting variable type attributes to the environment  for\nother ksh processes to import;\n•  disallows brace expansion on the results of unquoted expansions (if\nthe -B/braceexpand option is turned back on);\n•  disables  the special handling of repeated isspace class characters\nin the IFS variable;\n•  causes file descriptors > 2 to be left open when  invoking  another\nprogram;\n•  disables the &> redirection shorthand;\n•  disables  fast  filescan  loops  of type while inputredirection ;do\nlist ;done;\n•  makes the <> redirection operator default to  redirecting  standard\ninput if no file descriptor number precedes it;\n•  causes  the shell to use a standard UNIX pipe(2) instead of a sock‐\netpair(2) to connect commands in a pipeline (when reading  directly\nfrom a pipeline, the <#pattern and <##pattern redirection operators\nwill  not  work and the -n option to the read built-in will not re‐\nturn early when reading from a slow device);\n•  disables the special floating point constants Inf and NaN in arith‐\nmetic evaluation so that, e.g., $((inf)) and $((nan)) refer to  the\nvariables by those names;\n•  enables  the  recognition of a leading zero as introducing an octal\nnumber in all arithmetic evaluation contexts,  except  in  the  let\nbuilt-in while letoctal is off;\n•  disables  zero-padding  of  seconds  in  the output of the time and\ntimes built-ins;\n•  stops the . command (but not source) from looking up functions  de‐\nfined with the function syntax;\n•  disables the recognition of unexpanded shell arithmetic expressions\nfor the numerical conversion specifiers of the printf built-in com‐\nmand,  causing  them  to  print a warning for operands that are not\nvalid decimal, 0x-prefixed hexadecimal or 0-prefixed octal numbers;\n•  disables the special handling of /dev/fd/n in  file  existence  and\naccess test operators in test/[ and [[, causing these to operate on\nthe file /dev/fd/n in the file system;\n•  disables the recognition of unexpanded shell arithmetic expressions\nin  the  numerical comparison operators -eq, -ne, -gt, -ge, -lt and\n-le of the test/[ built-in command, causing  them  to  accept  only\ndecimal numbers as operands;\n•  changes the test/[ built-in command to make its deprecated expr1 -a\nexpr2 and expr1 -o expr2 operators work even if expr1 equals \"!\" or\n\"(\" (which means the nonstandard unary -a file and -o option opera‐\ntors cannot be directly negated using ! or wrapped in parentheses);\nand\n•  disables a hack that makes test -t ([ -t ]) equivalent to test -t 1\n([ -t 1 ]).\nprivileged\nSame as -p.\nshowme  When enabled, simple commands or pipelines preceded by a semicolon (;)\nwill be displayed as if the xtrace option were enabled but will not be\nexecuted.  Otherwise, the leading ; will be ignored.\ntrackall\nSame as -h.\nverbose Same as -v.\nvi      Activates  the  vi-style command line editor, initially in input mode.\nSee Vi Editing Mode above.\nviraw   Obsolete; has no effect.\nxtrace  Same as -x.\n\nIf no option name is supplied, then the current option settings are printed.\n\n-p      Disables  processing  of  the  $HOME/.profile   file   and   uses   the   file\n/etc/suidprofile  instead  of the ENV file.  This mode is on whenever the ef‐\nfective UID (GID) is not equal to the real UID (GID).  Turning this off causes\nthe effective UID and GID to be set to the real UID and GID.\n-r      Enables the restricted shell.  This option cannot be unset once set.\n-s      Sort the positional parameters lexicographically.\n-t      (Obsolete).  Exit after reading and executing one command.\n-u      Treat unset parameters as an error when substituting.  $@ and $* are exempt.\n-v      Print shell input lines as they are read.\n-x      Print commands and their arguments as they are executed.\n--      Do not change any of the options; useful in setting $1 to  a  value  beginning\nwith -.  If no arguments follow this option then the positional parameters are\nunset.\n\nAs  an  obsolete  feature, if the first arg is - then the -x and -v options are turned\noff and the next arg is treated as the first argument.  Using + rather than  -  causes\nthese options to be turned off.  These options can also be used upon invocation of the\nshell.   The  current  set of options may be found in $-.  Unless -A is specified, the\nremaining arguments are positional parameters and are assigned, in  order,  to  $1  $2\n....   If  no  arguments  are  given,  then  the names and values of all variables are\nprinted on the standard output.\n\n† shift [ n ]\nThe positional parameters from $n+1 ...  are renamed $1 ... , default n is 1.  The pa‐\nrameter n can be any arithmetic expression that evaluates  to  a  non-negative  number\nless than or equal to $#.\n\nsleep [ -s ] duration\nSuspends execution for the number of decimal seconds or fractions of a second given by\nduration.  duration can be an integer, floating point value or ISO 8601 duration spec‐\nifying  the length of time to sleep.  The option -s causes the sleep builtin to termi‐\nnate when it receives any signal.  If duration is not specified  in  conjunction  with\n-s, sleep will wait for a signal indefinitely.\n\nsource name [ arg ... ]\nSame as ., except it is not treated as a special built-in command.\n\nstop job ...\nSends  a SIGSTOP signal to one or more processes specified by job, suspending them un‐\ntil they receive SIGCONT.  The same as kill -s STOP.\n"
                },
                {
                    "name": "suspend",
                    "content": "Sends a SIGSTOP signal to the main shell process, suspending the script or child shell\nsession until it receives SIGCONT (for instance, when typing fg in the parent  shell).\nEquivalent  to  kill -s STOP \"$$\",  except  that it accepts no operands and refuses to\nsuspend a login shell.\n\ntest expression\nThe test and [ commands execute conditional expressions similar to those specified for\nthe [[ compound command under Conditional Expressions above, but with  several  impor‐\ntant differences. The =, == and != operators test for string (in)equality without pat‐\ntern  matching;  ==  is  nonstandard  and  unportable. The && and || operators are not\navailable. Instead, the -a and -o binary operators can be used, but they  are  fraught\nwith  pitfalls due to grammatical ambiguities and therefore deprecated in favor of in‐\nvoking separate test commands. Most importantly, as test and [ are simple regular com‐\nmands, field splitting and pathname expansion are performed on all their arguments and\nall aspects of regular shell grammar (such as redirection) remain active. This is usu‐\nally harmful, so care must be taken to quote arguments and expansions to  avoid  this.\nTo  avoid  the many pitfalls arising from these issues, the [[ compound command should\nbe used instead. The primary purpose of the test and [ commands is compatibility  with\nother shells that lack [[.\n\nThe  test/[  command  does not parse options except if there are two arguments and the\nsecond is --. To access the inline documentation with an option  such  as  --man,  you\nneed one of the forms test --man -- or [ --man -- ].\n\ntimes  Displays  the  accumulated  user and system CPU times, one line with the times used by\nthe shell and another with those used by all of the shell's child  processes.  No  op‐\ntions are supported.  Seconds are zero-padded unless the posix shell option is on.\n\n† trap [ -p ] [ action ] [ sig ] ...\nThe -p option causes the trap action associated with each trap as specified by the ar‐\nguments  to  be printed with appropriate quoting.  Otherwise, action will be processed\nas if it were an argument to eval when the shell receives signal(s) sig.  Each sig can\nbe given as a number or as the name of the signal.  Trap commands are executed in  or‐\nder of signal number.  Any attempt to set a trap on a signal that was ignored on entry\nto the current shell is ineffective.  If action is omitted and the first sig is a num‐\nber, or if action is -, then the trap(s) for each sig are reset to their original val‐\nues.   If  action is the empty string, then this signal is ignored by the shell and by\nthe commands it invokes.  If sig is ERR then action will be executed whenever  a  com‐\nmand  has a non-zero exit status.  If sig is DEBUG then action will be executed before\neach command.  The variable .sh.command will contain the current command line when ac‐\ntion is running, in the same format as the output generated by the xtrace option  (mi‐\nnus  the  preceding PS4 prompt).  If the exit status of the trap is 2 the command will\nnot be executed.  If the exit status of the trap is 255 and inside a function or a dot\nscript, the function or dot script will return.  If sig is 0  or  EXIT  and  the  trap\nstatement  is  executed  inside  the body of a function defined with the function name\nsyntax, then the command action is executed after the function completes.  If sig is 0\nor EXIT for a trap set outside any function then the command  action  is  executed  on\nexit  from the shell.  If sig is KEYBD, then action will be executed whenever a key is\nread while in emacs, gmacs, or vi mode.  The trap command with no arguments  prints  a\nlist of commands associated with each signal number.\n\nAn  exit  or return without an argument in a trap action will preserve the exit status of the\ncommand that invoked the trap.\n\ntrue   Does nothing, and exits 0. Used with while for infinite loops.\n\ntype [ -afpPqt ] name ...\nThe same as whence -v.\n\n†‡ typeset [ ±ACHSbflmnprstux ] [ ±EFLRXZi[n] ]   [ +-M  [ mapname ] ] [ -T  [ tname=(as‐\nsignlist) ] ] [ -h str ] [ -a [ [type] ] ] [ vname[=value ]  ] ...\nSets attributes and values for shell variables and functions.  When invoked  inside  a\nfunction  defined  with the function name syntax, a new instance of the variable vname\nis created, and the variable's value and type are  restored  when  the  function  com‐\npletes.  The following list of attributes may be specified:\n-A     Declares  vname to be an associative array.  Subscripts are strings rather than\narithmetic expressions.\n-C     Causes each vname to be a compound variable. If value names  a  compound  vari‐\nable, it is copied into vname.  Otherwise, the empty compound value is assigned\nto vname.\n-a     Declares vname to be an indexed array. This is the default.  Subscripts are nu‐\nmerical  and  start  at 0.  To make it possible to use alphanumeric enumeration\nconstants of a given type as subscripts, an option value of the form [type] can\nbe specified (including the  surrounding  square  brackets),  which  should  be\nquoted to avoid pathname expansion), where type must be the name of an enumera‐\ntion type created with the enum command.\n-E     Declares  vname  to  be a double precision floating point number.  If n is non-\nzero, it defines the number of significant figures that are used when expanding\nvname.  Otherwise, ten significant figures will be used.\n-F     Declares vname to be a double precision floating point number.  If  n  is  non-\nzero,  it  defines  the  number of places after the decimal point that are used\nwhen expanding vname.  Otherwise ten places after the  decimal  point  will  be\nused.\n-H     This option provides UNIX to host-name file mapping on non-UNIX machines.\n-L     Left  justify  and  remove leading blanks from value.  If n is non-zero, it de‐\nfines the width of the field, otherwise it is determined by the  width  of  the\nvalue  of  first assignment.  When the variable is assigned to, it is filled on\nthe right with blanks or truncated, if necessary, to fit into the  field.   The\n-R option is turned off.\n-M     Use  the  character mapping mapping defined by wctrans(3).  such as tolower and\ntoupper when assigning a value to each of the specified operands.  When mapping\nis specified and there are not operands, all variables that  use  this  mapping\nare  written  to  standard  output.   When  mapping is omitted and there are no\noperands, all mapped variables are written to standard output.\n-R     Right justify and fill with leading blanks.  If n is non-zero, it  defines  the\nwidth  of  the  field,  otherwise it is determined by the width of the value of\nfirst assignment.  The field is left filled with blanks or truncated  from  the\nend if the variable is reassigned.  The -L option is turned off.\n-S     When  used within the assignlist of a type definition, it causes the specified\nsubvariable to be shared by all instances of the  type.   When  used  inside  a\nfunction  defined with the function reserved word, the specified variables will\nhave function static scope.  Otherwise, the variable is unset prior to process‐\ning the assignment list.\n-T     If followed by tname, it creates a type named by tname using the  compound  as‐\nsignment  assignlist  to tname.  Otherwise, it writes all the type definitions\nto standard output.\n-X     Declares vname to be a double precision floating point number and expands using\nthe %a format of ISO-C99.  If n is non-zero, it defines the number of hex  dig‐\nits  after  the  radix point that is used when expanding vname.  The default is\n10.\n-Z     Right justify and fill with leading zeros if the first non-blank character is a\ndigit and the -L option has not been set.  Remove leading zeros if the  -L  op‐\ntion  is also set.  If n is non-zero, it defines the width of the field, other‐\nwise it is determined by the width of the value of first assignment.\n-f     The names refer to function names rather than variable names.   No  assignments\ncan be made and the only other valid options are -S, -t, -u and -x.  The -S can\nbe  used with discipline functions defined in a type to indicate that the func‐\ntion is static.  For a static function, the same method will be used by all in‐\nstances of that type no matter which instance references it.  In  addition,  it\ncan  only use value of variables from the original type definition.  These dis‐\ncipline functions cannot be redefined in any  type  instance.   The  -t  option\nturns  on execution tracing for this function.  The -u option causes this func‐\ntion to be marked undefined.  The FPATH variable will be searched to  find  the\nfunction  definition when the function is referenced.  If no options other than\n-f is specified, then the function definition will  be  displayed  on  standard\noutput.   If +f is specified, then a line containing the function name followed\nby a shell comment containing the line number and path name of the  file  where\nthis  function  was defined, if any, is displayed.  The exit status can be used\nto determine whether the function is defined so that typeset  -f  .sh.math.name\nwill return 0 when math function name is defined and non-zero otherwise.\n-b     The variable can hold any number of bytes of data.  The data can be text or bi‐\nnary.   The  value is represented by the base64 encoding of the data.  If -Z is\nalso specified, the size in bytes of the data in the buffer will be  determined\nby  the  size associated with the -Z.  If the base64 string assigned results in\nmore data, it will be truncated.  Otherwise, it will be filled with bytes whose\nvalue is zero.  The printf format %B can be used to output the actual  data  in\nthis buffer instead of the base64 encoding of the data.\n-g     Forces variables to be created or modified at the global scope, even when type‐\nset  is  executed  in a function defined by the function name syntax (see Func‐\ntions above) or in a name space (see Name Spaces above).\n-h     Used within type definitions to add  information  when  generating  information\nabout  the  subvariable  on the man page.  It is ignored when used outside of a\ntype definition.  When used with -f the information is associated with the cor‐\nresponding discipline function.\n-i     Declares vname to be represented internally as integer.  The right hand side of\nan assignment is evaluated as an arithmetic expression when assigning to an in‐\nteger.  If n is non-zero, it defines the output arithmetic base, otherwise  the\noutput base will be ten.\n-l     Used  with  -i,  -E or -F, to indicate long integer, or long float.  Otherwise,\nall uppercase characters are converted to lowercase.  The uppercase option, -u,\nis turned off.  Equivalent to -M tolower .\n-m     Moves or renames the variable.  The value is the name of a variable whose value\nwill be moved to vname.  The original variable will be unset.  Cannot  be  used\nwith any other options.\n-n     Declares  vname  to be a reference to the variable whose name is defined by the\nvalue of variable vname.  This is usually used to reference a variable inside a\nfunction whose name has been passed as an argument.  Cannot be used with  other\noptions except -g.\n-p     The  name,  attributes  and values for the given vnames are written on standard\noutput in a form that can be used as shell input.  If +p is specified, then the\nvalues are not displayed.\n-r     The given vnames are marked read-only and these names cannot be changed by sub‐\nsequent assignment.\n-s     When given along with -i, restricts integer size to short.\n-t     Tags the variables.  Tags are user definable and have no special meaning to the\nshell.\n-u     When given along with -i, specifies unsigned integer.  Otherwise, all lowercase\ncharacters are converted to uppercase.  The lowercase  option,  -l,  is  turned\noff.  Equivalent to -M toupper .\n-x     The  given  vnames are marked for automatic export to the environment of subse‐\nquently-executed commands.  Variables whose names contain a .   cannot  be  ex‐\nported.\n\nThe  -i,  -F, -E, and -X options cannot be specified along with -R, -L, or -Z.  The -b\noption cannot be specified along with -L, -u, or -l.  The -f, -m, -n, and  -T  options\ncannot be used together with any other option.\n\nUsing  +  rather  than - causes these options to be turned off.  If no vname arguments\nare given, a list of vnames (and optionally the values) of the variables  is  printed.\n(Using  +  rather  than  - keeps the values from being printed.)  The -p option causes\ntypeset followed by the option letters to be printed before each name rather than  the\nnames  of  the  options.   If  any option other than -p is given, only those variables\nwhich have all of the given options are printed.  Otherwise, the vnames and attributes\nof all variables that have attributes are printed.\n\nulimit [ -HSaMctdfkxlqenVuPpmrRbiswTv ] [ limit ]\nSet or display a resource limit.  The available  resource  limits  are  listed  below.\nMany  systems  do  not support one or more of these limits.  The limit for a specified\nresource is set when limit is specified.  The value of limit can be a  number  in  the\nunit  specified  below  with each resource, or the value unlimited.  The -H and -S op‐\ntions specify whether the hard limit or the soft limit for the given resource is  set.\nA  hard limit cannot be increased once it is set.  A soft limit can be increased up to\nthe value of the hard limit.  If neither the H nor S option is  specified,  the  limit\napplies  to  both.   The  current resource limit is printed when limit is omitted.  In\nthis case, the soft limit is printed unless H is specified.  When more  than  one  re‐\nsource is specified, then the limit name and unit is printed before the value.\n-a     Lists all of the current resource limits.\n-b     The socket buffer size in bytes.\n-c     The number of 512-byte blocks on the size of core dumps.\n-d     The number of K-bytes on the size of the data area.\n-e     The scheduling priority.\n-f     The  number  of  512-byte  blocks  on  files that can be written by the current\nprocess or by child processes (files of any size may be read).\n-i     The signal queue size.\n-k     The max number of kqueues created by the current user.\n-l     The locked address space in K-bytes.\n-M     The address space limit in K-bytes.\n-m     The number of K-bytes on the size of physical memory.\n-n     The number of file descriptors plus 1.\n-P     The max number of pseudo-terminals created by the current user.\n-p     The number of 512-byte blocks for pipe buffering.\n-q     The message queue size in K-bytes.\n-R     The max time a real-time process can run before blocking, in microseconds.   If\nthis limit is exceeded the process is sent a SIGXCPU signal.\n-r     The max real-time priority.\n-s     The number of K-bytes on the size of the stack area.\n-T     The number of threads.\n-t     The number of CPU seconds to be used by each process.\n-u     The number of processes.\n-V     The number of open vnode monitors.\n-v     The number of K-bytes for virtual memory.\n-w     The swap size in K-bytes.\n-x     The number of file locks.\n\nIf no option is given, -f is assumed.\n\numask [ -S ] [ mask ]\nThe  user file-creation mask is set to mask (see umask(2)).  mask can either be an oc‐\ntal number or a symbolic value as described in  chmod(1).   If  a  symbolic  value  is\ngiven,  the  new  umask  value is the complement of the result of applying mask to the\ncomplement of the previous umask value.  If mask is omitted, the current value of  the\nmask  is  printed.   The  -S option causes the mode to be printed as a symbolic value.\nOtherwise, the mask is printed in octal.\n\nunalias [ -a ] name ...\nThe aliases given by the list of names are removed from the alias list.  The -a option\ncauses all the aliases to be unset.\n\n† unset [ -fnv ] vname ...\nThe variables given by the list of vnames are unassigned, i.e.,  except  for  subvari‐\nables  within  a  type, their values and attributes are erased.  For subvariables of a\ntype, the values are reset to the default value from the  type  definition.   Readonly\nvariables  cannot be unset.  If the -f option is set, then the names refer to function\nnames.  If the -v option is set, then the names refer to variable names.  The  -f  op‐\ntion overrides -v.  If -n is set and name is a name reference, then name will be unset\nrather than the variable that it references.  The default is equivalent to -v.  Unset‐\nting  LINENO,  MAILCHECK,  OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and  removes their\nspecial meaning even if they are subsequently assigned to.\n\nwait [ job ... ]\nWait for the specified job and report its termination status.  If job  is  not  given,\nthen  all  currently active child processes are waited for.  The exit status from this\ncommand is that of the last process waited for if job is specified;  otherwise  it  is\nzero.  See Jobs for a description of the format of job.\n\nwhence [ -afpPqtv ] name ...\nFor each name, indicate how it would be interpreted if used as a command name.\nThe  -v  option  produces  a  more verbose report.  The -f option skips the search for\nfunctions.  The -p and -P options do a path search for name even if name is an  alias,\na function, or a reserved word.  Both of these options turn off the -v option.  The -q\noption  causes  whence  to enter quiet mode.  whence will return zero if all arguments\nare built-ins, functions, or are programs found on the path.  The -t option only  out‐\nputs  the  type of the given command.  Like -p and -P, -t will turn off the -v option.\nThe -a option is similar to the -v option but causes all interpretations of the  given\nname to be reported.\n"
                },
                {
                    "name": "Invocation.",
                    "content": "If  the shell is invoked by exec(2), initialization depends on argument zero ($0) as follows.\nIf the first character of $0 is -, or the -l option is given on the invocation command  line,\nthen  the shell is assumed to be a login shell.  If the basename of the command path in $0 is\nrsh, rksh, or krsh, then the shell becomes restricted.  If the basename is sh or rsh, or  the"
                },
                {
                    "name": "-o posix",
                    "content": "full POSIX compliance mode (see the set builtin command above for more  information).   After\nthis,  if  the shell was assumed to be a login shell, commands are read from /etc/profile and\nthen from $HOME/.profile if it exists.  Alternatively, the option -l causes the shell  to  be\ntreated  as  a  login  shell.   Next, for interactive shells, commands are read from the file\nnamed by ENV if the file exists, its name being determined by performing parameter expansion,\ncommand substitution, and arithmetic expansion on the value of that environment variable.  If\nthe -s option is not present and arg and a file by the name of arg exists, then it reads  and\nexecutes  this  script.   Otherwise,  if the first arg does not contain a /, a path search is\nperformed on the first arg to determine the name of the script to execute.   The  script  arg\nmust  have  execute  permission  and  any setuid and setgid settings will be ignored.  If the\nscript is not found on the path, arg is processed as if it named a built-in command or  func‐\ntion.   Commands  are  then read as described below; the following options are interpreted by\nthe shell when it is invoked:\n",
                    "flag": "-o"
                },
                {
                    "name": "-D",
                    "content": "dard output and the shell will exit.  This set of strings will be subject to language\ntranslation when the locale is not C or POSIX.  No commands will be executed.\n",
                    "flag": "-D"
                },
                {
                    "name": "-E  -o rc  --rc",
                    "content": "Read the file named by the ENV variable or by $HOME/.kshrc if not defined  after  the\nprofiles.  On by default for interactive shells. Use +E, +o rc or --norc to turn off.\n",
                    "flag": "-o",
                    "long": "--rc"
                },
                {
                    "name": "-c",
                    "content": "present, becomes that script's command name ($0).  Any third and further args  become\npositional parameters starting at $1.\n",
                    "flag": "-c"
                },
                {
                    "name": "-s",
                    "content": "($0) cannot be set.  Any args become the positional parameters starting at $1.   This\noption is forced on if no arg is given and is ignored if -c is also specified.\n",
                    "flag": "-s"
                },
                {
                    "name": "-i  -o interactive  --interactive",
                    "content": "If  the  -i option is present or if the shell's standard input and standard error are\nattached to a terminal (as told by tcgetattr(3)), then this shell is interactive.  In\nthis case TERM is ignored (so that kill 0 does not kill  an  interactive  shell)  and\nINTR  is  caught  and ignored (so that wait is interruptible).  In all cases, QUIT is\nignored by the shell.\n",
                    "flag": "-o",
                    "long": "--interactive"
                },
                {
                    "name": "-r  -o restricted  --restricted",
                    "content": "If the -r option is present, the shell is a restricted shell.\n\nThe remaining options and arguments are described under the set command above.  An optional -\nas the first argument is ignored.\n",
                    "flag": "-o",
                    "long": "--restricted"
                },
                {
                    "name": "Rksh Only.",
                    "content": "Rksh is used to set up login names and execution environments  whose  capabilities  are  more\ncontrolled  than  those of the standard shell.  The actions of rksh are identical to those of\nksh, except that the following are disallowed:\n\n•      unsetting the restricted option\n\n•      changing directory (see cd(1))\n\n•      setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH\n\n•      specifying path or command names containing /\n\n•      redirecting output (>, >|, <>, and >>)\n\n•      adding or deleting built-in commands\n\n•      using command -p to invoke a command\n\nThe restrictions above are enforced after .profile and the ENV files are interpreted.\n\nWhen a command to be executed is found to be a shell procedure, rksh invokes ksh  to  execute\nit.  Thus, it is possible to provide to the end-user shell procedures that have access to the\nfull  power of the standard shell, while imposing a limited menu of commands; this scheme as‐\nsumes that the end-user does not have write and execute permissions in the same directory.\n\nThe net effect of these rules is that the writer of the .profile has  complete  control  over\nuser  actions,  by performing guaranteed setup actions and leaving the user in an appropriate\ndirectory (probably not the login directory).\n\nThe system administrator often sets up a directory of commands (e.g., /usr/rbin) that can  be\nsafely invoked by rksh.\n"
                }
            ]
        },
        "EXIT STATUS": {
            "content": "Errors  detected  by  the  shell, such as syntax errors, cause the shell to return a non-zero\nexit status.  If the shell is being used non-interactively, then execution of the shell  file\nis  abandoned  unless  the error occurs inside a subshell in which case the subshell is aban‐\ndoned.  Otherwise, the shell returns the exit status of the last command executed  (see  also\nthe  exit command above).  Run time errors detected by the shell are reported by printing the\ncommand or function name and the error condition.  If the line number that the error occurred\non is greater than one, then the line number is also printed in square  brackets  ([])  after\nthe command or function name.\n",
            "subsections": []
        },
        "FILES": {
            "content": "",
            "subsections": [
                {
                    "name": "/etc/profile",
                    "content": "The system wide initialization file, executed for login shells.\n"
                },
                {
                    "name": "$HOME/.profile",
                    "content": "The personal initialization file, executed for login shells after /etc/profile.\n"
                },
                {
                    "name": "$HOME/.kshrc",
                    "content": "Default  personal initialization file, executed for interactive shells when ENV is not\nset.\n"
                },
                {
                    "name": "/etc/suid_profile",
                    "content": "Alternative initialization file, executed instead of the personal initialization  file\nwhen the real and effective user or group ID do not match.\n"
                },
                {
                    "name": "/dev/null",
                    "content": "The null device.\n"
                }
            ]
        },
        "SEE ALSO": {
            "content": "cat(1),  cd(1),  chmod(1),  cut(1),  date(1),  echo(1),  emacs(1), env(1), gmacs(1), grep(1),\nstty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), getpwnam(3), ioctl(2), lseek(2),\npaste(1), pathconf(2), pipe(2), sysconf(3), umask(2), ulimit(2),  wait(2),  strftime(3),  wc‐\ntrans(3), rand(3), profile(5), environ(7).\n\nMorris I. Bolsky and David G. Korn, The New KornShell Command and Programming Language, Pren‐\ntice Hall, 1995.\n\nPOSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.\n",
            "subsections": []
        },
        "CAVEATS": {
            "content": "If  a  command is executed, and then a command with the same name is installed in a directory\nin the search path before the directory where the original command was found, the shell  will\ncontinue  to  exec  the original command.  Use the hash command or the -t option of the alias\ncommand to correct this situation.\n\nUsing the hist built-in command within a compound command will cause  the  whole  command  to\ndisappear from the history file.\n\nThe  built-in  command  . file reads the whole file before any commands are executed.  There‐\nfore, alias and unalias commands in the file will not apply to any commands  defined  in  the\nfile.\n\nTraps  are  not  processed  while a job is waiting for a foreground process.  Thus, a trap on\nCHLD won't be executed until the foreground job terminates.\n\nIn locales that use a multibyte character set such as UTF-8, the KEYBD trap is only triggered\nfor ASCII characters (1-127).\n\nIt is a good idea to leave a space after the comma operator in arithmetic expressions to pre‐\nvent the comma from being interpreted as the decimal point character in certain locales.\n\nKSH(1)",
            "subsections": []
        }
    },
    "summary": "ksh, rksh - KornShell, a standard/restricted command and programming language",
    "flags": [
        {
            "flag": "-E",
            "long": null,
            "arg": null,
            "description": "it is expanded. The optional option argument n defines the number of significant figures. The -F option causes the expansion to be represented as a floating decimal number when it is expanded. The -X option causes the expansion to be represented using the %a format defined by ISO C-99. The optional option argument n defines the number of places after the decimal (or radix) point in this case. An internal integer representation of a variable can be specified with the -i [n] option of the typeset special built-in command. The optional option argument n specifies an arithmetic base to be used when expanding the variable. If you do not specify an arithmetic base, base 10 will be used. Arithmetic evaluation is performed on the value of each assignment to a variable with the -E,"
        },
        {
            "flag": "-i",
            "long": null,
            "arg": null,
            "description": "integer causes the fractional part to be truncated."
        },
        {
            "flag": "-T",
            "long": null,
            "arg": null,
            "description": "specified as an option argument to -T, is set with a compound variable assignment that de‐ fines the type. Function definitions can appear inside the compound variable assignment and these become discipline functions for this type and can be invoked or redefined by each in‐ stance of the type. The function name create is treated specially. It is invoked for each instance of the type that is created but is not inherited and cannot be redefined for each instance. When a type is defined a special built-in command of that name is added. These built-ins are declaration commands and follow the same expansion rules as the built-in commands described below that are marked with a ‡ symbol. These commands can subsequently be used inside further type definitions. The man page for these commands can be generated by using the --man option or any of the other -- options described with getopts. The -r, -a, -A, -h, and -S options of typeset are permitted with each of these new built-ins. An instance of a type is created by invoking the type name followed by one or more instance names. Each instance of the type is initialized with a copy of the subvariables except for subvariables that are defined with the -S option. Variables defined with the -S are shared by all instances of the type. Each instance can change the value of any subvariable and can also define new discipline functions of the same names as those defined by the type defini‐ tion as well as any standard discipline names. No additional subvariables can be defined for any instance. When defining a type, if the value of a subvariable is not set and the -r attribute is speci‐ fied, it causes the subvariable to be a required subvariable. Whenever an instance of a type is created, all required subvariables must be specified. These subvariables become read-only in each instance. When unset is invoked on a subvariable within a type, and the -r attribute has not been spec‐ ified for this field, the value is reset to the default value associative with the type. In‐ voking unset on a type instance not contained within another type deletes all subvariables and the variable itself. A type definition can be derived from another type definition by defining the first subvari‐ able name as and defining its type as the base type. Any remaining definitions will be ad‐ ditions and modifications that apply to the new type. If the new type name is the same as that of the base type, the type will be replaced and the original type will no longer be ac‐ cessible. The typeset command with the -T and no option argument or operands will write all the type definitions to standard output in a form that can be read in to create all they types."
        },
        {
            "flag": "-o",
            "long": null,
            "arg": null,
            "description": "full POSIX compliance mode (see the set builtin command above for more information). After this, if the shell was assumed to be a login shell, commands are read from /etc/profile and then from $HOME/.profile if it exists. Alternatively, the option -l causes the shell to be treated as a login shell. Next, for interactive shells, commands are read from the file named by ENV if the file exists, its name being determined by performing parameter expansion, command substitution, and arithmetic expansion on the value of that environment variable. If the -s option is not present and arg and a file by the name of arg exists, then it reads and executes this script. Otherwise, if the first arg does not contain a /, a path search is performed on the first arg to determine the name of the script to execute. The script arg must have execute permission and any setuid and setgid settings will be ignored. If the script is not found on the path, arg is processed as if it named a built-in command or func‐ tion. Commands are then read as described below; the following options are interpreted by the shell when it is invoked:"
        },
        {
            "flag": "-D",
            "long": null,
            "arg": null,
            "description": "dard output and the shell will exit. This set of strings will be subject to language translation when the locale is not C or POSIX. No commands will be executed."
        },
        {
            "flag": "-o",
            "long": "--rc",
            "arg": null,
            "description": "Read the file named by the ENV variable or by $HOME/.kshrc if not defined after the profiles. On by default for interactive shells. Use +E, +o rc or --norc to turn off."
        },
        {
            "flag": "-c",
            "long": null,
            "arg": null,
            "description": "present, becomes that script's command name ($0). Any third and further args become positional parameters starting at $1."
        },
        {
            "flag": "-s",
            "long": null,
            "arg": null,
            "description": "($0) cannot be set. Any args become the positional parameters starting at $1. This option is forced on if no arg is given and is ignored if -c is also specified."
        },
        {
            "flag": "-o",
            "long": "--interactive",
            "arg": null,
            "description": "If the -i option is present or if the shell's standard input and standard error are attached to a terminal (as told by tcgetattr(3)), then this shell is interactive. In this case TERM is ignored (so that kill 0 does not kill an interactive shell) and INTR is caught and ignored (so that wait is interruptible). In all cases, QUIT is ignored by the shell."
        },
        {
            "flag": "-o",
            "long": "--restricted",
            "arg": null,
            "description": "If the -r option is present, the shell is a restricted shell. The remaining options and arguments are described under the set command above. An optional - as the first argument is ignored."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "cat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/cat/1/json"
        },
        {
            "name": "cd",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/cd/1/json"
        },
        {
            "name": "chmod",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/chmod/1/json"
        },
        {
            "name": "cut",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/cut/1/json"
        },
        {
            "name": "date",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/date/1/json"
        },
        {
            "name": "echo",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/echo/1/json"
        },
        {
            "name": "emacs",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/emacs/1/json"
        },
        {
            "name": "env",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/env/1/json"
        },
        {
            "name": "gmacs",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/gmacs/1/json"
        },
        {
            "name": "grep",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/grep/1/json"
        },
        {
            "name": "stty",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/stty/1/json"
        },
        {
            "name": "test",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/test/1/json"
        },
        {
            "name": "umask",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/umask/1/json"
        },
        {
            "name": "vi",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/vi/1/json"
        },
        {
            "name": "dup",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/dup/2/json"
        },
        {
            "name": "exec",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/exec/2/json"
        },
        {
            "name": "fork",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/fork/2/json"
        },
        {
            "name": "getpwnam",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/getpwnam/3/json"
        },
        {
            "name": "ioctl",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/ioctl/2/json"
        },
        {
            "name": "lseek",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/lseek/2/json"
        },
        {
            "name": "paste",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/paste/1/json"
        },
        {
            "name": "pathconf",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/pathconf/2/json"
        },
        {
            "name": "pipe",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/pipe/2/json"
        },
        {
            "name": "sysconf",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/sysconf/3/json"
        },
        {
            "name": "umask",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/umask/2/json"
        },
        {
            "name": "ulimit",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/ulimit/2/json"
        },
        {
            "name": "wait",
            "section": "2",
            "url": "https://www.chedong.com/phpMan.php/man/wait/2/json"
        },
        {
            "name": "strftime",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/strftime/3/json"
        },
        {
            "name": "trans",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/trans/3/json"
        },
        {
            "name": "rand",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/rand/3/json"
        },
        {
            "name": "profile",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/profile/5/json"
        },
        {
            "name": "environ",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/environ/7/json"
        }
    ]
}