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bc(1)                                General Commands Manual                                bc(1)



NAME
       bc - An arbitrary precision calculator language

SYNTAX
       bc [ -hlwsqv ] [long-options] [  file ... ]

DESCRIPTION
       bc  is  a language that supports arbitrary precision numbers with interactive execution of
       statements.  There are some similarities in the syntax to the C programming  language.   A
       standard math library is available by command line option.  If requested, the math library
       is defined before processing any files.  bc starts by processing code from all  the  files
       listed  on  the command line in the order listed.  After all files have been processed, bc
       reads from the standard input.  All code is executed as it is read.  (If a file contains a
       command to halt the processor, bc will never read from the standard input.)

       This  version  of bc contains several extensions beyond traditional bc implementations and
       the POSIX draft standard.  Command line options can cause  these  extensions  to  print  a
       warning  or to be rejected.  This document describes the language accepted by this proces-
       sor.  Extensions will be identified as such.

   OPTIONS
       -h, --help
              Print the usage and exit.

       -i, --interactive
              Force interactive mode.

       -l, --mathlib
              Define the standard math library.

       -w, --warn
              Give warnings for extensions to POSIX bc.

       -s, --standard
              Process exactly the POSIX bc language.

       -q, --quiet
              Do not print the normal GNU bc welcome.

       -v, --version
              Print the version number and copyright and quit.

   NUMBERS
       The most basic element in bc is the number.   Numbers  are  arbitrary  precision  numbers.
       This  precision is both in the integer part and the fractional part.  All numbers are rep-
       resented internally in decimal and all computation is  done  in  decimal.   (This  version
       truncates  results from divide and multiply operations.)  There are two attributes of num-
       bers, the length and the scale.  The length is the total  number  of  significant  decimal
       digits  in  a number and the scale is the total number of decimal digits after the decimal
       point.  For example:
               .000001 has a length of 6 and scale of 6.
               1935.000 has a length of 7 and a scale of 3.

   VARIABLES
       Numbers are stored in two types of variables, simple variables and  arrays.   Both  simple
       variables and array variables are named.  Names begin with a letter followed by any number
       of letters, digits and underscores.  All letters must be lower case.  (Full  alpha-numeric
       names  are  an extension. In POSIX bc all names are a single lower case letter.)  The type
       of variable is clear by the context because all array variable names will be  followed  by
       brackets ([]).

       There  are  four special variables, scale, ibase, obase, and last.  scale defines how some
       operations use digits after the decimal point.  The default value of scale is 0. ibase and
       obase define the conversion base for input and output numbers.  The default for both input
       and output is base 10.  last (an extension) is a variable that has the value of  the  last
       printed  number.   These  will  be  discussed in further detail where appropriate.  All of
       these variables may have values assigned to them as well as used in expressions.

   COMMENTS
       Comments in bc start with the characters /* and end with the characters */.  Comments  may
       start  anywhere  and  appear  as  a  single  space in the input.  (This causes comments to
       delimit other input items.  For example, a comment can not be found in  the  middle  of  a
       variable name.)  Comments include any newlines (end of line) between the start and the end
       of the comment.

       To support the use of scripts for bc, a single line comment has been added  as  an  exten-
       sion.   A single line comment starts at a # character and continues to the next end of the
       line.  The end of line character is not part of the comment and is processed normally.

   EXPRESSIONS
       The numbers are manipulated  by  expressions  and  statements.   Since  the  language  was
       designed  to  be interactive, statements and expressions are executed as soon as possible.
       There is no "main" program.  Instead, code is executed as it is encountered.   (Functions,
       discussed in detail later, are defined when encountered.)

       A  simple  expression is just a constant. bc converts constants into internal decimal num-
       bers using the current input base, specified by the variable ibase. (There is an exception
       in  functions.)   The  legal  values of ibase are 2 through 16.  Assigning a value outside
       this range to ibase will result in a value of 2 or 16.   Input  numbers  may  contain  the
       characters  0-9  and  A-F.  (Note: They must be capitals.  Lower case letters are variable
       names.)  Single digit numbers always have the value of the digit regardless of  the  value
       of  ibase. (i.e. A = 10.)  For multi-digit numbers, bc changes all input digits greater or
       equal to ibase to the value of ibase-1.  This makes the number FFF always be the largest 3
       digit number of the input base.

       Full  expressions are similar to many other high level languages.  Since there is only one
       kind of number, there are no rules for mixing types.  Instead,  there  are  rules  on  the
       scale  of  expressions.   Every expression has a scale.  This is derived from the scale of
       original numbers, the operation performed and in many cases, the  value  of  the  variable
       scale. Legal values of the variable scale are 0 to the maximum number representable by a C
       integer.

       In the following descriptions of legal expressions, "expr" refers to a complete expression
       and "var" refers to a simple or an array variable.  A simple variable is just a
              name
       and an array variable is specified as
              name[expr]
       Unless  specifically mentioned the scale of the result is the maximum scale of the expres-
       sions involved.

       - expr The result is the negation of the expression.

       ++ var The variable is incremented by one and the new value is the result of  the  expres-
              sion.

       -- var The  variable  is decremented by one and the new value is the result of the expres-
              sion.

       var ++
               The result of the expression is the value of the variable and then the variable is
              incremented by one.

       var -- The  result of the expression is the value of the variable and then the variable is
              decremented by one.

       expr + expr
              The result of the expression is the sum of the two expressions.

       expr - expr
              The result of the expression is the difference of the two expressions.

       expr * expr
              The result of the expression is the product of the two expressions.

       expr / expr
              The result of the expression is the quotient of the two expressions.  The scale  of
              the result is the value of the variable scale.

       expr % expr
              The result of the expression is the "remainder" and it is computed in the following
              way.  To compute a%b, first a/b is computed to scale digits.  That result  is  used
              to  compute  a-(a/b)*b  to the scale of the maximum of scale+scale(b) and scale(a).
              If scale is set to zero and both expressions are integers this  expression  is  the
              integer remainder function.

       expr ^ expr
              The  result  of  the expression is the value of the first raised to the second. The
              second expression must be an integer.  (If the second expression is not an integer,
              a  warning  is  generated and the expression is truncated to get an integer value.)
              The scale of the result is scale if the exponent is negative.  If the  exponent  is
              positive  the  scale of the result is the minimum of the scale of the first expres-
              sion times the value of the exponent and the maximum of scale and the scale of  the
              first  expression.  (e.g. scale(a^b) = min(scale(a)*b, max( scale, scale(a))).)  It
              should be noted that expr^0 will always return the value of 1.

       ( expr )
              This alters the standard precedence to force the evaluation of the expression.

       var = expr
              The variable is assigned the value of the expression.

       var <op>= expr
              This is equivalent to "var = var <op> expr" with the exception that the "var"  part
              is evaluated only once.  This can make a difference if "var" is an array.

       Relational  expressions are a special kind of expression that always evaluate to 0 or 1, 0
       if the relation is false and 1 if the relation is true.  These may  appear  in  any  legal
       expression.   (POSIX  bc  requires that relational expressions are used only in if, while,
       and for statements and that only one relational test may be done in them.)  The relational
       operators are

       expr1 < expr2
              The result is 1 if expr1 is strictly less than expr2.

       expr1 <= expr2
              The result is 1 if expr1 is less than or equal to expr2.

       expr1 > expr2
              The result is 1 if expr1 is strictly greater than expr2.

       expr1 >= expr2
              The result is 1 if expr1 is greater than or equal to expr2.

       expr1 == expr2
              The result is 1 if expr1 is equal to expr2.

       expr1 != expr2
              The result is 1 if expr1 is not equal to expr2.

       Boolean  operations  are  also  legal.   (POSIX  bc does NOT have boolean operations). The
       result of all boolean operations are 0 and 1 (for false and true) as in relational expres-
       sions.  The boolean operators are:

       !expr  The result is 1 if expr is 0.

       expr && expr
              The result is 1 if both expressions are non-zero.

       expr || expr
              The result is 1 if either expression is non-zero.

       The expression precedence is as follows: (lowest to highest)
              || operator, left associative
              && operator, left associative
              ! operator, nonassociative
              Relational operators, left associative
              Assignment operator, right associative
              + and - operators, left associative
              *, / and % operators, left associative
              ^ operator, right associative
              unary - operator, nonassociative
              ++ and -- operators, nonassociative

       This  precedence  was  chosen so that POSIX compliant bc programs will run correctly. This
       will cause the use of the relational and logical operators to have some  unusual  behavior
       when used with assignment expressions.  Consider the expression:
              a = 3 < 5

       Most  C  programmers would assume this would assign the result of "3 < 5" (the value 1) to
       the variable "a".  What this does in bc is assign the value 3 to the variable "a" and then
       compare 3 to 5.  It is best to use parenthesis when using relational and logical operators
       with the assignment operators.

       There are a few more special expressions that are provided in bc.  These have to  do  with
       user  defined  functions  and  standard functions.  They all appear as "name(parameters)".
       See the section on functions for user defined functions.  The standard functions are:

       length ( expression )
              The value of the length function is the number of significant digits in the expres-
              sion.

       read ( )
              The  read  function  (an  extension)  will  read  a number from the standard input,
              regardless of where the function occurs.   Beware, this can cause problems with the
              mixing  of  data and program in the standard input.  The best use for this function
              is in a previously written program that needs input from the user, but never allows
              program code to be input from the user.  The value of the read function is the num-
              ber read from the standard input using the current value of the variable ibase  for
              the conversion base.

       scale ( expression )
              The  value of the scale function is the number of digits after the decimal point in
              the expression.

       sqrt ( expression )
              The value of the sqrt function is the  square  root  of  the  expression.   If  the
              expression is negative, a run time error is generated.

   STATEMENTS
       Statements  (as  in most algebraic languages) provide the sequencing of expression evalua-
       tion.  In bc statements are executed "as soon as possible."  Execution happens when a new-
       line  in  encountered and there is one or more complete statements.  Due to this immediate
       execution, newlines are very important in bc. In fact, both a semicolon and a newline  are
       used  as  statement  separators.   An improperly placed newline will cause a syntax error.
       Because newlines are statement separators, it is possible to hide a newline by  using  the
       backslash  character.   The  sequence  "\<nl>", where <nl> is the newline appears to bc as
       whitespace instead of a newline.  A statement list is a series of statements separated  by
       semicolons  and  newlines.   The  following  is  a list of bc statements and what they do:
       (Things enclosed in brackets ([]) are optional parts of the statement.)

       expression
              This statement does one of two things.  If the expression starts  with  "<variable>
              <assignment>  ...", it is considered to be an assignment statement.  If the expres-
              sion is not an assignment statement, the expression is evaluated and printed to the
              output.   After the number is printed, a newline is printed.  For example, "a=1" is
              an assignment statement and "(a=1)" is an expression that has an  embedded  assign-
              ment.   All numbers that are printed are printed in the base specified by the vari-
              able obase. The legal values for obase are 2 through BC_BASE_MAX.  (See the section
              LIMITS.)  For bases 2 through 16, the usual method of writing numbers is used.  For
              bases greater than 16, bc uses a multi-character digit method of printing the  num-
              bers  where each higher base digit is printed as a base 10 number.  The multi-char-
              acter digits are separated by spaces.  Each digit contains the number of characters
              required  to represent the base ten value of "obase-1".  Since numbers are of arbi-
              trary precision, some numbers may not be printable on a single output line.   These
              long  numbers  will  be split across lines using the "\" as the last character on a
              line.  The maximum number of characters printed per line is 70.  Due to the  inter-
              active  nature  of  bc,  printing  a number causes the side effect of assigning the
              printed value to the special variable last. This allows the  user  to  recover  the
              last value printed without having to retype the expression that printed the number.
              Assigning to last is legal and will overwrite  the  last  printed  value  with  the
              assigned  value.   The  newly  assigned  value will remain until the next number is
              printed or another value is assigned to last.  (Some installations  may  allow  the
              use  of  a single period (.) which is not part of a number as a short hand notation
              for for last.)

       string The string is printed to the output.  Strings start with a double  quote  character
              and  contain  all characters until the next double quote character.  All characters
              are take literally, including any newline.  No newline character is  printed  after
              the string.

       print list
              The  print  statement (an extension) provides another method of output.  The "list"
              is a list of strings and expressions separated by commas.  Each string  or  expres-
              sion  is  printed  in  the  order  of the list.  No terminating newline is printed.
              Expressions are evaluated and their value is printed and assigned to  the  variable
              last. Strings in the print statement are printed to the output and may contain spe-
              cial characters.  Special characters start with the backslash character  (\).   The
              special  characters  recognized by bc are "a" (alert or bell), "b" (backspace), "f"
              (form feed), "n" (newline), "r" (carriage return), "q" (double quote),  "t"  (tab),
              and "\" (backslash).  Any other character following the backslash will be ignored.

       { statement_list }
              This  is  the  compound  statement.   It  allows  multiple statements to be grouped
              together for execution.

       if ( expression ) statement1 [else statement2]
              The if statement evaluates the expression and  executes  statement1  or  statement2
              depending  on  the  value of the expression.  If the expression is non-zero, state-
              ment1 is executed.  If statement2 is present and the value of the expression is  0,
              then statement2 is executed.  (The else clause is an extension.)

       while ( expression ) statement
              The  while  statement  will execute the statement while the expression is non-zero.
              It evaluates the expression before each execution of the  statement.    Termination
              of the loop is caused by a zero expression value or the execution of a break state-
              ment.

       for ( [expression1] ; [expression2] ; [expression3] ) statement
              The for statement controls repeated execution of  the  statement.   Expression1  is
              evaluated  before  the loop.  Expression2 is evaluated before each execution of the
              statement.  If it is non-zero, the statement is evaluated.  If it is zero, the loop
              is  terminated.   After  each  execution of the statement, expression3 is evaluated
              before the reevaluation of expression2.  If expression1 or expression3 are missing,
              nothing is evaluated at the point they would be evaluated.  If expression2 is miss-
              ing, it is the same as substituting the value 1  for  expression2.   (The  optional
              expressions  are  an extension. POSIX bc requires all three expressions.)  The fol-
              lowing is equivalent code for the for statement:
              expression1;
              while (expression2) {
                 statement;
                 expression3;
              }

       break  This statement causes a forced exit of the most recent enclosing while statement or
              for statement.

       continue
              The  continue statement (an extension)  causes the most recent enclosing for state-
              ment to start the next iteration.

       halt   The halt statement (an extension) is an executed statement that causes the bc  pro-
              cessor  to quit only when it is executed.  For example, "if (0 == 1) halt" will not
              cause bc to terminate because the halt is not executed.

       return Return the value 0 from a function.  (See the section on functions.)

       return ( expression )
              Return the value of the expression from a function.   (See  the  section  on  func-
              tions.)  As an extension, the parenthesis are not required.

   PSEUDO STATEMENTS
       These  statements  are  not  statements  in  the traditional sense.  They are not executed
       statements.  Their function is performed at "compile" time.

       limits Print the local limits enforced by the local version of bc.  This is an extension.

       quit   When the quit statement is read, the bc  processor  is  terminated,  regardless  of
              where  the  quit statement is found.  For example, "if (0 == 1) quit" will cause bc
              to terminate.

       warranty
              Print a longer warranty notice.  This is an extension.

   FUNCTIONS
       Functions provide a method of defining a computation that can be  executed  later.   Func-
       tions  in bc always compute a value and return it to the caller.  Function definitions are
       "dynamic" in the sense that a function is undefined until a definition is  encountered  in
       the  input.   That  definition is then used until another definition function for the same
       name is encountered.  The new definition then replaces the older definition.   A  function
       is defined as follows:
              define name ( parameters ) { newline
                  auto_list   statement_list }
       A function call is just an expression of the form "name(parameters)".

       Parameters are numbers or arrays (an extension).  In the function definition, zero or more
       parameters are defined by listing their names separated by  commas.   All  parameters  are
       call  by  value parameters.  Arrays are specified in the parameter definition by the nota-
       tion "name[]".   In the function call, actual parameters are full expressions  for  number
       parameters.   The  same  notation is used for passing arrays as for defining array parame-
       ters.  The named array is passed by value to the function.  Since function definitions are
       dynamic,  parameter numbers and types are checked when a function is called.  Any mismatch
       in number or types of parameters will cause a runtime error.  A runtime  error  will  also
       occur for the call to an undefined function.

       The  auto_list  is  an optional list of variables that are for "local" use.  The syntax of
       the auto list (if present) is "auto name, ... ;".  (The semicolon is optional.)  Each name
       is  the  name  of an auto variable.  Arrays may be specified by using the same notation as
       used in parameters.  These variables have their values pushed onto a stack at the start of
       the  function.   The variables are then initialized to zero and used throughout the execu-
       tion of the function.  At function exit, these variables are popped so that  the  original
       value  (at the time of the function call) of these variables are restored.  The parameters
       are really auto variables that are initialized to a value provided in the  function  call.
       Auto  variables are different than traditional local variables because if function A calls
       function B, B may access function A's auto variables by just using the same  name,  unless
       function B has called them auto variables.  Due to the fact that auto variables and param-
       eters are pushed onto a stack, bc supports recursive functions.

       The function body is a list of bc statements.  Again, statements are  separated  by  semi-
       colons  or newlines.  Return statements cause the termination of a function and the return
       of a value.  There are two versions of the return statement.  The  first  form,  "return",
       returns  the value 0 to the calling expression.  The second form, "return ( expression )",
       computes the value of the expression and returns that value  to  the  calling  expression.
       There  is an implied "return (0)" at the end of every function.  This allows a function to
       terminate and return 0 without an explicit return statement.

       Functions also change the usage of the variable ibase.  All constants in the function body
       will  be  converted using the value of ibase at the time of the function call.  Changes of
       ibase will be ignored during the execution of the function except for the  standard  func-
       tion read, which will always use the current value of ibase for conversion of numbers.

       Several  extensions have been added to functions.  First, the format of the definition has
       been slightly relaxed.  The standard requires the opening brace be on the same line as the
       define  keyword  and  all other parts must be on following lines.  This version of bc will
       allow any number of newlines before and after the opening  brace  of  the  function.   For
       example, the following definitions are legal.
              define d (n) { return (2*n); }
              define d (n)
                { return (2*n); }

       Functions  may  be  defined  as void.  A void funtion returns no value and thus may not be
       used in any place that needs a value.  A void function does not produce  any  output  when
       called  by  itself  on  an  input  line.  The key word void is placed between the key word
       define and the function name.  For example, consider the following session.
              define py (y) { print "--->", y, "<---", "0; }
              define void px (x) { print "--->", x, "<---", "0; }
              py(1)
              --->1<---
              0
              px(1)
              --->1<---
       Since py is not a void function, the call of py(1) prints  the  desired  output  and  then
       prints  a  second  line  that is the value of the function.  Since the value of a function
       that is not given an explicit return statement is zero, the zero is printed.   For  px(1),
       no zero is printed because the function is a void function.

       Also,  call  by  variable  for arrays was added.  To declare a call by variable array, the
       declaration of the array parameter in the function definition looks like  "*name[]".   The
       call to the function remains the same as call by value arrays.

   MATH LIBRARY
       If  bc is invoked with the -l option, a math library is preloaded and the default scale is
       set to 20.   The math functions will calculate their results to the scale set at the  time
       of their call.  The math library defines the following functions:

       s (x)  The sine of x, x is in radians.

       c (x)  The cosine of x, x is in radians.

       a (x)  The arctangent of x, arctangent returns radians.

       l (x)  The natural logarithm of x.

       e (x)  The exponential function of raising e to the value x.

       j (n,x)
              The Bessel function of integer order n of x.

   EXAMPLES
       In /bin/sh,  the following will assign the value of "pi" to the shell variable pi.
               pi=$(echo "scale=10; 4*a(1)" | bc -l)

       The  following  is  the  definition  of the exponential function used in the math library.
       This function is written in POSIX bc.
              scale = 20

              /* Uses the fact that e^x = (e^(x/2))^2
                 When x is small enough, we use the series:
                   e^x = 1 + x + x^2/2! + x^3/3! + ...
              */

              define e(x) {
                auto  a, d, e, f, i, m, v, z

                /* Check the sign of x. */
                if (x<0) {
                  m = 1
                  x = -x
                }

                /* Precondition x. */
                z = scale;
                scale = 4 + z + .44*x;
                while (x > 1) {
                  f += 1;
                  x /= 2;
                }

                /* Initialize the variables. */
                v = 1+x
                a = x
                d = 1

                for (i=2; 1; i++) {
                  e = (a *= x) / (d *= i)
                  if (e == 0) {
                    if (f>0) while (f--)  v = v*v;
                    scale = z
                    if (m) return (1/v);
                    return (v/1);
                  }
                  v += e
                }
              }

       The following is code that uses the extended features of bc to implement a simple  program
       for calculating checkbook balances.  This program is best kept in a file so that it can be
       used many times without having to retype it at every use.
              scale=2
              print "\nCheck book program!\n"
              print "  Remember, deposits are negative transactions.\n"
              print "  Exit by a 0 transaction.\n\n"

              print "Initial balance? "; bal = read()
              bal /= 1
              print "\n"
              while (1) {
                "current balance = "; bal
                "transaction? "; trans = read()
                if (trans == 0) break;
                bal -= trans
                bal /= 1
              }
              quit

       The following is the definition of the recursive factorial function.
              define f (x) {
                if (x <= 1) return (1);
                return (f(x-1) * x);
              }

   READLINE AND LIBEDIT OPTIONS
       GNU bc can be compiled (via a configure option) to  use  the  GNU  readline  input  editor
       library  or  the  BSD libedit library.  This allows the user to do editing of lines before
       sending them to bc.  It also allows for a history of  previous  lines  typed.   When  this
       option  is  selected, bc has one more special variable.  This special variable, history is
       the number of lines of history retained.  For readline, a value of -1 means that an unlim-
       ited  number  of  history  lines are retained.  Setting the value of history to a positive
       number restricts the number of history lines to the number given.  The value of 0 disables
       the  history feature.  The default value is 100. For more information, read the user manu-
       als for the GNU readline, history and BSD libedit libraries.   One  can  not  enable  both
       readline and libedit at the same time.

   DIFFERENCES
       This  version  of bc was implemented from the POSIX P1003.2/D11 draft and contains several
       differences and extensions relative to the draft and traditional implementations.   It  is
       not  implemented  in  the  traditional  way using dc(1).  This version is a single process
       which parses and runs a byte code translation of the program.  There is an  "undocumented"
       option (-c) that causes the program to output the byte code to the standard output instead
       of running it.  It was mainly used  for  debugging  the  parser  and  preparing  the  math
       library.

       A major source of differences is extensions, where a feature is extended to add more func-
       tionality and additions, where new features are added.  The following is the list of  dif-
       ferences and extensions.

       LANG environment
              This  version  does not conform to the POSIX standard in the processing of the LANG
              environment variable and all environment variables starting with LC_.

       names  Traditional and POSIX bc have single letter  names  for  functions,  variables  and
              arrays.  They have been extended to be multi-character names that start with a let-
              ter and may contain letters, numbers and the underscore character.

       Strings
              Strings are not allowed to contain NUL characters.  POSIX says all characters  must
              be included in strings.

       last   POSIX  bc does not have a last variable.  Some implementations of bc use the period
              (.) in a similar way.

       comparisons
              POSIX bc allows comparisons only in the if statement, the while statement, and  the
              second  expression  of  the  for statement.  Also, only one relational operation is
              allowed in each of those statements.

       if statement, else clause
              POSIX bc does not have an else clause.

       for statement
              POSIX bc requires all expressions to be present in the for statement.

       &&, ||, !
              POSIX bc does not have the logical operators.

       read function
              POSIX bc does not have a read function.

       print statement
              POSIX bc does not have a print statement .

       continue statement
              POSIX bc does not have a continue statement.

       return statement
              POSIX bc requires parentheses around the return expression.

       array parameters
              POSIX bc does not (currently) support array parameters in full.  The POSIX  grammar
              allows for arrays in function definitions, but does not provide a method to specify
              an array as an actual parameter.  (This is most likely an oversight  in  the  gram-
              mar.)  Traditional implementations of bc have only call by value array parameters.

       function format
              POSIX bc requires the opening brace on the same line as the define key word and the
              auto statement on the next line.

       =+, =-, =*, =/, =%, =^
              POSIX bc does not require these "old style" assignment  operators  to  be  defined.
              This  version may allow these "old style" assignments.  Use the limits statement to
              see if the installed version supports them.  If it does  support  the  "old  style"
              assignment  operators, the statement "a =- 1" will decrement a by 1 instead of set-
              ting a to the value -1.

       spaces in numbers
              Other implementations of bc allow spaces in numbers.  For example,  "x=1  3"  would
              assign  the  value  13  to the variable x.  The same statement would cause a syntax
              error in this version of bc.

       errors and execution
              This implementation varies from other implementations in terms of what code will be
              executed  when syntax and other errors are found in the program.  If a syntax error
              is found in a function definition, error recovery tries to find the beginning of  a
              statement  and continue to parse the function.  Once a syntax error is found in the
              function, the function will not be callable and becomes undefined.   Syntax  errors
              in the interactive execution code will invalidate the current execution block.  The
              execution block is terminated by an end of  line  that  appears  after  a  complete
              sequence of statements.  For example,
              a = 1
              b = 2
       has two execution blocks and
              { a = 1
                b = 2 }
       has  one  execution  block.  Any runtime error will terminate the execution of the current
       execution block.  A runtime warning will not terminate the current execution block.

       Interrupts
              During an interactive session, the SIGINT signal (usually generated by the control-
              C  character from the terminal) will cause execution of the current execution block
              to be interrupted.  It will display a "runtime" error indicating which function was
              interrupted.   After all runtime structures have been cleaned up, a message will be
              printed to notify the user that bc is ready for more input.  All previously defined
              functions  remain  defined and the value of all non-auto variables are the value at
              the point of interruption.  All auto variables and function parameters are  removed
              during  the  clean up process.  During a non-interactive session, the SIGINT signal
              will terminate the entire run of bc.

   LIMITS
       The following are the limits currently in place for this bc processor.  Some of  them  may
       have been changed by an installation.  Use the limits statement to see the actual values.

       BC_BASE_MAX
              The maximum output base is currently set at 999.  The maximum input base is 16.

       BC_DIM_MAX
              This  is  currently  an arbitrary limit of 65535 as distributed.  Your installation
              may be different.

       BC_SCALE_MAX
              The number of digits after the decimal point is limited to INT_MAX  digits.   Also,
              the number of digits before the decimal point is limited to INT_MAX digits.

       BC_STRING_MAX
              The limit on the number of characters in a string is INT_MAX characters.

       exponent
              The value of the exponent in the raise operation (^) is limited to LONG_MAX.

       variable names
              The  current  limit on the number of unique names is 32767 for each of simple vari-
              ables, arrays and functions.

ENVIRONMENT VARIABLES
       The following environment variables are processed by bc:

       POSIXLY_CORRECT
              This is the same as the -s option.

       BC_ENV_ARGS
              This is another mechanism to get arguments to bc.  The format is the  same  as  the
              command  line  arguments.  These arguments are processed first, so any files listed
              in the environment arguments are processed before any command line argument  files.
              This  allows  the  user  to  set up "standard" options and files to be processed at
              every invocation of bc.  The files in the  environment  variables  would  typically
              contain  function definitions for functions the user wants defined every time bc is
              run.

       BC_LINE_LENGTH
              This should be an integer specifying the number of characters in an output line for
              numbers.  This  includes the backslash and newline characters for long numbers.  As
              an extension, the value of zero disables the multi-line feature.  Any  other  value
              of this variable that is less than 3 sets the line length to 70.

DIAGNOSTICS
       If  any  file  on  the  command  line  can  not be opened, bc will report that the file is
       unavailable and terminate.  Also, there are compile and run time diagnostics  that  should
       be self-explanatory.

BUGS
       Error recovery is not very good yet.

       Email  bug reports to bug-bc AT gnu.org.  Be sure to include the word ``bc'' somewhere in the
       ``Subject:'' field.

AUTHOR
       Philip A. Nelson
       philnelson AT acm.org

ACKNOWLEDGEMENTS
       The author would like to thank Steve Sommars  (Steve.Sommars AT att.com)  for  his  extensive
       help  in  testing  the implementation.  Many great suggestions were given.  This is a much
       better product due to his involvement.



GNU Project                                 2006-06-11                                      bc(1)

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