man > bc(1)

TLDR: bc (tldr-pages)

An arbitrary precision calculator language.

  • Start an interactive session
    bc
  • Start an interactive session with the standard math library enabled
    bc {{-i|--interactive}} {{-l|--mathlib}}
  • Calculate an expression
    echo '{{5 / 3}}' | bc
  • Execute a script
    bc {{path/to/script.bc}}
  • Calculate an expression with the specified scale
    echo 'scale = {{10}}; {{5 / 3}}' | bc
  • Calculate a sine/cosine/arctangent/natural logarithm/exponential function using `mathlib`
    echo '{{s|c|a|l|e}}({{1}})' | bc {{-l|--mathlib}}
  • Execute an inline factorial script
    echo "define factorial(n) { if (n <= 1) return 1; return n*factorial(n-1); }; factorial({{10}})" | bc
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 processor.  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 represented
       internally in decimal and all computation is done in decimal.  (This  version  truncates  re‐
       sults  from divide and multiply operations.)  There are two attributes of numbers, the length
       and the scale.  The length is the total number of decimal digits used by bc  to  represent  a
       number  and the scale is the total number of decimal digits after the decimal point.  For ex‐
       ample:
               .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 vari‐
       ables 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  vari‐
       able  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  op‐
       erations  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 com‐
       ment.

       To support the use of scripts for bc, a single line comment has been added as  an  extension.
       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  numbers
       using  the  current  input  base,  specified by the variable ibase. (There is an exception in
       functions.)  The legal values of ibase are 2 through 36. (Bases greater than 16 are an exten‐
       sion.) Assigning a value outside this range to ibase will result in a value of 2 or 36.   In‐
       put numbers may contain the characters 0–9 and A–Z. (Note: They must be capitals.  Lower case
       letters are variable names.)  Single digit numbers always have the value of the digit regard‐
       less  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  ZZZ  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 expressions
       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 expression.

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

       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 sec‐
              ond 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 expression 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 expres‐
       sion.  (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 expressions.  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  com‐
       pare  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,  regard‐
              less  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  number  read
              from  the standard input using the current value of the variable ibase for the conver‐
              sion 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  expres‐
              sion is negative, a run time error is generated.

   STATEMENTS
       Statements  (as in most algebraic languages) provide the sequencing of expression evaluation.
       In bc statements are executed "as soon as possible."  Execution happens when a newline in en‐
       countered 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  new‐
       lines are statement separators, it is possible to hide a newline by using the backslash char‐
       acter.   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  new‐
       lines.  The following is a list of bc statements and what they do: (Things enclosed in brack‐
       ets ([]) are optional parts of the statement.)

       expression
              This statement does one of two things.  If the expression starts with "<variable> <as‐
              signment>  ...", it is considered to be an assignment statement.  If the expression 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 assign‐
              ment statement and "(a=1)" is an expression that has an embedded assignment.  All num‐
              bers that are printed are printed in the base specified by the  variable  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 numbers where each
              higher base digit is printed as a base 10 number.  The multi-character digits are sep‐
              arated by spaces.  Each digit contains the number of characters required to  represent
              the  base ten value of "obase-1".  Since numbers are of arbitrary precision, some num‐
              bers 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 interactive 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 instal‐
              lations 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  expression  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  special  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"  (new‐
              line), "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  de‐
              pending  on the value of the expression.  If the expression is non-zero, statement1 is
              executed.  If statement2 is present and the value of the expression is 0, then  state‐
              ment2 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 statement.

       for ( [expression1] ; [expression2] ; [expression3] ) statement
              The for statement controls repeated execution of the statement.  Expression1 is evalu‐
              ated  before  the  loop.  Expression2 is evaluated before each execution of the state‐
              ment.  If it is non-zero, the statement is evaluated.  If it is zero, the loop is ter‐
              minated.  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 missing, it is  the
              same  as  substituting  the value 1 for expression2.  (The optional expressions are an
              extension.  POSIX bc requires all three expressions.)   The  following  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  statement
              to start the next iteration.

       halt   The  halt statement (an extension) is an executed statement that causes the bc proces‐
              sor 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 functions.)
              As an extension, the parenthesis are not required.

   PSEUDO STATEMENTS
       These statements are not statements in the traditional sense.  They are not  executed  state‐
       ments.  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  termi‐
              nate.

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

   FUNCTIONS
       Functions  provide  a method of defining a computation that can be executed later.  Functions
       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 encoun‐
       tered.  The new definition then replaces the older definition.  A function is defined as fol‐
       lows:
              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  notation
       "name[]".    In  the function call, actual parameters are full expressions for number parame‐
       ters.  The same notation is used for passing arrays as for defining  array  parameters.   The
       named  array is passed by value to the function.  Since function definitions are dynamic, pa‐
       rameter 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  pa‐
       rameters.   These  variables  have their values pushed onto a stack at the start of the func‐
       tion.  The variables are then initialized to zero and used throughout the  execution  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  ac‐
       cess  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 parameters are  pushed  onto  a
       stack, bc supports recursive functions.

       The  function body is a list of bc statements.  Again, statements are separated by semicolons
       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 function
       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 function 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, "<---", "\n"; }
              define void px (x) { print "--->", x, "<---", "\n"; }
              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 decla‐
       ration  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 unlimited 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 de‐
       fault value is 100.  For more information, read the user manuals for the GNU  readline,  his‐
       tory  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 dif‐
       ferences and extensions relative to the draft and traditional implementations.  It is not im‐
       plemented 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 differ‐
       ences and extensions.

       LANG environment
              This version does not conform to the POSIX standard in the processing of the LANG  en‐
              vironment 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 letter 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  al‐
              lowed 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 al‐
              lows  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  grammar.)
              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 setting a to the
              value -1.

       spaces in numbers
              Other implementations of bc allow spaces in numbers.  For example, "x=1 3"  would  as‐
              sign 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 state‐
              ment  and  continue  to parse the function.  Once a syntax error is found in the func‐
              tion, 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 state‐
              ments.  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 exe‐
       cution 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 inter‐
              rupted.  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 variables,
              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  com‐
              mand  line arguments.  These arguments are processed first, so any files listed in the
              environment arguments are processed before any command line argument files.  This  al‐
              lows  the user to set up "standard" options and files to be processed at every invoca‐
              tion 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 unavail‐
       able and terminate.  Also, there are compile and run time diagnostics that should be self-ex‐
       planatory.

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)
bc(1)
NAME SYNTAX DESCRIPTION
-h, --help -i, --interactive -l, --mathlib -w, --warn -s, --standard -q, --quiet -v, --version continue warranty
ENVIRONMENT VARIABLES DIAGNOSTICS BUGS AUTHOR ACKNOWLEDGEMENTS

Generated by phpman v4.10.0-7-g98e9fd5 · Markdown · JSON · MCP Author: Che Dong Under GNU General Public License
2026-09-04 18:40 @216.73.216.150
CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
Valid XHTML 1.0 Transitional!Valid CSS!

^_top_^