bc(1)                                                 General Commands Manual                                                 bc(1)

       bc - An arbitrary precision calculator language

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

       bc  is  a language that supports arbitrary precision numbers with interactive execution of statements.  There are some simi‐
       larities in the syntax to the C programming language.  A standard math library is available by command line option.  If  re‐
       quested, 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.

       -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.

       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 results 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 example:
               .000001 has a length of 6 and scale of 6.
               1935.000 has a length of 7 and a scale of 3.

       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 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 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 pro‐
       cessed normally.

       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 encoun‐
       tered.  (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 extension.) Assigning a value outside this range to ibase will result in a value of 2 or  36.   Input
       numbers may contain the characters 0–9 and A–Z. (Note: They must be capitals.  Lower case letters are variable names.)  Sin‐
       gle digit numbers always have the value of the digit regardless of the value of ibase. (i.e. A = 10.)  For multi-digit  num‐
       bers,  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
       and an array variable is specified as
       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

       expr ^ expr
              The result of the expression is the value of the first raised to the second.  The second expression must be an  inte‐
              ger.   (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 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 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 rela‐
       tional 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 rela‐
       tional 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 expression.

       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 number 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  (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 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 state‐
       ment 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 state‐

              This statement does one of two things.  If the expression starts with "<variable> <assignment> ...", 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  assignment
              statement  and "(a=1)" is an expression that has an embedded assignment.  All numbers 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 separated by spaces.  Each digit contains the number of characters required to repre‐
              sent the base ten value of "obase-1".  Since numbers are of arbitrary 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 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 installations may allow the use of a  single  pe‐
              riod (.) 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 expres‐
              sions 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" (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 expres‐
              sion.  If the expression is non-zero, statement1 is executed.  If statement2 is present and the value of the  expres‐
              sion 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 statement.

       for ( [expression1] ; [expression2] ; [expression3] ) statement
              The  for  statement controls repeated execution of the statement.  Expression1 is evaluated before the loop.  Expres‐
              sion2 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 reevalua‐
              tion 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 ex‐
              pressions are an extension.  POSIX bc requires all three expressions.)  The following is equivalent code for the  for
              while (expression2) {

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

              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 processor to quit only when it is exe‐
              cuted.  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  parenthe‐
              sis are not required.

       These  statements  are  not  statements in the traditional sense.  They are not executed statements.  Their function is per‐
       formed 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.

              Print a longer warranty notice.  This is an extension.

       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 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 defi‐
       nition by the notation "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 parameters.  The named array is passed by value to the func‐
       tion.  Since function definitions are dynamic, parameter numbers and types are checked when a function is called.  Any  mis‐
       match in number or types of parameters will cause a runtime error.  A runtime error will also occur for the call to an unde‐
       fined 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  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 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 pa‐
       rameters 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  stan‐
       dard  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 be‐
       tween 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"; }
       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.

       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.

       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 bal‐
       ances.  This program is best kept in a file so that it can be used many times without having to retype it at every use.
              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

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

       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.  Set‐
       ting 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 manuals for the GNU readline,
       history and BSD libedit libraries.  One can not enable both readline and libedit at the same time.

       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 functionality and additions, where  new
       features are added.  The following is the list of differences and extensions.

       LANG environment
              This  version does not conform to the POSIX standard in the processing of the LANG environment variable and all envi‐
              ronment 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 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.

              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 def‐
              initions,  but  does  not provide a method to specify an array as an actual parameter.  (This is most likely an over‐
              sight 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 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 se‐
              quence 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.

              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 no‐
              tify 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 re‐
              moved during the clean up process.  During a non-interactive session, the SIGINT signal will terminate the entire run
              of bc.

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

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

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

              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.

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

              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.

       The following environment variables are processed by bc:

              This is the same as the -s option.

              This is another mechanism to get arguments to bc.  The format is the same as the command line arguments.  These argu‐
              ments are processed first, so any files listed in the environment arguments are processed before any command line ar‐
              gument 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  de‐
              fined every time bc is run.

              This should be an integer specifying the number of characters in an output line for numbers.  This includes the back‐
              slash 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.

       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.

       Error recovery is not very good yet.

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

       Philip A. Nelson

       The author would like to thank Steve Sommars (Steve.Sommars@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)