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bc(1)                                                                    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  stan-
       dard.   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 compu-
       tation 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 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 fol-
       lowed 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 extension.  A single line com-
       ment 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 16.  Assigning a value outside this range to ibase will result in a value of 2 or 16.  Input num-
       bers 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 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 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  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 rela-
       tional 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.  Con-
       sider 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 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
       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 semi-
       colon  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 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  assign-
              ment.   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 rep-
              resent 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 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  char-
              acters 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  recog-
              nized  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  back-
              slash 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, statement1 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 expres-
              sion 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.  Expression2 is evaluated before each execution of the statement.  If it is non-zero,  the  state-
              ment  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 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  processor  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 statements.  Their func-
       tion 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.  Functions in bc always com-
       pute 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 defini-
       tion 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 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 function.  Since function definitions are dynamic,
       parameter numbers and types are checked when a function is called.  Any mismatch in number or types of  parame-
       ters 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 through-
       out 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 parame-
       ters 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  execu-
       tion  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 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 vari-
       able, 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 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.

   DIFFERENCES
       This version of bc was implemented from the POSIX P1003.2/D11 draft and contains several differences and exten-
       sions  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  addi-
       tions, 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 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 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 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 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  previ-
              ously  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  pro-
              cess.  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 func-
              tions.

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 dis-
              ables 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-bcATgnu.org.  Be sure to include the word ''bc'' somewhere in the ''Subject:'' field.

AUTHOR
       Philip A. Nelson
       philnelsonATacm.org

ACKNOWLEDGEMENTS
       The author would like to thank Steve Sommars (Steve.SommarsATatt.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)