Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
bc(1)			    General Commands Manual			 bc(1)

       bc - An arbitrary precision calculator language

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

       This man	page documents GNU bc version 1.06.

       bc  is a	language that supports arbitrary precision numbers with	inter-
       active 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 doc-
       ument 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 pre-
       cision 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 num-
       bers, the length	and the	scale.	The length is the total	number of sig-
       nificant	 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.

       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 exam-
       ple, 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 processed 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 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 numbers may contain the
       characters 0-9 and A-F. (Note: They must	be capitals.  Lower case  let-
       ters  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	repre-
       sentable	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

       expr * expr
	      The  result  of the expression is	the product of the two expres-

       expr / expr
	      The result of the	expression is the quotient of the two  expres-
	      sions.   The  scale  of  the result is the value of the variable

       expr % expr
	      The result of the	expression is the "remainder" and it  is  com-
	      puted  in	 the following way.  To	compute	a%b, first a/b is com-
	      puted 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 expo-
	      nent and the maximum of scale and	the scale of the first expres-
	      sion.    (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	state-
       ments 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

       !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	opera-
       tors to have some unusual behavior when used  with  assignment  expres-
       sions.  Consider	the expression:
	      a	= 3 < 5

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

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

       length (	expression )
	      The value	of the length function is the  number  of  significant
	      digits in	the 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 pro-
	      gram 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 con-
	      version 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 expres-
	      sion.  If	the expression is negative, a run time error is	gener-

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

	      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 out-
	      put.  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 represent the base
	      ten  value  of "obase-1".	 Since numbers are of arbitrary	preci-
	      sion, 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 num-
	      ber 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  dou-
	      ble  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 sepa-
	      rated by commas.	Each string or expression is  printed  in  the
	      order  of	the list.  No terminating newline is printed.  Expres-
	      sions 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  charac-
	      ters  start with the backslash character (\).  The special char-
	      acters  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	state-
	      ment1  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 expres-
	      sion  is non-zero.  It evaluates the expression before each exe-
	      cution 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.	 Expression2 is	evalu-
	      ated before each execution of the	statement.  If it is non-zero,
	      the statement is evaluated.  If it is zero, the loop  is	termi-
	      nated.   After  each  execution of the statement,	expression3 is
	      evaluated	before the reevaluation	of  expression2.   If  expres-
	      sion1  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:
	      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	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 func-

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

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

       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 exe-
       cuted 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 defi-
       nition, zero or more parameters are defined by listing their names sep-
       arated  by  commas.  Numbers are	only call by value parameters.	Arrays
       are only	call by	variable.  Arrays are specified	in the parameter defi-
       nition by the notation "name[]".	  In the function call,	actual parame-
       ters 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 variable to the function.   Since  function  defini-
       tions are dynamic, parameter numbers and	types are checked when a func-
       tion 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	 vari-
       able.   Arrays  may  be specified by using the same notation as used in
       parameters.  These variables have their values pushed onto a  stack  at
       the  start of the function.  The	variables are then initialized to zero
       and used	throughout the 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
       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 ter-
       mination	of a function and the return of	a value.  There	are  two  ver-
       sions  of  the return statement.	 The first form, "return", returns the
       value 0 to the calling expression.  The second form, "return (  expres-
       sion )",	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 with-
       out 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.

       As an extension,	 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  defini-
       tions are legal.
	      define d (n) { return (2*n); }
	      define d (n)
		{ return (2*n);	}

       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	imple-
       ment 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.
	      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 num-
       ber 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 fea-
       ture.  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  "undocu-
       mented"	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   This  version does not conform to	the POSIX standard in the pro-
	      cessing 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-char-
	      acter  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

       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

       &&, ||, !
	      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

       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" assign-
	      ments.  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 exam-
	      ple, "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 interac-
	      tive 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	execu-
       tion of the current execution block.  A runtime warning will not	termi-
       nate the	current	execution block.

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

	      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 arguments are
	      processed	first, so any files listed in the environent 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 environ-
	      ment variables would typically contain function definitions  for
	      functions	the user wants defined every time bc is	run.

	      This  should be an integer specifing the number of characters in
	      an output	line for numbers. This includes	the backslash and new-
	      line characters for long numbers.

       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	  Be  sure to include the word
       ``bc'' somewhere	in the ``Subject:'' field.

       Philip A. Nelson

       The author would	like to	thank  Steve  Sommars  (
       for  his	extensive help in testing the implementation.  Many great sug-
       gestions	were given.  This is a much better product due to his involve-

				       .				 bc(1)


Want to link to this manual page? Use this URL:

home | help