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bc(1)			    General Commands Manual			 bc(1)

NAME
       bc - An arbitrary precision calculator language

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

VERSION
       This man	page documents GNU bc version 1.04.

DESCRIPTION
       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.

   OPTIONS
       -l     Define the standard math library.

       -w     Give warnings for	extensions to POSIX bc.

       -s     Process exactly the POSIX	bc language.

       -q     Do not print the normal GNU bc welcome.

       -v     Print the	version	number and copyright and quit.

       --mathlib
	      Define the standard math library.

       --warn Give warnings for	extensions to POSIX bc.

       --standard
	      Process exactly the POSIX	bc language.

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

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

   NUMBERS
       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.

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

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

   COMMENTS
       Comments	in bc start with the characters	/* and end with	the characters
       */.  Comments may start anywhere	and appear as a	single	space  in  the
       input.	(This causes comments to delimit other input items.  For 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.

   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 in-
       ternal 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
	      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  re-
	      sult of the expression.

       -- var The  variable is decremented by one and the new value is the re-
	      sult 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  ex-
	      pressions.

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

       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
	      scale.

       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  ex-
	      pression 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 ex-
	      ponent 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	state-
       ments  and that only one	relational test	may be done in them.)  The re-
       lational	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 op-
       erations).  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	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  as-
       signment	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.	   Be-
	      ware,  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-
	      ated.

   STATEMENTS
       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 se-
       quence "\<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.)

       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 out-
	      put.  After the number is	printed, a newline  is	printed.   For
	      example,	"a=1" is an assignment statement and "(a=1)" is	an ex-
	      pression 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 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	cause the side effect of assigning the printed
	      value  to	the special variable last. This	allows the user	to re-
	      cover the	last value printed without having to  retype  the  ex-
	      pression	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  in-
	      stallations  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,  in-
	      cluding  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 re-
	      turn), "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 op-
	      tional 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  be-
	      cause the	halt is	not executed.

       return Return  the  value 0 from	a function.  (See the section on func-
	      tions.)

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

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

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

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

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

   FUNCTIONS
       Functions provide a method of defining a	computation that can  be  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 in the	fact that if function A	calls function B, B may	access
       function	 A's  auto variables by	just using the same name, unless func-
       tion B has called them auto variables.  Due to the fact that auto vari-
       ables  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.

   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 li-
       brary 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	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.
	      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 OPTION
       GNU bc can be compiled (via a configure option) to use the GNU readline
       input editor library.  This allows the user to do more 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.  A value of -1	means that an unlimited	number of his-
       tory lines are retained.	 This is the default value.  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.  For
       more  information,  read	the user manuals for the GNU readline and his-
       tory libraries.

   DIFFERENCES
       This version of bc was implemented from the POSIX P1003.2/D11 draft and
       contains	 several  differences and extensions relative to the draft and
       traditional implementations.  It	is not implemented in the  traditional
       way  using  dc(1).   This  version is a single process which parses and
       runs a byte code	translation of the  program.   There  is  an  "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  de-
       bugging the parser and preparing	the math library.

       A  major	 source	 of  differences is extensions,	where a	feature	is ex-
       tended 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
	      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.

       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  pa-
	      rameter.	 (This	is  most  likely an oversight in the grammar.)
	      Traditional implementations of bc	have only call by value	 array
	      parameters.

       =+, =-, =*, =/, =%, =^
	      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 er-
	      ror  is found in the function, the function will not be callable
	      and becomes undefined.  Syntax errors in the interactive	execu-
	      tion code	will invalidate	the current execution block.  The exe-
	      cution 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.

       Interrupts
	      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 in-
	      terrupted.  After	all runtime structures have been cleaned up, a
	      message will be printed to notify	the user that bc is ready  for
	      more input.  All previously defined functions remain defined and
	      the value	of all non-auto	variables are the value	at  the	 point
	      of interruption.	All auto variables and function	parameters are
	      removed during the clean up process.  During  a  non-interactive
	      session, the SIGINT signal will terminate	the entire run of bc.

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

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

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

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

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

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

       multiply
	      The multiply routine may yield incorrect results if a number has
	      more than	LONG_MAX / 90 total digits.  For 32  bit  longs,  this
	      number is	23,860,929 digits.

       code size
	      Each  function and the "main" program are	limited	to 16384 bytes
	      of compiled byte code each.  This	 limit	(BC_MAX_SEGS)  can  be
	      easily changed to	have more than 16 segments of 1024 bytes.

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

ENVIRONMENT
       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	 argu-
	      ments  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 envi-
	      ronment 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 new-
	      line characters for long numbers.

FILES
       In  most	 installations,	 bc  is	completely self-contained.  Where exe-
       cutable size is of importance or	the C compiler does not	deal with very
       long  strings,  bc  will	 read  the standard math library from the file
       /usr/local/lib/libmath.b.  (The actual location may vary.   It  may  be
       /lib/libmath.b.)

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-gnu-utils@prep.ai.mit.edu.  Be sure to include
       the word	``bc'' somewhere in the	``Subject:'' field.

AUTHOR
       Philip A. Nelson
       phil@cs.wwu.edu

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

				       .				 bc(1)

NAME | SYNTAX | VERSION | DESCRIPTION | ENVIRONMENT | FILES | DIAGNOSTICS | BUGS | AUTHOR | ACKNOWLEDGEMENTS

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