BC(1)							    BSD General Commands Manual 						     BC(1)

NAME

     bc -- arbitrary-precision arithmetic language and calculator

SYNOPSIS

     bc [-chlv] [-e expression] [file ...]

DESCRIPTION

     bc is an interactive processor for a language which resembles C but provides unlimited precision arithmetic.  It takes input from any expres-
     sions on the command line and any files given, then reads the standard input.

     Options available:

     -c      bc is actually a preprocessor for dc(1), which it invokes automatically, unless the -c (compile only) option is present.  In this
	     case the generated dc(1) instructions are sent to the standard output, instead of being interpreted by a running dc(1) process.

     -e expression, --expression expression
	     Evaluate expression.  If multiple -e options are specified, they are processed in the order given, separated by newlines.

     -h, --help
	     Prints usage information.

     -l, --mathlib
	     Allow specification of an arbitrary precision math library.  The definitions in the library are available to command line expres-
	     sions.

     -v, --version
	     Prints version information.

     The syntax for bc programs is as follows: 'L' means letter a-z; 'E' means expression; 'S' means statement.  As a non-portable extension, it
     is possible to use long names in addition to single letter names.	A long name is a sequence starting with a lowercase letter followed by any
     number of lowercase letters and digits.  The underscore character ('_') counts as a letter.

     Comments
	   are enclosed in /* and */
	   are enclosed in # and the next newline

     The newline is not part of the line comment, which in itself is a non-portable extension.

     Names
	   simple variables: L
	   array elements: L [ E ]
	   The words `ibase', `obase', and `scale'
	   The word `last' or a single dot

     Other operands
	   arbitrarily long numbers with optional sign and decimal point
	   ( E )
	   sqrt ( E )
	   length ( E )   number of significant decimal digits
	   scale ( E )	  number of digits right of decimal point
	   L ( E , ... , E )

     The sequence '<newline><whitespace>' is ignored within numbers.

     Operators

     The following arithmetic and logical operators can be used.  The semantics of the operators is the same as in the C language.  They are
     listed in order of decreasing precedence.	Operators in the same group have the same precedence.

	   Operator		  Associativity    Description
	   ++ --		  none		   increment, decrement
	   -			  none		   unary minus
	   ^			  right 	   power
	   * / %		  left		   multiply, divide, modulus
	   + -			  left		   plus, minus
	   = += -= *= /= %= ^=	  right 	   assignment
	   == <= >= != < >	  none		   relational
	   !			  none		   boolean not
	   &&			  left		   boolean and
	   ||			  left		   boolean or

     Note the following:

	   o   The relational operators may appear in any expression.  The IEEE Std 1003.1-2008 (``POSIX.1'') standard only allows them in the
	       conditional expression of an 'if', 'while' or 'for' statement.

	   o   The relational operators have a lower precedence than the assignment operators.	This has the consequence that the expression a = b
	       < c is interpreted as (a = b) < c, which is probably not what the programmer intended.

	   o   In contrast with the C language, the relational operators all have the same precedence, and are non-associative.  The expression a
	       < b < c will produce a syntax error.

	   o   The boolean operators (!, && and ||) are non-portable extensions.

	   o   The boolean not (!) operator has much lower precedence than the same operator in the C language.  This has the consequence that the
	       expression !a < b is interpreted as !(a < b).  Prudent programmers use parentheses when writing expressions involving boolean oper-
	       ators.

     Statements
	   E
	   { S ; ... ; S }
	   if ( E ) S
	   if ( E ) S else S
	   while ( E ) S
	   for ( E ; E ; E ) S
	   null statement
	   break
	   continue
	   quit
	   a string of characters, enclosed in double quotes
	   print E ,..., E

     A string may contain any character, except double quote.  The if statement with an else branch is a non-portable extension.  All three E's in
     a for statement may be empty.  This is a non-portable extension.  The continue and print statements are also non-portable extensions.

     The print statement takes a list of comma-separated expressions.  Each expression in the list is evaluated and the computed value is printed
     and assigned to the variable `last'.  No trailing newline is printed.  The expression may also be a string enclosed in double quotes.  Within
     these strings the following escape sequences may be used: 'a' for bell (alert), '' for backspace, 'f' for formfeed, '
' for newline,
     '
' for carriage return, '	' for tab, 'q' for double quote and '\' for backslash.  Any other character following a backslash will be
     ignored.  Strings will not be assigned to `last'.

     Function definitions

	   define L ( L ,..., L ) {
		auto L, ... , L
		S; ... S
		return ( E )
	   }

     As a non-portable extension, the opening brace of the define statement may appear on the next line.  The return statement may also appear in
     the following forms:

	   return
	   return ()
	   return E

     The first two are equivalent to the statement ``return 0''.  The last form is a non-portable extension.  Not specifying a return statement is
     equivalent to writing ``return (0)''.

     Functions available in the math library, which is loaded by specifying the -l flag on the command line

	   s(x)    sine
	   c(x)    cosine
	   e(x)    exponential
	   l(x)    log
	   a(x)    arctangent
	   j(n,x)  Bessel function

     All function arguments are passed by value.

     The value of a statement that is an expression is printed unless the main operator is an assignment.  The value printed is assigned to the
     special variable `last'.  This is a non-portable extension.  A single dot may be used as a synonym for `last'.  Either semicolons or newlines
     may separate statements.  Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc(1).
     Assignments to ibase or obase set the input and output number radix respectively.

     The same letter may be used as an array, a function, and a simple variable simultaneously.  All variables are global to the program.  `Auto'
     variables are pushed down during function calls.  When using arrays as function arguments or defining them as automatic variables, empty
     square brackets must follow the array name.

     For example

	   scale = 20
	   define e(x){
		   auto a, b, c, i, s
		   a = 1
		   b = 1
		   s = 1
		   for(i=1; 1==1; i++){
			   a = a*x
			   b = b*i
			   c = a/b
			   if(c == 0) return(s)
			   s = s+c
		   }
	   }

     defines a function to compute an approximate value of the exponential function and

	   for(i=1; i<=10; i++) e(i)

     prints approximate values of the exponential function of the first ten integers.

	   $ bc -l -e 'scale = 500; 2 * a(2^10000)' -e quit

     prints an approximation of pi.

COMMAND LINE EDITING

     bc supports interactive command line editing, via the editline(3) library.  It is enabled by default if input is from a tty.  Previous lines
     can be recalled and edited with the arrow keys, and other GNU Emacs-style editing keys may be used as well.

     The editline(3) library is configured with a .editrc file - refer to editrc(5) for more information.

FILES

     /usr/share/misc/bc.library  math library, read when the -l option is specified on the command line.

COMPATIBILITY

     The -q and --quiet options are no-ops for compatibility with some other implementations of bc and their use is discouraged.

SEE ALSO

     dc(1)

STANDARDS

     The bc utility is compliant with the IEEE Std 1003.1-2008 (``POSIX.1'') specification.

     The flags [-ce], as well as the parts noted above, are extensions to that specification.

HISTORY

     The bc command first appeared in Version 6 AT&T UNIX.  A complete rewrite of the bc command first appeared in OpenBSD 3.5.

AUTHORS

     The original version of the bc command was written by Robert Morris and Lorinda Cherry.  The current version of the bc utility was written by
     Otto Moerbeek.

BUGS

     'Quit' is interpreted when read, not when executed.

     Some non-portable extensions, as found in the GNU version of the bc utility are not implemented (yet).

BSD
								  April 16, 2014							       BSD