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

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
BC(1)                   FreeBSD General Commands Manual                  BC(1)

NAME
     bc - arbitrary-precision arithmetic language and calculator

SYNOPSIS
     bc [-chlqv] [-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
     expressions 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
             expressions.  Synonym for -l.

     -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 1003.2 (``POSIX.2'') 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 operators.

     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), `\b' for backspace, `\f' for formfeed, `\n' for newline, `\r'
     for carriage return, `\t' 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.

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

SEE ALSO
     dc(1)

     "BC - An Arbitrary Precision Desk-Calculator Language",
     /usr/share/doc/usd/06.bc/.

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

     The flags [-ce] 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).

FreeBSD 11.0-PRERELEASE        January 22, 2010        FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | STANDARDS | HISTORY | AUTHORS | BUGS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=bc&sektion=1&manpath=FreeBSD+9.3-RELEASE>

home | help