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bc - arbitrary precision arithmetic language

/usr/bin/bc [-c] [-l] [file]...

/usr/xpg6/bin/bc [-c] [-l] [file]...

The bc utility implements an arbitrary precision calculator. It takes input from any files given, then reads from the standard input. If the standard input and standard output to bc are attached to a terminal, the invocation of bc is interactive, causing behavioral constraints described in the following sections. bc processes a language that resembles C and is a preprocessor for the desk calculator program dc, which it invokes automatically unless the -c option is specified. In this case the dc input is sent to the standard output instead.

The syntax for bc programs is as follows: L

E S

Enclosed in /* and */.

Simple variables: L.

Array elements: L [ E ] (up to BC_DIM_MAX dimensions).

The words ibase, obase (limited to BC_BASE_MAX), and scale (limited to BC_SCALE_MAX).

Arbitrarily long numbers with optional sign and decimal point. Strings of fewer than BC_STRING_MAX characters, between double quotes ("). ( E ) sqrt ( E )

length ( E ) scale ( E ) L ( E , ... , E ) + - * / % ^ ++ -- == <= >= != < > = =+ =- =* =/ =% =^

E

{ S ;.\|.\|. ; S }

if ( E ) S

while ( E ) S

for ( E ; E ; E ) S

null statement

break

quit

.string

define L ( L ,.\|.\|.\|, L ) {

auto L ,.\|.\|.\|, L

S ;.\|.\|.\| S

return ( E )

}

s(x) c(x) e(x) l(x) a(x) j(n,x)

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. Either semicolons or new-lines may separate statements. Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc. 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 stacked during function calls. When using arrays as function arguments or defining them as automatic variables, empty square brackets must follow the array name.

The following operands are supported: -c

-l -l

The following operands are supported: file

Example 1 Setting the precision of a variable

In the shell, the following assigns an approximation of the first ten digits of n to the variable x:

x=$(printf "%s\en" 'scale = 10; 104348/33215' | bc)

Example 2 Defining a computing function

Defines a function to compute an approximate value of the exponential function:

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
 }
}

Example 3 Printing the approximate values of the function

Prints approximate values of the exponential function of the first ten integers:

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

or

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

See environ(5) for descriptions of the following environment variables that affect the execution of bc: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

The following exit values are returned: 0

unspecified /usr/lib/lib.b /usr/include/limits.h

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE

Interface Stability Standard

dc(1), awk(1), attributes(5), environ(5), standards(5)

The bc command does not recognize the logical operators && and |\||.

The for statement must have all three expressions (E's).