BC(1) User Commands BC(1)

NAME

bc - arbitrary precision arithmetic language

SYNOPSIS

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


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

DESCRIPTION

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.

USAGE

The syntax for bc programs is as follows:

L
Means a letter a-z,


E
Means an expression: a (mathematical or logical) value, an operand
that takes a value, or a combination of operands and operators that
evaluates to a value,


S
Means a statement.

Comments

Enclosed in /* and */.

Names (Operands)
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).

Other Operands

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

sqrt ( E )
Square root


length ( E )
Number of significant decimal digits.


scale ( E )
Number of digits right of decimal point.


L ( E , ... , E )

Operators

+ - * / % ^

(% is remainder; ^ is power)


++ --

(prefix and postfix; apply to names)


== <= >= != < >


= =+ =- =* =/ =% =^

Statements

E
{ S ;... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit


.string

Function Definitions

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

Functions in -l Math Library
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. 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.

OPTIONS

The following operands are supported:

-c
Compiles only. The output is dc commands that are sent to the
standard output.


/usr/bin/bc
-l
Defines the math functions and initializes scale to 20, instead of
the default zero.


/usr/xpg6/bin/bc
-l
Defines the math functions and initializes scale to 20, instead of
the default zero. All math results have the scale of 20.

OPERANDS

The following operands are supported:

file
A pathname of a text file containing bc program statements. After
all cases of file have been read, bc reads the standard input.

EXAMPLES

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\n" '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) }

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment variables
that affect the execution of bc: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and
NLSPATH.

EXIT STATUS

The following exit values are returned:

0
All input files were processed successfully.


unspecified
An error occurred.

FILES

/usr/lib/lib.b
mathematical library


/usr/include/limits.h
to define BC_ parameters

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO

awk(1), dc(1), attributes(7), environ(7), standards(7)

NOTES

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


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

August 29, 2003 BC(1)