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)

bc - arbitrary precision arithmetic language

The

input from any files given, then reads from the standard input. If the

standard input and standard output to

invocation of

described in the following sections.

resembles C and is a preprocessor for the desk calculator program

which it invokes automatically unless the

case the

The syntax for

Means a letter

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,

Means a statement.

Enclosed in

Simple variables:

Array elements:

The words

Arbitrarily long numbers with optional sign and decimal point. Strings of

fewer than

Square root

Number of significant decimal digits.

Number of digits right of decimal point.

(

(prefix and postfix; apply to names)

null statement

.string

sine

cosine

exponential

log

arctangent

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

retained on arithmetic operations in the manner of

The same letter may be used as an array, a function, and a simple

variable simultaneously. All variables are global to the program.

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:

Compiles only. The output is

standard output.

Defines the math functions and initializes

the default zero.

Defines the math functions and initializes

the default zero. All math results have the scale of

The following operands are supported:

A pathname of a text file containing

all cases of

In the shell, the following assigns an approximation of the first ten

digits of

Defines a function to compute an approximate value of the exponential

function:

Prints approximate values of the exponential function of the first ten

integers:

or

See environ(7) for descriptions of the following environment variables

that affect the execution of

The following exit values are returned:

All input files were processed successfully.

An error occurred.

mathematical library

to define BC_ parameters

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

+--------------------+-----------------+

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

+--------------------+-----------------+

|Interface Stability | Standard |

+--------------------+-----------------+

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

The

The

August 29, 2003 BC(1)