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**PROGRAM:**

**NAME**

bc - An arbitrary precision calculator language

**SYNTAX**

**bc**[

**-hlwsqv**] [long-options] [

__file__

__...__]

**DESCRIPTION**

**bc**is a language that supports arbitrary precision numbers with interactive execution of

statements. There are some similarities in the syntax to the C programming language. A

standard math library is available by command line option. If requested, the math library

is defined before processing any files.

**bc**starts by processing code from all the files

listed on the command line in the order listed. After all files have been processed,

**bc**

reads from the standard input. All code is executed as it is read. (If a file contains a

command to halt the processor,

**bc**will never read from the standard input.)

This version of

**bc**contains several extensions beyond traditional

**bc**implementations and

the POSIX draft standard. Command line options can cause these extensions to print a

warning or to be rejected. This document describes the language accepted by this

processor. Extensions will be identified as such.

**OPTIONS**

-h, --help

Print the usage and exit.

-i, --interactive

Force interactive mode.

-l, --mathlib

Define the standard math library.

-w, --warn

Give warnings for extensions to POSIX

**bc**.

-s, --standard

Process exactly the POSIX

**bc**language.

-q, --quiet

Do not print the normal GNU bc welcome.

-v, --version

Print the version number and copyright and quit.

**NUMBERS**

The most basic element in

**bc**is the number. Numbers are arbitrary precision numbers.

This precision is both in the integer part and the fractional part. All numbers are

represented internally in decimal and all computation is done in decimal. (This version

truncates results from divide and multiply operations.) There are two attributes of

numbers, the length and the scale. The length is the total number of significant decimal

digits in a number and the scale is the total number of decimal digits after the decimal

point. For example:

.000001 has a length of 6 and scale of 6.

1935.000 has a length of 7 and a scale of 3.

**VARIABLES**

Numbers are stored in two types of variables, simple variables and arrays. Both simple

variables and array variables are named. Names begin with a letter followed by any number

of letters, digits and underscores. All letters must be lower case. (Full alpha-numeric

names are an extension. In POSIX

**bc**all names are a single lower case letter.) The type

of variable is clear by the context because all array variable names will be followed by

brackets ([]).

There are four special variables,

**scale,**

**ibase,**

**obase,**and

**last**.

**scale**defines how some

operations use digits after the decimal point. The default value of

**scale**is 0.

**ibase**

and

**obase**define the conversion base for input and output numbers. The default for both

input and output is base 10.

**last**(an extension) is a variable that has the value of the

last printed number. These will be discussed in further detail where appropriate. All of

these variables may have values assigned to them as well as used in expressions.

**COMMENTS**

Comments in

**bc**start with the characters

**/***and end with the characters

***/**. Comments may

start anywhere and appear as a single space in the input. (This causes comments to

delimit other input items. For example, a comment can not be found in the middle of a

variable name.) Comments include any newlines (end of line) between the start and the end

of the comment.

To support the use of scripts for

**bc**, a single line comment has been added as an

extension. A single line comment starts at a

**#**character and continues to the next end of

the line. The end of line character is not part of the comment and is processed normally.

**EXPRESSIONS**

The numbers are manipulated by expressions and statements. Since the language was

designed to be interactive, statements and expressions are executed as soon as possible.

There is no "main" program. Instead, code is executed as it is encountered. (Functions,

discussed in detail later, are defined when encountered.)

A simple expression is just a constant.

**bc**converts constants into internal decimal

numbers using the current input base, specified by the variable

**ibase**. (There is an

exception in functions.) The legal values of

**ibase**are 2 through 16. Assigning a value

outside this range to

**ibase**will result in a value of 2 or 16. Input numbers may contain

the characters 0–9 and A–F. (Note: They must be capitals. Lower case letters are variable

names.) Single digit numbers always have the value of the digit regardless of the value

of

**ibase**. (i.e. A = 10.) For multi-digit numbers,

**bc**changes all input digits greater or

equal to ibase to the value of

**ibase**-1. This makes the number

**FFF**always be the largest 3

digit number of the input base.

Full expressions are similar to many other high level languages. Since there is only one

kind of number, there are no rules for mixing types. Instead, there are rules on the

scale of expressions. Every expression has a scale. This is derived from the scale of

original numbers, the operation performed and in many cases, the value of the variable

**scale**. Legal values of the variable

**scale**are 0 to the maximum number representable by a C

integer.

In the following descriptions of legal expressions, "expr" refers to a complete expression

and "var" refers to a simple or an array variable. A simple variable is just a

__name__

and an array variable is specified as

__name__[

__expr__]

Unless specifically mentioned the scale of the result is the maximum scale of the

expressions involved.

- expr The result is the negation of the expression.

++ var The variable is incremented by one and the new value is the result of the

expression.

-- var The variable is decremented by one and the new value is the result of the

expression.

var ++

The result of the expression is the value of the variable and then the variable is

incremented by one.

var -- The result of the expression is the value of the variable and then the variable is

decremented by one.

expr + expr

The result of the expression is the sum of the two expressions.

expr - expr

The result of the expression is the difference of the two expressions.

expr * expr

The result of the expression is the product of the two expressions.

expr / expr

The result of the expression is the quotient of the two expressions. The scale of

the result is the value of the variable

**scale**.

expr % expr

The result of the expression is the "remainder" and it is computed in the following

way. To compute a%b, first a/b is computed to

**scale**digits. That result is used

to compute a-(a/b)*b to the scale of the maximum of

**scale**+scale(b) and scale(a).

If

**scale**is set to zero and both expressions are integers this expression is the

integer remainder function.

expr ^ expr

The result of the expression is the value of the first raised to the second. The

second expression must be an integer. (If the second expression is not an integer,

a warning is generated and the expression is truncated to get an integer value.)

The scale of the result is

**scale**if the exponent is negative. If the exponent is

positive the scale of the result is the minimum of the scale of the first

expression times the value of the exponent and the maximum of

**scale**and the scale

of the first expression. (e.g. scale(a^b) = min(scale(a)*b, max(

**scale,**

scale(a))).) It should be noted that expr^0 will always return the value of 1.

( expr )

This alters the standard precedence to force the evaluation of the expression.

var = expr

The variable is assigned the value of the expression.

var <op>= expr

This is equivalent to "var = var <op> expr" with the exception that the "var" part

is evaluated only once. This can make a difference if "var" is an array.

Relational expressions are a special kind of expression that always evaluate to 0 or 1, 0

if the relation is false and 1 if the relation is true. These may appear in any legal

expression. (POSIX bc requires that relational expressions are used only in if, while,

and for statements and that only one relational test may be done in them.) The relational

operators are

expr1 < expr2

The result is 1 if expr1 is strictly less than expr2.

expr1 <= expr2

The result is 1 if expr1 is less than or equal to expr2.

expr1 > expr2

The result is 1 if expr1 is strictly greater than expr2.

expr1 >= expr2

The result is 1 if expr1 is greater than or equal to expr2.

expr1 == expr2

The result is 1 if expr1 is equal to expr2.

expr1 != expr2

The result is 1 if expr1 is not equal to expr2.

Boolean operations are also legal. (POSIX

**bc**does NOT have boolean operations). The

result of all boolean operations are 0 and 1 (for false and true) as in relational

expressions. The boolean operators are:

!expr The result is 1 if expr is 0.

expr && expr

The result is 1 if both expressions are non-zero.

expr || expr

The result is 1 if either expression is non-zero.

The expression precedence is as follows: (lowest to highest)

|| operator, left associative

&& operator, left associative

! operator, nonassociative

Relational operators, left associative

Assignment operator, right associative

+ and - operators, left associative

*, / and % operators, left associative

^ operator, right associative

unary - operator, nonassociative

++ and -- operators, nonassociative

This precedence was chosen so that POSIX compliant

**bc**programs will run correctly. This

will cause the use of the relational and logical operators to have some unusual behavior

when used with assignment expressions. Consider the expression:

a = 3 < 5

Most C programmers would assume this would assign the result of "3 < 5" (the value 1) to

the variable "a". What this does in

**bc**is assign the value 3 to the variable "a" and then

compare 3 to 5. It is best to use parenthesis when using relational and logical operators

with the assignment operators.

There are a few more special expressions that are provided in

**bc**. These have to do with

user defined functions and standard functions. They all appear as "

__name__

**(**

__parameters__

**)**".

See the section on functions for user defined functions. The standard functions are:

length ( expression )

The value of the length function is the number of significant digits in the

expression.

read ( )

The read function (an extension) will read a number from the standard input,

regardless of where the function occurs. Beware, this can cause problems with the

mixing of data and program in the standard input. The best use for this function

is in a previously written program that needs input from the user, but never allows

program code to be input from the user. The value of the read function is the

number read from the standard input using the current value of the variable

**ibase**

for the conversion base.

scale ( expression )

The value of the scale function is the number of digits after the decimal point in

the expression.

sqrt ( expression )

The value of the sqrt function is the square root of the expression. If the

expression is negative, a run time error is generated.

**STATEMENTS**

Statements (as in most algebraic languages) provide the sequencing of expression

evaluation. In

**bc**statements are executed "as soon as possible." Execution happens when

a newline in encountered and there is one or more complete statements. Due to this

immediate execution, newlines are very important in

**bc**. In fact, both a semicolon and a

newline are used as statement separators. An improperly placed newline will cause a

syntax error. Because newlines are statement separators, it is possible to hide a newline

by using the backslash character. The sequence "\<nl>", where <nl> is the newline appears

to

**bc**as whitespace instead of a newline. A statement list is a series of statements

separated by semicolons and newlines. The following is a list of

**bc**statements and what

they do: (Things enclosed in brackets ([]) are optional parts of the statement.)

expression

This statement does one of two things. If the expression starts with "<variable>

<assignment> ...", it is considered to be an assignment statement. If the

expression is not an assignment statement, the expression is evaluated and printed

to the output. After the number is printed, a newline is printed. For example,

"a=1" is an assignment statement and "(a=1)" is an expression that has an embedded

assignment. All numbers that are printed are printed in the base specified by the

variable

**obase**. The legal values for

**obase**are 2 through BC_BASE_MAX. (See the

section LIMITS.) For bases 2 through 16, the usual method of writing numbers is

used. For bases greater than 16,

**bc**uses a multi-character digit method of

printing the numbers where each higher base digit is printed as a base 10 number.

The multi-character digits are separated by spaces. Each digit contains the number

of characters required to represent the base ten value of "obase-1". Since numbers

are of arbitrary precision, some numbers may not be printable on a single output

line. These long numbers will be split across lines using the "\" as the last

character on a line. The maximum number of characters printed per line is 70. Due

to the interactive nature of

**bc**, printing a number causes the side effect of

assigning the printed value to the special variable

**last**. This allows the user to

recover the last value printed without having to retype the expression that printed

the number. Assigning to

**last**is legal and will overwrite the last printed value

with the assigned value. The newly assigned value will remain until the next

number is printed or another value is assigned to

**last**. (Some installations may

allow the use of a single period (.) which is not part of a number as a short hand

notation for for

**last**.)

string The string is printed to the output. Strings start with a double quote character

and contain all characters until the next double quote character. All characters

are take literally, including any newline. No newline character is printed after

the string.

The print statement (an extension) provides another method of output. The "list"

is a list of strings and expressions separated by commas. Each string or

expression is printed in the order of the list. No terminating newline is printed.

Expressions are evaluated and their value is printed and assigned to the variable

**last**. Strings in the print statement are printed to the output and may contain

special characters. Special characters start with the backslash character (\).

The special characters recognized by

**bc**are "a" (alert or bell), "b" (backspace),

"f" (form feed), "n" (newline), "r" (carriage return), "q" (double quote), "t"

(tab), and "\" (backslash). Any other character following the backslash will be

ignored.

{ statement_list }

This is the compound statement. It allows multiple statements to be grouped

together for execution.

**if**( expression ) statement1 [

**else**statement2]

The if statement evaluates the expression and executes statement1 or statement2

depending on the value of the expression. If the expression is non-zero,

statement1 is executed. If statement2 is present and the value of the expression

is 0, then statement2 is executed. (The else clause is an extension.)

**while**( expression ) statement

The while statement will execute the statement while the expression is non-zero.

It evaluates the expression before each execution of the statement. Termination

of the loop is caused by a zero expression value or the execution of a break

statement.

**for**( [expression1] ; [expression2] ; [expression3] ) statement

The for statement controls repeated execution of the statement. Expression1 is

evaluated before the loop. Expression2 is evaluated before each execution of the

statement. If it is non-zero, the statement is evaluated. If it is zero, the loop

is terminated. After each execution of the statement, expression3 is evaluated

before the reevaluation of expression2. If expression1 or expression3 are missing,

nothing is evaluated at the point they would be evaluated. If expression2 is

missing, it is the same as substituting the value 1 for expression2. (The optional

expressions are an extension. POSIX

**bc**requires all three expressions.) The

following is equivalent code for the for statement:

expression1;

while (expression2) {

statement;

expression3;

}

**break**This statement causes a forced exit of the most recent enclosing while statement or

for statement.

**continue**

The continue statement (an extension) causes the most recent enclosing for

statement to start the next iteration.

**halt**The halt statement (an extension) is an executed statement that causes the

**bc**

processor to quit only when it is executed. For example, "if (0 == 1) halt" will

not cause

**bc**to terminate because the halt is not executed.

**return**Return the value 0 from a function. (See the section on functions.)

**return**( expression )

Return the value of the expression from a function. (See the section on

functions.) As an extension, the parenthesis are not required.

**PSEUDO**

**STATEMENTS**

These statements are not statements in the traditional sense. They are not executed

statements. Their function is performed at "compile" time.

**limits**Print the local limits enforced by the local version of

**bc**. This is an extension.

**quit**When the quit statement is read, the

**bc**processor is terminated, regardless of

where the quit statement is found. For example, "if (0 == 1) quit" will cause

**bc**

to terminate.

**warranty**

Print a longer warranty notice. This is an extension.

**FUNCTIONS**

Functions provide a method of defining a computation that can be executed later.

Functions in

**bc**always compute a value and return it to the caller. Function definitions

are "dynamic" in the sense that a function is undefined until a definition is encountered

in the input. That definition is then used until another definition function for the same

name is encountered. The new definition then replaces the older definition. A function

is defined as follows:

**define**

__name__

**(**

__parameters__

**)**

**{**

__newline__

__auto_list__

__statement_list__

**}**

A function call is just an expression of the form "

__name__

**(**

__parameters__

**)**".

Parameters are numbers or arrays (an extension). In the function definition, zero or more

parameters are defined by listing their names separated by commas. All parameters are

call by value parameters. Arrays are specified in the parameter definition by the

notation "

__name__

**[]**". In the function call, actual parameters are full expressions for

number parameters. The same notation is used for passing arrays as for defining array

parameters. The named array is passed by value to the function. Since function

definitions are dynamic, parameter numbers and types are checked when a function is

called. Any mismatch in number or types of parameters will cause a runtime error. A

runtime error will also occur for the call to an undefined function.

The

__auto_list__is an optional list of variables that are for "local" use. The syntax of

the auto list (if present) is "

**auto**

__name__, ... ;". (The semicolon is optional.) Each

__name__

is the name of an auto variable. Arrays may be specified by using the same notation as

used in parameters. These variables have their values pushed onto a stack at the start of

the function. The variables are then initialized to zero and used throughout the

execution of the function. At function exit, these variables are popped so that the

original value (at the time of the function call) of these variables are restored. The

parameters are really auto variables that are initialized to a value provided in the

function call. Auto variables are different than traditional local variables because if

function A calls function B, B may access function A's auto variables by just using the

same name, unless function B has called them auto variables. Due to the fact that auto

variables and parameters are pushed onto a stack,

**bc**supports recursive functions.

The function body is a list of

**bc**statements. Again, statements are separated by

semicolons or newlines. Return statements cause the termination of a function and the

return of a value. There are two versions of the return statement. The first form,

"

**return**", returns the value 0 to the calling expression. The second form, "

**return**

**(**

__expression__

**)**", computes the value of the expression and returns that value to the calling

expression. There is an implied "

**return**

**(0)**" at the end of every function. This allows a

function to terminate and return 0 without an explicit return statement.

Functions also change the usage of the variable

**ibase**. All constants in the function body

will be converted using the value of

**ibase**at the time of the function call. Changes of

**ibase**will be ignored during the execution of the function except for the standard

function

**read**, which will always use the current value of

**ibase**for conversion of numbers.

Several extensions have been added to functions. First, the format of the definition has

been slightly relaxed. The standard requires the opening brace be on the same line as the

**define**keyword and all other parts must be on following lines. This version of

**bc**will

allow any number of newlines before and after the opening brace of the function. For

example, the following definitions are legal.

define d (n) { return (2*n); }

define d (n)

{ return (2*n); }

Functions may be defined as

**void**. A void function returns no value and thus may not be

used in any place that needs a value. A void function does not produce any output when

called by itself on an input line. The key word

**void**is placed between the key word

**define**and the function name. For example, consider the following session.

define py (y) { print "--->", y, "<---", "\n"; }

define void px (x) { print "--->", x, "<---", "\n"; }

py(1)

--->1<---

0

px(1)

--->1<---

Since

**py**is not a void function, the call of

**py(1)**prints the desired output and then

prints a second line that is the value of the function. Since the value of a function

that is not given an explicit return statement is zero, the zero is printed. For

**px(1)**,

no zero is printed because the function is a void function.

Also, call by variable for arrays was added. To declare a call by variable array, the

declaration of the array parameter in the function definition looks like "

__*name__

**[]**". The

call to the function remains the same as call by value arrays.

**MATH**

**LIBRARY**

If

**bc**is invoked with the

**-l**option, a math library is preloaded and the default scale is

set to 20. The math functions will calculate their results to the scale set at the time

of their call. The math library defines the following functions:

s (

__x__) The sine of x, x is in radians.

c (

__x__) The cosine of x, x is in radians.

a (

__x__) The arctangent of x, arctangent returns radians.

l (

__x__) The natural logarithm of x.

e (

__x__) The exponential function of raising e to the value x.

j (

__n,x__)

The Bessel function of integer order n of x.

**EXAMPLES**

In /bin/sh, the following will assign the value of "pi" to the shell variable

**pi**.

pi=$(echo "scale=10; 4*a(1)" | bc -l)

The following is the definition of the exponential function used in the math library.

This function is written in POSIX

**bc**.

scale = 20

/* Uses the fact that e^x = (e^(x/2))^2

When x is small enough, we use the series:

e^x = 1 + x + x^2/2! + x^3/3! + ...

*/

define e(x) {

auto a, d, e, f, i, m, v, z

/* Check the sign of x. */

if (x<0) {

m = 1

x = -x

}

/* Precondition x. */

z = scale;

scale = 4 + z + .44*x;

while (x > 1) {

f += 1;

x /= 2;

}

/* Initialize the variables. */

v = 1+x

a = x

d = 1

for (i=2; 1; i++) {

e = (a *= x) / (d *= i)

if (e == 0) {

if (f>0) while (f--) v = v*v;

scale = z

if (m) return (1/v);

return (v/1);

}

v += e

}

}

The following is code that uses the extended features of

**bc**to implement a simple program

for calculating checkbook balances. This program is best kept in a file so that it can be

used many times without having to retype it at every use.

scale=2

print "\nCheck book program!\n"

print " Remember, deposits are negative transactions.\n"

print " Exit by a 0 transaction.\n\n"

print "Initial balance? "; bal = read()

bal /= 1

print "\n"

while (1) {

"current balance = "; bal

"transaction? "; trans = read()

if (trans == 0) break;

bal -= trans

bal /= 1

}

quit

The following is the definition of the recursive factorial function.

define f (x) {

if (x <= 1) return (1);

return (f(x-1) * x);

}

**READLINE**

**AND**

**LIBEDIT**

**OPTIONS**

GNU

**bc**can be compiled (via a configure option) to use the GNU

**readline**input editor

library or the BSD

**libedit**library. This allows the user to do editing of lines before

sending them to

**bc**. It also allows for a history of previous lines typed. When this

option is selected,

**bc**has one more special variable. This special variable,

**history**is

the number of lines of history retained. For

**readline**, a value of -1 means that an

unlimited number of history lines are retained. Setting the value of

**history**to a

positive number restricts the number of history lines to the number given. The value of 0

disables the history feature. The default value is 100. For more information, read the

user manuals for the GNU

**readline**,

**history**and BSD

**libedit**libraries. One can not enable

both

**readline**and

**libedit**at the same time.

**DIFFERENCES**

This version of

**bc**was implemented from the POSIX P1003.2/D11 draft and contains several

differences and extensions relative to the draft and traditional implementations. It is

not implemented in the traditional way using

__dc(1).__This version is a single process

which parses and runs a byte code translation of the program. There is an "undocumented"

option (-c) that causes the program to output the byte code to the standard output instead

of running it. It was mainly used for debugging the parser and preparing the math

library.

A major source of differences is extensions, where a feature is extended to add more

functionality and additions, where new features are added. The following is the list of

differences and extensions.

LANG environment

This version does not conform to the POSIX standard in the processing of the LANG

environment variable and all environment variables starting with LC_.

names Traditional and POSIX

**bc**have single letter names for functions, variables and

arrays. They have been extended to be multi-character names that start with a

letter and may contain letters, numbers and the underscore character.

Strings

Strings are not allowed to contain NUL characters. POSIX says all characters must

be included in strings.

last POSIX

**bc**does not have a

**last**variable. Some implementations of

**bc**use the period

(.) in a similar way.

comparisons

POSIX

**bc**allows comparisons only in the if statement, the while statement, and the

second expression of the for statement. Also, only one relational operation is

allowed in each of those statements.

if statement, else clause

POSIX

**bc**does not have an else clause.

for statement

POSIX

**bc**requires all expressions to be present in the for statement.

&&, ||, !

POSIX

**bc**does not have the logical operators.

read function

POSIX

**bc**does not have a read function.

print statement

POSIX

**bc**does not have a print statement.

continue statement

POSIX

**bc**does not have a continue statement.

return statement

POSIX

**bc**requires parentheses around the return expression.

array parameters

POSIX

**bc**does not (currently) support array parameters in full. The POSIX grammar

allows for arrays in function definitions, but does not provide a method to specify

an array as an actual parameter. (This is most likely an oversight in the

grammar.) Traditional implementations of

**bc**have only call by value array

parameters.

function format

POSIX

**bc**requires the opening brace on the same line as the

**define**key word and the

**auto**statement on the next line.

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

POSIX

**bc**does not require these "old style" assignment operators to be defined.

This version may allow these "old style" assignments. Use the limits statement to

see if the installed version supports them. If it does support the "old style"

assignment operators, the statement "a =- 1" will decrement

**a**by 1 instead of

setting

**a**to the value -1.

spaces in numbers

Other implementations of

**bc**allow spaces in numbers. For example, "x=1 3" would

assign the value 13 to the variable x. The same statement would cause a syntax

error in this version of

**bc**.

errors and execution

This implementation varies from other implementations in terms of what code will be

executed when syntax and other errors are found in the program. If a syntax error

is found in a function definition, error recovery tries to find the beginning of a

statement and continue to parse the function. Once a syntax error is found in the

function, the function will not be callable and becomes undefined. Syntax errors

in the interactive execution code will invalidate the current execution block. The

execution block is terminated by an end of line that appears after a complete

sequence of statements. For example,

a = 1

b = 2

has two execution blocks and

{ a = 1

b = 2 }

has one execution block. Any runtime error will terminate the execution of the current

execution block. A runtime warning will not terminate the current execution block.

Interrupts

During an interactive session, the SIGINT signal (usually generated by the control-

C character from the terminal) will cause execution of the current execution block

to be interrupted. It will display a "runtime" error indicating which function was

interrupted. After all runtime structures have been cleaned up, a message will be

printed to notify the user that

**bc**is ready for more input. All previously defined

functions remain defined and the value of all non-auto variables are the value at

the point of interruption. All auto variables and function parameters are removed

during the clean up process. During a non-interactive session, the SIGINT signal

will terminate the entire run of

**bc**.

**LIMITS**

The following are the limits currently in place for this

**bc**processor. Some of them may

have been changed by an installation. Use the limits statement to see the actual values.

BC_BASE_MAX

The maximum output base is currently set at 999. The maximum input base is 16.

BC_DIM_MAX

This is currently an arbitrary limit of 65535 as distributed. Your installation

may be different.

BC_SCALE_MAX

The number of digits after the decimal point is limited to INT_MAX digits. Also,

the number of digits before the decimal point is limited to INT_MAX digits.

BC_STRING_MAX

The limit on the number of characters in a string is INT_MAX characters.

exponent

The value of the exponent in the raise operation (^) is limited to LONG_MAX.

variable names

The current limit on the number of unique names is 32767 for each of simple

variables, arrays and functions.

**ENVIRONMENT** **VARIABLES**

The following environment variables are processed by

**bc**:

POSIXLY_CORRECT

This is the same as the

**-s**option.

BC_ENV_ARGS

This is another mechanism to get arguments to

**bc**. The format is the same as the

command line arguments. These arguments are processed first, so any files listed

in the environment arguments are processed before any command line argument files.

This allows the user to set up "standard" options and files to be processed at

every invocation of

**bc**. The files in the environment variables would typically

contain function definitions for functions the user wants defined every time

**bc**is

run.

BC_LINE_LENGTH

This should be an integer specifying the number of characters in an output line for

numbers. This includes the backslash and newline characters for long numbers. As

an extension, the value of zero disables the multi-line feature. Any other value

of this variable that is less than 3 sets the line length to 70.

**DIAGNOSTICS**

If any file on the command line can not be opened,

**bc**will report that the file is

unavailable and terminate. Also, there are compile and run time diagnostics that should

be self-explanatory.

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