Back to Contents
bc(1) General Commands Manual bc(1)
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 decimal digits used by bc to represent 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, dig‐
its 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 vari‐
able that has the value of the last printed number. These will be
discussed in further detail where appropriate. All of these vari‐
ables may have values assigned to them as well as used in expres‐
sions.
COMMENTS
Comments in bc start with the characters /* and end with the char‐
acters */. 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 nor‐
mally.
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. (Func‐
tions, 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 36. (Bases greater than 16 are
an extension.) Assigning a value outside this range to ibase will
result in a value of 2 or 36. Input numbers may contain the char‐
acters 0-9 and A-Z. (Note: They must be capitals. Lower case let‐
ters 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
ZZZ 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 expres‐
sions. 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 vari‐
able scale are 0 to the maximum number representable by a C inte‐
ger.
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 maxi‐
mum 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 expres‐
sions.
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. If a and b are the scales of the two expres‐
sions, then the scale of the result is:
min(a+b,max(scale,a,b))
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 com‐
pute 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 inte‐
ger 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 excep‐
tion 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 bool‐
ean 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 func‐
tions. 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 signifi‐
cant 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 new‐
lines 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 new‐
line. 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 new‐
line 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 LIM‐
ITS.) 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 arbi‐
trary 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 expres‐
sion 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 lit‐
erally, including any newline. No newline character is
printed after the string.
print list
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 charac‐
ter following the backslash will be ignored.
{ statement_list }
This is the compound statement. It allows multiple state‐
ments 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 state‐
ment. Expression1 is evaluated before the loop. Expres‐
sion2 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 exe‐
cuted. 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 parenthe‐
sis 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 termi‐
nated, 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 fol‐
lows:
define name ( parameters ) { newline
auto_list statement_list }
A function call is just an expression of the form "name(parame‐
ters)".
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 vari‐
ables because if function A calls function B, B may access func‐
tion A's auto variables by just using the same name, unless func‐
tion 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 sec‐
ond 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 con‐
stants 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 stan‐
dard function read, which will always use the current value of
ibase for conversion of numbers.
Several extensions have been added to functions. First, the for‐
mat of the definition has been slightly relaxed. The standard
requires the opening brace be on the same line as the define key‐
word and all other parts must be on following lines. This version
of bc will allow any number of newlines before and after the open‐
ing 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 funtion 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 func‐
tion 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 cal‐
culate 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 func‐
tion.
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 spe‐
cial variable, history is the number of lines of history retained.
For readline, a value of -1 means that an unlimited number of his‐
tory lines are retained. Setting the value of history to a posi‐
tive 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 pro‐
gram. There is an "undocumented" option (-c) that causes the pro‐
gram to output the byte code to the standard output instead of
running it. It was mainly used for debugging the parser and pre‐
paring the math library.
A major source of differences is extensions, where a feature is
extended to add more functionality and additions, where new fea‐
tures 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 envi‐
ronment variables starting with LC_.
names Traditional and POSIX bc have single letter names for func‐
tions, variables and arrays. They have been extended to be
multi-character names that start with a letter and may con‐
tain 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 implementa‐
tions 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 def‐
initions, 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 inval‐
idate 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 struc‐
tures have been cleaned up, a message will be printed to
notify the user that bc is ready for more input. All pre‐
viously defined functions remain defined and the value of
all non-auto variables are the value at the point of inter‐
ruption. All auto variables and function parameters are
removed during the clean up process. During a non-interac‐
tive session, the SIGINT signal will terminate the entire
run of bc.
LIMITS
The following are the limits currently in place for this bc pro‐
cessor. 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 maxi‐
mum input base is 16.
BC_DIM_MAX
This is currently an arbitrary limit of 65535 as distrib‐
uted. 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 dec‐
imal 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 for‐
mat is the same as the command line arguments. These argu‐
ments are processed first, so any files listed in the envi‐
ronment 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 charac‐
ters in an output line for numbers. This includes the back‐
slash and newline characters for long numbers. As an
extension, the value of zero disables the multi-line fea‐
ture. 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 com‐
pile and run time diagnostics that should be self-explanatory.
BUGS
Error recovery is not very good yet.
Email bug reports to bug-bc@gnu.org. Be sure to include the word
``bc'' somewhere in the ``Subject:'' field.
AUTHOR
Philip A. Nelson
philnelson@acm.org
ACKNOWLEDGEMENTS
The author would like to thank Steve Sommars (Steve.Som‐
mars@att.com) for his extensive help in testing the implementa‐
tion. Many great suggestions were given. This is a much better
product due to his involvement.
GNU Project 2006-06-11 bc(1)