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bc(1)
NAME
bc - Provides a processor for arbitrary-precision arithmetic language
SYNOPSIS
bc [-cl] [file...]
The bc command is an interactive program that provides unlimited precision
arithmetic. It is a preprocessor for the dc command.
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
bc: XCU5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
OPTIONS
-c [Tru64 UNIX] Compiles file, but does not invoke dc.
-l Includes a library of mathematical functions. Also sets the number of
digits retained after the decimal point (the scale) to 20; by default
the scale is 0.
OPERANDS
file
Pathname of a text file containing program statements. After file has
been exhausted, standard input is read.
DESCRIPTION
[Tru64 UNIX] The bc command invokes dc automatically, unless the -c
(compile only) option is specified. If the -c option is specified, the
output from bc goes to the standard output.
The bc command lets you specify an input and output base in decimal, octal,
or hexadecimal (the default is decimal). The command also has a scaling
provision for decimal point notation. The syntax for bc is similar to that
of the C language.
The bc command takes input first from the specified file. When bc reaches
the end of the input file, it reads standard input.
In the following description of syntax for bc, letter means one of the
letters a-z.
Comments
Comments are enclosed in /* and */.
Names
Simple variables: letter
Array elements: letter[expression]
The words ibase, obase, and scale
Other Operands
Arbitrarily long numbers with optional sign and decimal point.
(expression)
sqrt (expression)
length (expression)
Number of significant decimal digits
scale (expression)
Number of digits to right of decimal point
letter (expression,...,expression)
Operators
+ - * / % ^ (% is remainder; ^ is power)
++ -- (prefix and suffix; apply to names)
== <= >= != <>
= =+ =- =* =/ =% ^=
+= -= *= /= %=
Statements
expression
{statement;...;statement}
if (expression) statement
while (expression) statement
for (expression;expression;expression) statement
(null statement)
break
quit
Function Definitions
define letter ( letter,...,letter ) {
auto letter,...,letter
statement;...statement
return ( expression )
}
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
General Syntax
All function parameters are passed by value.
The value of a statement that is an expression is displayed, unless the
main operator is an assignment. A semicolon or newline character separates
statements. Assignments to scale control the number of decimal places
printed on output and maintained during multiplication, division, and
exponentiation. Assignments to ibase or obase set the input and output
number radix, respectively.
The same letter may refer to an array, a function, and a simple variable
simultaneously. All variables are global to the program. Automatic
variables are pushed down during function calls. When you use arrays as
function parameters, or define them as automatic variables, empty brackets
must follow the array name.
All for statements must have all three expressions.
The quit statement is interpreted when read, not when executed.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
!0 An error occurred.
EXAMPLES
When you enter bc expressions directly from the keyboard, press the End-
of-File key sequence to end the bc session and return to the shell command
line.
1. To use bc as a calculator, proceed as follows:
Enter:
$ bc
1/4
The system responds as follows:
0
Enter:
scale = 1 /* Keep 1 decimal place */
1/4
The system responds as follows:
0.2
Enter:
scale = 3 /* Keep 3 decimal places */
1/4
The system responds as follows:
0.250
Enter:
16+63/5
The system responds as follows:
28.600
Enter:
(16+63)/5
The system responds as follows:
15.800
Enter:
71/6
The system responds as follows:
11.833
Enter:
1/6
The system responds as follows:
0.166
You may type the comments (enclosed in /* */), but they are provided
only for your information. The bc command displays the value of each
expression when you press <Return>, except for assignments.
2. To convert numbers from one base to another, proceed as follows:
Enter:
bc
obase = 16 /* Display numbers in Hexadecimal */
ibase = 8 /* Input numbers in Octal */
12
The system responds as follows:
A
Enter:
123
The system responds as follows:
53
Enter:
123456
The system responds as follows:
A72E
3. To write and run C-like programs, proceed as follows:
Create the following file prog.bc:
/* compute the factorial of n */
define f(n) {
auto i, r;
r = 1;
for (i=2; i<=n; i++) r =* i;
return (r);
}
Enter:
bc -l prog.bc
This interprets the bc program saved in prog.bc, then reads more bc
command statements from standard input (the keyboard). Starting the bc
command with the -l option makes the math library available. This
example uses the e (exponential) function from the math library, and f
is defined in the program prog.bc.
Enter:
e(2) /* e squared */
The system responds as follows:
7.38905609893065022723
Enter:
f(5) /* 5 factorial */
The system responds as follows:
120
Enter:
f(10) /* 10 factorial */
The system responds as follows:
3628800
The statement following a for or while statement must begin on the
same line.
4. To convert an infix expression to Reverse Polish Notation (RPN),
enter:
Enter:
bc -c
(a * b) % (3 + 4 * c)
The system responds as follows:
lalb* 3 4lc*+%ps.
This compiles the bc infix-notation expression into one that the dc
command can interpret. The dc command evaluates extended RPN
expressions. In the compiled output, the lowercase l before each
variable name is the dc subcommand to load the value of the variable
onto the stack. The p displays the value on top of the stack, and the
s. discards the top value by storing it in register . (dot). You can
save the RPN expression in a file for dc to evaluate later by
redirecting the standard output of this command.
ENVIRONMENT VARIABLES
The following environment variables affect the execution of bc:
LANG
Provides a default value for the internationalization variables that
are unset or null. If LANG is unset or null, the corresponding value
from the default locale is used. If any of the internationalization
variables contain an invalid setting, the utility behaves as if none of
the variables had been defined.
LC_ALL
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
LC_CTYPE
Determines the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multibyte characters in arguments).
LC_MESSAGES
Determines the locale for the format and contents of diagnostic
messages written to standard error.
NLSPATH
Determines the location of message catalogues for the processing of
LC_MESSAGES.
FILES
/usr/share/lib/lib.b
Mathematical library.
/usr/bin/dc
Desk calculator proper; uses bc as preprocessor.
SEE ALSO
Commands: awk(1), dc(1)
Standards: standards(5)
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Index for
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Alphabetical
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