bc - Provides a processor for arbitrary-precision arithmetic
language
bc [-cl] [file...]
The bc command is an interactive program that provides
unlimited precision arithmetic. It is a preprocessor for
the dc command.
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.
[Tru64 UNIX] Compiles file, but does not invoke dc.
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.
Pathname of a text file containing program statements.
After file has been exhausted, standard input is read.
[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 [Toc] [Back]
Comments are enclosed in /* and */.
Names [Toc] [Back]
Simple variables: letter
Array elements: letter[expression]
The words ibase, obase, and scale
Other Operands [Toc] [Back]
Arbitrarily long numbers with optional sign and decimal
point. Number of significant decimal digits Number of
digits to right of decimal point
Operators [Toc] [Back]
+ - * / % ^ (% is remainder; ^ is power)
++ -- (prefix and suffix; apply to names)
== <= >= != <>
= =+ =- =* =/ =% ^=
+= -= *= /= %=
Statements [Toc] [Back]
expression
{statement;...;statement}
if (expression) statement
while (expression) statement
for (expression;expression;expression) statement
(null statement)
break
quit
Function Definitions [Toc] [Back]
define letter ( letter,...,letter ) {
auto letter,...,letter
statement;...statement
return ( expression ) }
Functions in -l Math Library [Toc] [Back]
sine cosine exponential log arctangent Bessel function
General Syntax [Toc] [Back]
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.
The following exit values are returned: Successful completion.
An error occurred.
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. 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. 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 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. 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 [Toc] [Back] The following environment variables affect the execution
of bc: 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. If set to a non-empty
string value, overrides the values of all the other internationalization
variables. 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). Determines the locale for the
format and contents of diagnostic messages written to
standard error. Determines the location of message catalogues
for the processing of LC_MESSAGES.
Mathematical library. Desk calculator proper; uses bc as
preprocessor.
Commands: awk(1), dc(1)
Standards: standards(5)
bc(1)
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