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 BCDIMAX dimensions).
The words ibase, obase (limited to BCBASEMAX), and scale
(limited to BCSCALEMAX).
Other Operands
Arbitrarily long numbers with optional sign and decimal
point. Strings of fewer than BCSTRINGMAX characters,
between double quotes ("). ( E )
sqrt ( E ) Square root
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User Commands bc(1)
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 )
}
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User Commands bc(1)
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 fol-
low 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
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User Commands bc(1)
-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
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User Commands bc(1)
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(5) for descriptions of the following environment
variables that affect the execution of bc: LANG, LCAL,
LCTYPE, LCMESAGES, 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
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
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User Commands bc(1)
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWesu
Interface Stability Standard
SEE ALSO
dc(1), awk(1), attributes(5), environ(5), standards(5)
NOTES
The bc command does not recognize the logical operators &&
and .
The for statement must have all three expressions (E's).
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