bc - arbitrary precision arithmetic language
/usr/bin/bc [-c] [-l] [file]...
/usr/xpg6/bin/bc [-c] [-l] [file]...
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.
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.
Simple variables: L.
Array elements: L [ E ] (up to BC_DIM_MAX dimensions).
The words ibase, obase (limited to BC_BASE_MAX), and
scale (limited to BC_SCALE_MAX).
Arbitrarily long numbers with optional sign and decimal point. Strings of fewer
than BC_STRING_MAX characters, between double quotes ("). (
E )
sqrt ( E )
Square root
length ( E )
Number of significant decimal digits.
scale ( E )
Number of digits right of decimal point.
L ( E , ... , E )
+ − * / % ^
(% is remainder; ^ is power)
++ −−
(prefix and postfix; apply to names)
== <= >= != < >
= =+ =− =* =/ =% =^
E
{ S ;... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit
.string
define L ( L ,..., L ) {
auto L ,..., L
S ;... S
return ( E )
}
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 follow the array name.
The following operands are supported:
-c
Compiles only. The output is dc commands that are
sent to the standard output.
-l
Defines the math functions and initializes scale
to 20, instead of the default zero.
-l
Defines the math functions and initializes scale
to 20, instead of the default zero. All math results have the scale of
20.
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.
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
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) }
See environ(5) for descriptions of the following environment variables
that affect the execution of bc: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.
The following exit values are returned:
0
All input files were processed successfully.
unspecified
An error occurred.
/usr/lib/lib.b
mathematical library
/usr/include/limits.h
to define BC_ parameters
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE
TYPE |
ATTRIBUTE VALUE |
| Interface Stability |
Standard |
dc(1), awk(1), attributes(5), environ(5),
standards(5)
The bc command does not recognize the logical operators &&
and ||.
The for statement must have all three expressions
(E's).