BC(1)BC(1)NAMEbc - 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 BC_DIM_MAX dimensions).
The words ibase, obase (limited to BC_BASE_MAX), and scale (limited
to BC_SCALE_MAX).
Other Operands
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 )
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 )
}
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 sep‐
arate statements. Assignment to scale influences the number of digits
to be retained on arithmetic operations in the manner of dc. Assign‐
ments to ibase or obase set the input and output number radix respec‐
tively.
The same letter may be used as an array, a function, and a simple vari‐
able simultaneously. All variables are global to the program. auto
variables are stacked during function calls. When using arrays as func‐
tion arguments or defining them as automatic variables, empty square
brackets must follow 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
-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
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, LC_ALL, LC_CTYPE, LC_MESSAGES,
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
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
└────────────────────┴─────────────────┘
SEE ALSOdc(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).
Aug 29, 2003 BC(1)
