
bc(1) 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 con
straints 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 out
put instead.
USAGE
The syntax for bc programs is as follows:
L Means a letter az,
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 newlines 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.
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 
+++
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).
SunOS 5.11 29 Aug 2003 bc(1) 
