bc - Basic Calculator

References

• Command Manual

Truth

Relational expressions return 0 if the relation is false and 1 if the relation is true
Any non-zero result is considered true.
but beware of precedence. a = 3 < 2 does not assign 1 to a; instead it sets a = 3 and then compares 3 to 2 so to get the same result as in c, use parenthesis a = ( 3 < 2 )

Math Library Functions

• s(x) - The sine of x, x is in radians.
• c(x) - The cosine of x, x is in radians.
• a(x) - The arctangent of x, arctangent returns radians.
• l(x) - The natural logarithm of x.
• e(x) - The exponential function of raising e to the value x.
• j(n,x) - The bessel function of integer order n of x.

bc must be called with the parameter -l in order to use the math library.
This also sets the default scale to 20.

$ echo '4*a(1)' | bc
Runtime error (func=(main), adr=3): Function a not defined.

$ echo '4*a(1)' | bc -l
3.14159265358979323844

echo 'scale=50;4*a(1)'|bc -l
3.14159265358979323846264338327950288419716939937508

Note that the precision for pi suffers in the last 1-2 decimal places so for a work around, ask for two more than you want and truncate.

Scripting

#!/usr/bin/bc -ql
# Two comment styles:
/* also this */
"How old are you ? "
age = read()
print age
" isn't very old"
print "\n"
halt

Only numbers can be input using read

Functions

Functions return 0 (false) by default.
Assume this script is named factorial

#!/usr/bin/bc -q
# Recursion is possible
define f (x) {
if (x <= 1) return (1);
return (f(x-1) * x);
}

f(8)
halt

$ factorial
40320

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	First created Feb 5, 2010 ~ Last revised February 05, 2010