bc

Additional Notes

bc is a calculator language for arbitrary precision arithmetic. It is useful in shell scripts because POSIX shell arithmetic only handles integers.

Use bc for decimal math, larger calculations, and quick terminal calculations.

Syntax

bc [options] [file...]

Parameters

• file: Optional file containing bc expressions.
• expression: Math expression read from standard input.
• options: Math library and mode flags.

Common Options

• -l: Load the standard math library and set a useful default scale.
• -q: Quiet mode. Do not print the startup banner.
• -s: Standard POSIX mode.
• -w: Warn about non-standard extensions.

Examples

echo "2 + 3" | bc

Add numbers.

echo "scale=2; 10 / 3" | bc

Divide with two decimal places.

echo "sqrt(81)" | bc -l

Use the math library.

result=$(echo "scale=4; $used / $total * 100" | bc)

Use bc in a shell script.

Practical Notes

• Set scale when you need decimal division.
• Use bc -l for functions such as sqrt and trigonometry.
• Validate variables before inserting them into expressions in scripts.