Arithmetic evaluation (command)

(( <EXPRESSION> ))

This command evaluates the arithmetic expression <EXPRESSION>.

If the expression evaluates to 0 then the exit code of the expression is set to 1 (FALSE). If the expression evaluates to something else than 0, then the exit code of the expression is set to 0 (TRUE).
This is done to map the arithmetic “true” and “false” to the shell exit codes for TRUE and FALSE.

• Internal: arithmetic expressions
• Internal: arithmetic expansion