3.4 Boolean Expressions ======================= Boolean operations are also legal. (POSIX 'bc' does NOT have boolean operations). The result of all boolean operations are 0 and 1 (for false and true) as in relational expressions. The boolean operators are: '!expr' The result is 1 if expr is 0. 'expr && expr' The result is 1 if both expressions are non-zero. 'expr || expr' The result is 1 if either expression is non-zero.