expr(1) - SerenityOS man pages

Name

expr - evaluate expressions

$ expr <expression>
$ expr [--help]

expr evaluates and prints the result of an expression as described below to standard output.

An expression may be any of the following:

expr1 | expr2 expr2 if expr1 is falsy, expr1 otherwise.
expr1 & expr2 expr1 if neither expression is falsy, 0 otherwise.
expr1 < expr2 1 if expr1 is less than expr2, 0 otherwise.
expr1 <= expr2 1 if expr1 is less than or equal to expr2, 0 otherwise.
expr1 = expr2 1 if expr1 is equal to expr2, 0 otherwise.
expr1 = expr2 1 if expr1 is not equal to expr2, 0 otherwise.
expr1 => expr2 1 if expr1 is greater than or equal to expr2, 0 otherwise.
expr1 > expr2 1 if expr1 is greater than expr2, 0 otherwise.
expr1 + expr2 arithmetic integral sum of expr1 and expr2.
expr1 - expr2 arithmetic integral difference of expr1 and expr2.
expr1 * expr2 arithmetic integral product of expr1 and expr2.
expr1 / expr2 arithmetic integral quotient of expr1 divided by expr2.
expr1 % expr2 arithmetic integral quotient of expr1 divided by expr2.
expr1 : expr2 pattern match of expr2 as a regular expression in expr1 - currently not implemented.
match expr1 expr2 same as expr1 : expr2.
substr expr1 expr2 expr3 substring with length expr3 of expr1, starting at expr2, indices starting at 1.
index expr1 expr2 index of expr2 in expr1, starting at 1. 0 if not found.
length expr1 length of the string expr1
+ token interpret token as a string, regardless of whether it is a keyword or an operator.
( expr ) value of expr

Note that many operators will need to be escaped or quoted if used from within a shell. "falsy" means either the number 0, or the empty string.

$ expr 1 + 2 * 3          # = 7
$ expr \( 1 + 2 \) = 3    # = 1
$ expr substr foobar 1 3  # foo