EXPR(1) EXPR(1) NAME expr - evaluate arguments as an expression SYNOPSIS expr arg ... DESCRIPTION The arguments are taken as an expression. After evaluation, the result is written on the standard output. Each token of the expression is a separate argument. The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped. _e_x_p_r _| _e_x_p_r yields the first _e_x_p_r if it is neither null nor ‘0’, otherwise yields the second _e_x_p_r_. _e_x_p_r _& _e_x_p_r yields the first _e_x_p_r if neither _e_x_p_r is null or ‘0’, otherwise yields ‘0’. _e_x_p_r _r_e_l_o_p _e_x_p_r where _r_e_l_o_p _i_s _o_n_e _o_f < <= = != >= >, yields ‘1’ if the indi‐ cated comparison is true, ‘0’ if false. The comparison is numeric if both _e_x_p_r are integers, otherwise lexicographic. _e_x_p_r + _e_x_p_r _e_x_p_r - _e_x_p_r addition or subtraction of the arguments. _e_x_p_r * _e_x_p_r _e_x_p_r / _e_x_p_r _e_x_p_r % _e_x_p_r multiplication, division, or remainder of the arguments. _e_x_p_r : _e_x_p_r The matching operator compares the string first argument with the regular expression second argument; regular expression syn‐ tax is the same as that of _e_d(1). The \(...\) pattern symbols can be used to select a portion of the first argument. Other‐ wise, the matching operator yields the number of characters matched (‘0’ on failure). ( _e_x_p_r ) parentheses for grouping. Examples: To add 1 to the Shell variable _a: a=`expr $a + 1` To find the filename part (least significant part) of the pathname stored in variable _a_, which may or may not contain ‘/’: expr $a : ´.*/\(.*\)´ ´|´ $a Note the quoted Shell metacharacters. SEE ALSO sh(1), test(1) DIAGNOSTICS _E_x_p_r returns the following exit codes: 0 if the expression is neither null nor ‘0’, 1 if the expression is null or ‘0’, 2 for invalid expressions. 7th Edition April 29, 1985 EXPR(1)