4.3BSD-UWisc/man/cat1/expr.1

EXPR(1)             UNIX Programmer's Manual              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 opera-
     tors 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
          indicated comparison is true, `0' if false.  The com-
          parison 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 argu-
          ments.

     _e_x_p_r : _e_x_p_r
          The matching operator compares the string first argu-
          ment with the regular expression second argument; regu-
          lar expression syntax is the same as that of _e_d(1).
          The \(...\) pattern symbols can be used to select a
          portion of the first argument.  Otherwise, the matching
          operator yields the number of characters matched (`0'
          on failure).

     ( _e_x_p_r )
          parentheses for grouping.





Printed 12/27/86         April 29, 1985                         1






EXPR(1)             UNIX Programmer's Manual              EXPR(1)



     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.
































Printed 12/27/86         April 29, 1985                         2