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 opera-
          tors grouped.

          expr | expr
               yields the first expr if it is neither null nor `0',
               otherwise yields the second expr.

          expr & expr
               yields the first expr if neither expr is null or `0',
               otherwise yields `0'.

          expr relop expr
               where relop is one of < <= = != >= >, yields `1' if the
               indicated comparison is true, `0' if false.  The com-
               parison is numeric if both expr are integers, otherwise
               lexicographic.

            expr
            expr
               addition or subtraction of the arguments.

            expr
            expr
            expr
               multiplication, division, or remainder of the argu-
               ments.

            expr
               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 ed(1). The
               \(...\) pattern symbols can be used to select a portion
               of the first argument.  Otherwise, the matching opera-
               tor yields the number of characters matched (`0' on
               failure).

          ( expr )
               parentheses for grouping.

     EXPR(1)                                                   EXPR(1)

     EXAMPLES
          a=`expr $a + 1`
               Add 1 to shell variable a.

          expr $a : '.*/(.*)' '|' $a
               Find the filename part (least significant part) of
               pathname a, which may or may not contain `/'.  Note the
               quoted shell metacharacters.

     SEE ALSO
          sh(1), test(1)

     DIAGNOSTICS
          Expr 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.