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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.

       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 comparison is
	      numeric if both expr are integers, otherwise lexicographic.

       expr + expr
       expr - expr
	      addition or subtraction of the arguments.

       expr * expr
       expr / expr
       expr % expr
	      multiplication, division, or remainder of the arguments.

       expr : expr
       match expr expr
	      compares the first argument (a string) with the second  argument
	      (a regular expression); regular 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,  this
	      operator	yields	the  number  of	 characters  matched  (`0'  on
	      failure).

       index expr expr
	      finds  the second argument (a string) in the first.  Returns the
	      location	of  the	 first	matched	 character  (where  the	 first
	      character	 is  at location `1') or `0' if the second argument is
	      not a substring of the first.

       substr expr expr expr
	      returns the substring of the  first  argument  (a	 string)  that
	      starts  at  the position specified by the second argument (where
	      `1' refers to the first character) and has length equal  to  the
	      third argument (a numeral).

       length expr
	      returns the length of the argument (a string).

       ( expr )
	      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
       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.

7th Edition			April 29, 1985			       EXPR(1)

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