expr man page on UNIXv7

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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	 indi‐
	      cated  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
	      The matching operator compares the string	 first	argument  with
	      the  regular expression second argument; regular expression syn‐
	      tax is the same as that of ed(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).

       ( 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
       ed(1), 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.

								       EXPR(1)
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