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Unix Version 7 - man page for expr (v7 section 1)

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EXPR(1) 										  EXPR(1)

       expr - evaluate arguments as an expression

       expr arg ...

       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  prece-
       dence, with equal precedence operators grouped.

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

       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

       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  expres-
	      sion  second argument; 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,  the  matching  operator yields the number of characters matched (`0' on

       ( expr )
	      parentheses for grouping.


       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.

       ed(1), sh(1), test(1)

       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.

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