expr(1) [opendarwin man page]

EXPR(1) 						    BSD General Commands Manual 						   EXPR(1)

NAME

     expr -- evaluate expression

SYNOPSIS

     expr expression

DESCRIPTION

     The expr utility evaluates expression and writes the result on standard output.

     All operators are separate arguments to the expr utility.	Characters special to the command interpreter must be escaped.

     Operators are listed below in order of increasing precedence.  Operators with equal precedence are grouped within { } symbols.

     expr1 | expr2
	     Returns the evaluation of expr1 if it is neither an empty string nor zero; otherwise, returns the evaluation of expr2.

     expr1 & expr2
	     Returns the evaluation of expr1 if neither expression evaluates to an empty string or zero; otherwise, returns zero.

     expr1 {=, >, >=, <, <=, !=} expr2
	     Returns the results of integer comparison if both arguments are integers; otherwise, returns the results of string comparison using
	     the locale-specific collation sequence.  The result of each comparison is 1 if the specified relation is true, or 0 if the relation
	     is false.

     expr1 {+, -} expr2
	     Returns the results of addition or subtraction of integer-valued arguments.

     expr1 {*, /, %} expr2
	     Returns the results of multiplication, integer division, or remainder of integer-valued arguments.

     expr1 : expr2
	     The ``:'' operator matches expr1 against expr2, which must be a regular expression.  The regular expression is anchored to the begin-
	     ning of  the string with an implicit ``^''.  expr expects "basic" regular expressions, see re_format(7) for more information on regu-
	     lar expressions.

	     If the match succeeds and the pattern contains at least one regular expression subexpression ``(...)'', the string corresponding to
	     ``1'' is returned; otherwise the matching operator returns the number of characters matched.  If the match fails and the pattern
	     contains a regular expression subexpression the null string is returned; otherwise 0.

     Parentheses are used for grouping in the usual manner.

EXAMPLES

     1.   The following example adds one to the variable a.
		a=`expr $a + 1`

     2.   The following example returns the filename portion of a pathname stored in variable a.  The // characters act to eliminate ambiguity
	  with the division operator.
		expr //$a : '.*/(.*)'

     3.   The following example returns the number of characters in variable a.
		expr $a : '.*'

DIAGNOSTICS

     The expr utility exits with one of the following values:
     0	     the expression is neither an empty string nor 0.
     1	     the expression is an empty string or 0.
     2	     the expression is invalid.

STANDARDS

     The expr utility conforms to IEEE Std 1003.2 (``POSIX.2'').

BSD
								   July 3, 1993 							       BSD

Check Out this Related Man Page

EXPR(1) 						      General Commands 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 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
	      The  matching  operator compares the string first argument with the regular expression 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 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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expr(1) [opendarwin man page]

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