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EXPR(1)								       EXPR(1)

       expr - evaluate arguments as an expression

       /usr/bin/expr argument...

       /usr/xpg4/bin/expr argument...

       /usr/xpg6/bin/expr argument...

   /usr/bin/expr, /usr/xpg4/bin/expr
       The  expr  utility  evaluates  the  expression and writes the result to
       standard output. The character 0 is written to indicate	a  zero	 value
       and nothing is written to indicate a null string.

       The  expr  utility  evaluates  the  expression and writes the result to
       standard output followed by a NEWLINE. If there is no result from  expr
       processing, a NEWLINE is written to standard output.

       The  argument  operand  is  evaluated  as  an  expression. Terms of the
       expression must be separated by blanks. Characters special to the shell
       must be escaped (see sh(1)). Strings containing blanks or other special
       characters should be quoted. The length of the expression is limited to
       LINE_MAX (2048 characters).

       The  operators  and  keywords are listed below. The list is in order of
       increasing precedence, with equal precedence operators  grouped	within
       {} symbols.  All of the operators are left-associative.

       expr \| expr

	   Returns  the evaluation of the first expr if it is neither NULL nor
	   0; otherwise, returns the evaluation of the second expr  if	it  is
	   not NULL; otherwise, 0.

       expr \& expr

	   Returns  the	 first	expr  if  neither expr is NULL or 0, otherwise
	   returns 0.

       expr{ =, \>, \>=, \<, \<=, !=} expr

	   Returns the result of an integer comparison if both	arguments  are
	   integers, otherwise returns the result of a string comparison using
	   the locale-specific coalition sequence. The result of each compari‐
	   son will be 1 if the specified relationship is TRUE, 0 if the rela‐
	   tionship is FALSE.

       expr { +, − } expr

	   Addition or subtraction of integer-valued arguments.

       expr { \*, /, %} expr

	   Multiplication, division, or remainder of the integer-valued	 argu‐

       expr : expr

	   The	matching  operator  : (colon) compares the first argument with
	   the second argument, which must be an internationalized basic regu‐
	   lar	expression (BRE), except that all patterns are anchored to the
	   beginning of the string.  That is, only sequences starting  at  the
	   first  character of a string are matched by the regular expression.
	   See regex(5) and NOTES. Normally, the /usr/bin/expr matching opera‐
	   tor	returns the number of bytes matched and the /usr/xpg4/bin/expr
	   matching operator returns the number of characters  matched	(0  on
	   failure).  If  the  second  argument contains at least one BRE sub-
	   expression [\(...\)], the matching operator returns the string cor‐
	   responding to \1.


	   An  argument	 consisting only of an (optional) unary minus followed
	   by digits.


	   A string argument that cannot be identified as an integer  argument
	   or as one of the expression operator symbols.

   Compatibility Operators (x86 only)
       The following operators are included for compatibility with INTERACTIVE
       UNIX System only and are not intended to be used	 by  non-  INTERACTIVE
       UNIX System scripts:

       index string character-list

	   Report  the first position in which any one of the bytes in charac‐
	   ter-list matches a byte in string.

       length string

	   Return the length (that is, the number of bytes) of string.

       substr string integer-1 integer-2

	   Extract the substring of string starting at position integer-1  and
	   of  length  integer-2 bytes.	 If integer-1 has a value greater than
	   the number of bytes in string, expr returns a null string.  If  you
	   try	to  extract  more bytes than there are in string, expr returns
	   all the remaining bytes from string.	 Results  are  unspecified  if
	   either integer-1 or integer-2 is a negative value.

       Example 1 Adding an integer to a shell variable

       Add 1 to the shell variable a:

	 example$ a=`expr $a + 1`

       Example 2 Returning a path name segment

       The  following example emulates basename(1), returning the last segment
       of the path name $a. For $a equal to either /usr/abc/file or just file,
       the  example  returns file. (Watch out for / alone as an argument: expr
       takes it as the division operator. See NOTES below.)

	 example$ expr $a : '.*/\(.*\)' \| $a

       Example 3 Using // characters to simplify the expression

       Here is a better version of the previous example. The addition  of  the
       //  characters eliminates any ambiguity about the division operator and
       simplifies the whole expression.

	 example$ expr //$a : '.*/\(.*\)'

       Example 4 Returning the number of bytes in a variable

	 example$ expr "$VAR" : '.*'

       Example 5 Returning the number of characters in a variable

	 example$ expr "$VAR" : '.*'

       See environ(5) for descriptions of the following environment  variables
       that  affect the execution of expr: LANG, LC_ALL, LC_COLLATE, LC_CTYPE,

       As a side effect of expression evaluation, expr returns	the  following
       exit values:

	      If the expression is neither NULL nor 0.

	      If the expression is either NULL or 0.

	      For invalid expressions.

	      An error occurred.

       See attributes(5) for descriptions of the following attributes:

       │CSI		    │ enabled	      │
       │Interface Stability │ Standard	      │

       basename(1),   ed(1),   sh(1),	Intro(3),  attributes(5),  environ(5),
       regex(5), standards(5)

       syntax error
			       Operator and operand errors.

       non-numeric argument
			       Arithmetic is attempted on such a string.

       After argument processing by the shell, expr cannot tell the difference
       between	an operator and an operand except by the value. If $a is an =,
       the command:

	 example$ expr $a = '='

       looks like:

	 example$ expr = = =

       as the arguments are passed to expr (and they are all taken  as	the  =
       operator). The following works:

	 example$ expr X$a = X=

   Regular Expressions
       Unlike  some previous versions, expr uses Internationalized Basic Regu‐
       lar Expressions for all system-provided locales. Internationalized Reg‐
       ular Expressions are explained on the regex(5) manual page.

				 Aug 29, 2003			       EXPR(1)

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