expr(1B)					     SunOS/BSD Compatibility Package Commands						  expr(1B)

NAME

       expr - evaluate arguments as a logical, arithmetic, or string expression

SYNOPSIS

       /usr/ucb/expr argument...

DESCRIPTION

       The  expr utility evaluates expressions as specified by its arguments. After evaluation, the result is written on the standard output. Each
       token of the expression is a separate argument, so terms of the expression must be separated by blanks. Characters  special  to	the  shell
       must  be  escaped.  Note:  0  is returned to indicate a zero value, rather than the null string. Strings containing blanks or other special
       characters should be quoted. Integer-valued arguments may be preceded by a unary minus sign. Internally, integers are  treated  as  32-bit,
       two's-complement numbers.

       The  operators  and  keywords  are listed below. Characters that need to be escaped are preceded by `'. The list is in order of increasing
       precedence, with equal precedence operators grouped within {} symbols.

       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 lexical comparison.

       expr { +, - } expr

	   Addition or subtraction of integer-valued arguments.

       expr { , /, % } expr

	   Multiplication, division, or remainder of the integer-valued arguments.

       string : regular-expression
       match string regular-expression

	   The	two  forms  of	the matching operator above are synonymous. The matching operators : and match compare the first argument with the
	   second argument which must be a regular expression. Regular expression syntax is the same as that of regexp(5), except  that  all  pat-
	   terns  are  "anchored"  (treated  as  if  they begin with ^) and therefore ^ is not a special character, in that context. Normally, the
	   matching operator returns the number of characters matched (0 on failure). Alternatively, the ... pattern	symbols  can  be  used	to
	   return a portion of the first argument.

       substr string integer-1 integer-2

	   Extracts  the  substring of	string starting at position integer-1 and of length integer-2 characters. If integer-1 has a value greater
	   than the length of string, expr returns a null string. If you try to extract more characters than there are in string, expr returns all
	   the	remaining  characters from string. Beware of using negative values for either integer-1 or integer-2 as  expr tends to run forever
	   in these cases.

       index string character-list

	   Reports the first position in string at which any one of the characters in character-list matches a character in  string.

       length string

	   Returns the length (that is, the number of characters) of string.

       ( expr )

	   Parentheses may be used for grouping.

EXAMPLES

       Example 1 Adding an integer to a shell variable

       Add 1 to the shell variable a.

	 a='expr $a + 1'

       Example 2 Returning a path name segment

       Return the last segment of a path name (that is, the filename part). Watch out for / alone as an argument: expr will take it as	the  divi-
       sion operator (see BUGS below).

	 # 'For $a equal to either "/usr/abc/file" or just "file"'
	 expr  $a  :  '.*/  	$a

       Example 3 Using // characters to simplify the expression

       The addition of the // characters eliminates any ambiguity about the division operator and simplifies the whole expression.

	 # A better representation of example 2.
	 expr  //$a  :	'.*/

       Example 4 Returning the value of a variable

       Returns the number of characters in $VAR.

	 expr  $VAR  :	'.*'

EXIT STATUS

       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.

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWscpu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sh(1), test(1), attributes(5), regexp(5)

DIAGNOSTICS

       syntax error	       for operator/operand errors

       non-numeric argument    if arithmetic is attempted on such a string

       division by zero        if an attempt to divide by zero is made

BUGS

       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:

	 expr  $a  =  '='

       looks like:

	 expr  =  =  =

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

	 expr  X$a  =  X=

       Note: the match, substr, length, and index operators cannot themselves be used as ordinary strings.  That is, the expression:

	 example% expr index expurgatorious length
	 syntax error
	 example%

       generates the `syntax error' message as shown instead of the value 1 as you might expect.

SunOS 5.11							    6 Jun 2000								  expr(1B)