expr(1) 							   User Commands							   expr(1)

NAME

       expr - evaluate arguments as an expression

SYNOPSIS

       /usr/bin/expr argument...

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

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

DESCRIPTION

   /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.

   /usr/xpg6/bin/expr
       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.

OPERANDS

       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  lim-
       ited 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 comparison 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 arguments.

       expr : expr

	   The	matching operator : (colon) compares the first argument with the second argument, which must be an internationalized basic regular
	   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 operator
	   returns the number of bytes matched and the /usr/xpg4/bin/expr matching operator returns the number of characters matched (0  on  fail-
	   ure). If the second argument contains at least one BRE sub-expression [(...)], the matching operator returns the string corresponding
	   to 1.

       integer

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

       string

	   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-  INTERAC-
       TIVE UNIX System scripts:

       index string character-list

	   Report the first position in which any one of the bytes in character-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.

EXAMPLES

       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 : '.*/(.*)'

   /usr/bin/expr
       Example 4: Returning the number of bytes in a variable

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

   /usr/xpg4/bin/expr
       Example 5: Returning the number of characters in a variable

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

ENVIRONMENT VARIABLES

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

EXIT STATUS

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

       0	If the expression is neither NULL nor 0.

       1	If the expression is either NULL or 0.

       2	For invalid expressions.

       >2	An error occurred.

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |enabled			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

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

DIAGNOSTICS

       syntax error	       Operator and operand errors.

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

NOTES

       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 Regular Expressions for all system-provided locales. Internationalized
       Regular Expressions are explained on the regex(5) manual page.

SunOS 5.10							    29 Aug 2003 							   expr(1)