expr man page on Solaris

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

NAME
       expr  -	evaluate arguments as a logical, arithmetic, or string expres‐
       sion

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 expres‐
       sion  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-comple‐
       ment numbers.

       The operators and keywords are listed below. Characters that need to be
       escaped	are preceded by `\'. The list is in order of increasing prece‐
       dence, 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	 argu‐
	   ments.

       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 expres‐
	   sion syntax is the same as that of regexp(5), except that all  pat‐
	   terns  are  "anchored" (treated as if they begin with ^) and there‐
	   fore ^ 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 char‐
	   acters 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 division
       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 5.10			  6 Jun 2000			      expr(1B)
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