expr(1)                        DG/UX 5.4R3.00                        expr(1)


NAME
       expr - evaluate arguments as an expression

SYNOPSIS
       expr arguments

DESCRIPTION
       The arguments are taken as an expression.  After evaluation, the
       result is written on the standard output.  Terms of the expression
       must be separated by blanks.  Characters special to the shell must be
       escaped.  Note that 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, 2s complement numbers.  The length of the expression is
       limited to 512 characters.

       The operators and keywords are listed below.  Characters that need to
       be escaped in the shell [see sh(1)] are preceded by \.  The list is
       in order of increasing precedence, with equal precedence operators
       grouped within {} symbols.

       expr \| expr
            returns the first expr if it is neither null nor 0, otherwise
            returns the second expr.

       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.

       expr : expr
            The matching operator : compares the first argument with the
            second argument, which must be a regular expression.  Regular
            expression syntax is the same as that of ed(1), except that all
            patterns are ``anchored'' (i.e., begin with ^) and, therefore, ^
            is not a special character, in that context.  Normally, the
            matching operator returns the number of bytes matched (0 on
            failure).  Alternatively, the \(...\) pattern symbols can be
            used to return a portion of the first argument.

   International Features
       expr can process characters from supplementary code sets in addition



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expr(1)                        DG/UX 5.4R3.00                        expr(1)


       to ASCII characters.  In regular expressions, pattern searches are
       performed on characters, not bytes.

EXAMPLES
       Add 1 to the shell variable a (assuming a is set to an integer
       value):

              a=`expr $a + 1`

       The following example emulates basename(1)--it returns 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 the NOTES below.)

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

       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.

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

       Return the number of characters in $VAR:

              expr $VAR : '.*'

DIAGNOSTICS
       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 null or 0
            2    for invalid expressions.

        syntax error     for operator/operand errors
        non-numeric argument
                         if arithmetic is attempted on such a string

SEE ALSO
       ed(1), sh(1).

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:

              expr $a = '='

       looks like:

              expr = = =

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



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expr(1)                        DG/UX 5.4R3.00                        expr(1)


              expr X$a = X=
























































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