EXPR(C)                  XENIX System V                   EXPR(C)



     Name
          expr - Evaluates arguments as an expression.

     Syntax
          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 zero 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, 2's
          complement numbers.

          The operators and keywords are listed below.  Expressions
          should be quoted by the shell, since many of the characters
          that have special meaning in the shell also have special
          meaning in expr. The list is in order of increasing
          precedence, with equal precedence operators grouped within
          braces ({ and }).

          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 nor 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(C), except that all patterns are
               ``anchored'' (i.e., begin with a caret (^)) and
               therefore the caret is not a special character in that
               context.  (Note that in the shell, the caret has the



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     EXPR(C)                  XENIX System V                   EXPR(C)



               same meaning as the pipe symbol (|).) Normally the
               matching operator returns the number of characters
               matched (zero on failure).  Alternatively, the \(...\)
               pattern symbols can be used to return a portion of the
               first argument.

     Examples
          1.   a=`expr $a + 1`

                    Adds 1 to the shell variable a.

          2.   #  'For $a equal to either "/usr/abc/file" or just
               "/file"'
               'expr  $a  :  '.*/\(.*\)'  |  $a'

                    Returns the last segment of a pathname (i.e.,
                    file).  Watch out for the slash alone as an
                    argument: expr will take it as the division
                    operator (see Notes on the next page).

          3.   expr  $VAR  :  '.*'

                    Returns the number of characters in $VAR.

     See Also
          ed(C), sh(C)

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

               0    If the expression is neither null nor zero
               1    If the expression is null or zero
               2    For invalid expressions

          Other diagnostics include:

          syntax error   For operator/operand errors

          nonnumeric argument
                         If arithmetic is attempted on such a string














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     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 equals sign (=), the command:

               expr  $a  =  '='

          looks like:

               expr  =  =  =

          Thus the arguments are passed to expr (and will all be taken
          as the = operator).  The following permits comparing equals
          signs:

               expr  X$a  =  X=







































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