expr(1)                                                   expr(1)



NAME
     expr - evaluates arguments as an expression

SYNOPSIS
     expr arguments

ARGUMENTS
     arguments
          Specifies the arguments to be evaluated.

DESCRIPTION
     expr evaluates its arguments as an expression and writes the
     result on the standard output.  Terms of the expression must
     be separated by blanks.  Characters special to the Bourne
     shell or Korn shell (sh(1) or ksh(1), respectively) must be
     escaped.  (The expr command is replaced in the C shell
     (csh(1)) by @.)  Note that 0 is returned to indicate a zero
     value, rather than the null string.  Strings containing
     blanks or other special characters should be enclosed in
     quotation marks.  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.  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 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
          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),



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expr(1)                                                   expr(1)



          except that all patterns are anchored (that is, 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.

EXAMPLES
          a=`expr $a + 1`

     adds 1 to the shell variable a.

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

     returns the last segment of a pathname (that is, file).
     Watch out for / alone as an argument:  expr will take it as
     the division operator (see the ``Limitations'' section later
     in this manual page).

     A better representation of the preceding example:

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

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

          expr $VAR  :  '.*'

     returns the number of characters in $VAR.

STATUS MESSAGES AND VALUES
     syntax error
          for operator/operand errors

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

     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

LIMITATIONS
     After argument processing by the shell, expr cannot tell the
     difference between an operator and an operand except by the



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expr(1)                                                   expr(1)



     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=


FILES
     /bin/expr
          Executable file

SEE ALSO
     csh(1), ed(1), ksh(1), sh(1)



































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