


      EEEEXXXXPPPPRRRR((((1111))))                     ((((UUUUNNNNIIIIXXXX 5555....0000))))                    EEEEXXXXPPPPRRRR((((1111))))



      NNNNAAAAMMMMEEEE
           expr - evaluate arguments as an expression

      SSSSYYYYNNNNTTTTAAAAXXXX
           eeeexxxxpppprrrr arguments

      DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
           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 0000 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.  Characters
           that need to be escaped are preceded by \\\\.  The list is in
           order of increasing precedence, with equal precedence
           operators grouped within {{{{}}}} symbols.

           _e_x_p_r \\\\|||| _e_x_p_r
                returns the first _e_x_p_r if it is neither null nor 0000,
                otherwise returns the second _e_x_p_r.

           _e_x_p_r \\\\&&&& _e_x_p_r
                returns the first _e_x_p_r if neither _e_x_p_r is null or 0000,
                otherwise returns 0000.

           _e_x_p_r { ====, \\\\>>>>, \\\\>>>>====, \\\\<<<<, \\\\<<<<====, !!!!==== } _e_x_p_r
                returns the result of an integer comparison if both
                arguments are integers, otherwise returns the result of
                a lexical comparison.

           _e_x_p_r { ++++, ---- } _e_x_p_r
                addition or subtraction of integer-valued arguments.

           _e_x_p_r { \\\\****, ////, %%%% } _e_x_p_r
                multiplication, division, or remainder of the integer-
                valued arguments.

           _e_x_p_r :::: _e_x_p_r
                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 _e_d(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 characters
                matched (0000 on failure).  Alternatively, the \\\\((((............\\\\))))
                pattern symbols can be used to return a portion of the



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                first argument.

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

                     adds 1 to the shell variable aaaa.

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

                     returns the last segment of a path name (i.e.,
                     file).  Watch out for //// alone as an argument:
                     _e_x_p_r will take it as the division operator (see
                     BUGS below).

           3.   ####  A better representation of example 2.
                expr  //$a  ::::  '....*/\(....*\)'

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

           4.   expr  $VAR  ::::  '....****'

                     returns the number of characters in $$$$VVVVAAAARRRR.

      SSSSEEEEEEEE AAAALLLLSSSSOOOO
           ed(1), sh(1).

      EEEEXXXXIIIITTTT CCCCOOOODDDDEEEE
           As a side effect of expression evaluation, _e_x_p_r returns the
           following exit values:
                0    if the expression is neither null nor 0000
                1    if the expression _i_s null or 0000
                2    for invalid expressions.

      DDDDIIIIAAAAGGGGNNNNOOOOSSSSTTTTIIIICCCCSSSS
           _s_y_n_t_a_x _e_r_r_o_r   for operator/operand errors
           _n_o_n-_n_u_m_e_r_i_c _a_r_g_u_m_e_n_t
                          if arithmetic is attempted on such a string

      BBBBUUUUGGGGSSSS
           After argument processing by the shell, _e_x_p_r cannot tell the
           difference between an operator and an operand except by the
           value.  If $$$$aaaa is an ====, the command:

                expr  $a  =  '='

           looks like:

                expr  =  =  =



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

                expr  X$a  =  X=



















































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