fmlexpr(1F)                      UNIX System V                      fmlexpr(1F)


NAME
      fmlexpr - evaluate arguments as an expression

SYNOPSIS
      fmlexpr arguments

DESCRIPTION
      The fmlexpr function evaluates its arguments 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 FMLI 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 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
           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.

EXAMPLES




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fmlexpr(1F)                      UNIX System V                      fmlexpr(1F)


      1.    Add 1 to the variable a:

                  `fmlexpr $a + 1 | set -l a`

      2.    For $a equal to either ``/usr/abc/file'' or just ``file'':

                  fmlexpr  $a  :  .*/\(.*\)  \|  $a

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

      3.    A better representation of example 2.

                  fmlexpr  //$a  :  .*/\(.*\)

      The addition of the // characters eliminates any ambiguity about the
      division operator (because it makes it impossible for the left-hand
      expression to be interpreted as the division operator), and simplifies
      the whole expression.

      4.    Return the number of characters in $VAR.

                  fmlexpr $VAR : .*

DIAGNOSTICS
      As a side effect of expression evaluation, fmlexpr returns the following
      exit values:
            0     if the expression is neither null nor 0 (i.e., TRUE)
            1     if the expression is null or 0 (i.e., FALSE)
            2     for invalid expressions (i.e., FALSE).

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

      In the case of syntax errors and non-numeric arguments, an error message
      will be printed at the current cursor position.  Use refresh to redraw
      the screen.

NOTES
      After argument processing by FMLI, fmlexpr cannot tell the difference
      between an operator and an operand except by the value.  If $a is an =,
      the command:

            fmlexpr  $a  =  =

      looks like:

            fmlexpr  =  =  =




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fmlexpr(1F)                      UNIX System V                      fmlexpr(1F)


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

            fmlexpr  X$a  =  X=

SEE ALSO
      ed(1), expr(1), set(1F), sh(1)















































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