     GEXPR(1)                        GEXPR 2.0.2                        GEXPR(1)
                                      May 2001

     NAME
          gexpr - handy shell calculator

     SYNOPSIS
          gexpr [ options ] expression

     DESCRIPTION
          gexpr is an expression parser that can be used as a simple command-
          line calculator, as in gexpr 'sin(pi/4)*sqrt(4)', or to add floating
          point math to shell scripts. It is meant to be an alternative to bc
          (1), being less powerful but lighter and much more intuitive. It also
          provides a few nice features of its own.

          If an expression is given as argument, it must be protected from the
          shell using quotes as in the example above. If you fail to do so,
          parentheses will be interpreted and the * character will be expanded
          by the shell, wreaking havoc. Using double quotes " " is necessary if
          you want to use shell variables within expression.

          gexpr supports the usual arithmetical operators  + - * / , the
          relational operators  < <= > >= == != , and all the standard C
          mathematical functions apart from frexp (3) and modf (3), which cannot
          be fully implemented since they actually return two values. In
          addition, gexpr provides the constants defined in math.h (M_PI, etc),
          the fact(n) function, which returns the factorial of n, and the rnd(n)
          function, which returns a random number between 0 and n.

          A nice feature of gexpr is the possibility of using other bases than
          10. For instance, this expression is allowed:

          $ gexpr "0x10 + 0b1010 + 010"
          34
          $ _

          the prefix "0x" denotes numbers written in base 16, "0b" numbers in
          base 2, and "0" octal numbers.

          The command "base nn" is used to display the results in a base between
          2 and 16. Example:

          gexpr> base 16
          output base is now 16
          gexpr> 256 * 2
          200
          gexpr> _

          The command "decimals nn" (or "dec nn") specifies the number of

                                        - 1 -     Formatted:  September 24, 2001

     GEXPR(1)                        GEXPR 2.0.2                        GEXPR(1)
                                      May 2001

          decimal positions. Example:

          gexpr> PI
          3.1415926525
          gexpr> dec 20
          decimal positions now 20
          gexpr> PI
          3.14159265258979311740
          gexpr> _

     COMMANDS
          base    specify the output base.

          dec(imals)
                  specify the number of decimals (default: 10).

          help    display a list of functions, constants, and commands.

          q(uit)  quit the program.

     OPTIONS
          --help, -h
                  display a short help.

          --base n, -b n
                  output results in base n.

          --no_prompt, -n
                  don't display the gexpr> prompt.

     EXAMPLES
          gexpr 2 + 10 / 2
          gexpr "sqrt(5) < log(10)"
          echo "sqrt(2)/2" | gexpr -n
          gexpr "sin($X) - tan($Y)"
          gexpr "$X + ($Y)*log10(${ZZ})"

          This is an interesting use of gexpr in a shell script:

          #!/bin/sh DEC=`echo "M_PI_2" | gexpr -n` EXA=`echo "M_PI_2" | gexpr -n
          -b16` echo "Pi/2 is $DEC (or $EXA in hexa)"

          Another example:

          #!/bin/sh
          X=0
          while [ `gexpr "$X < 10"` = 1 ]

                                        - 2 -     Formatted:  September 24, 2001

     GEXPR(1)                        GEXPR 2.0.2                        GEXPR(1)
                                      May 2001

          do
            X=`gexpr "$X + 0.2"`
            echo $X
          done

     BUGS
          It is awfully slow and its use cannot replace a "real" programming
          language supporting floating point math.

          Most errors are trapped but some are not, like overflows and
          underflows. For example, on the Linux box it was written on gexpr
          overflows when the result exceeds about 1.797e+308.

          It would be nice to add command-line editing. This would make gexpr
          quite bigger, though.

     AUTHOR
          Guido Gonzato <ggonza@tin.it>

     SEE ALSO
          expr (1), sh (1), bc (1)

                                        - 3 -     Formatted:  September 24, 2001