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Yes, such packer/cruncher programs exists for various computers.
But you can easily 'fake' a packer in UNIX by creating this shell script:

        #!/bin/ksh

        FILE=/tmp/packer.${RANDOM}
        while [ -x $FILE ]
        do
                FILE=/tmp/packer.${RANDOM}
        done
        /bin/tail -n +2 $1 | /usr/bin/zcat >$FILE
        chmod u+x $FILE

        shift
        $FILE "$@"

        /bin/rm -f $FILE

and adding the line:

        #!<path-of-above-shell-script>

as the top line of your compressed binary file.  You may now execute your
compressed file.


Both shell-scripts and compress(1) are pretty standard in our UNIX world,
so you shouldn't run into any problems.  Of course, you can't use this
method across systems which aren't binary compatible.

Why bother writing a 'real' packer when this approach is so much simpler?
(though not much used, I must admit)  Writing small shell scripts which
'pack' and 'unpack' a file should be trivial.

It is posible to include the packer script itself into the 'packed'
executable, such as in 'self-extracting ZIP files.

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Encrypted packers

It should also be rather simple to generate encrypted executables
that need some hidden key to be able to look at the contents of the
executable.  Of course a determined person could decrypt the program
but they will need that key.

Of course it would make the program harder to find as you can no longer search
for scripts that use a particular program.

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