You might not believe that these are real programs but they are. You can find the binaries using `whereis`. For example on my linux install true is /bin/true.

The command line is pretty awesome.

http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob_p...

/bin/true source is a bit longer than expected but /bin/false implementation is really interesting : http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob_p...

Yeah, but try telling your boss that :)

    $ touch foo
    $ chmod +x foo
    $ ./foo
    $ echo $?
    0

    $ touch empty
    $ chmod +x empty
    $ time ./empty

    real    0m0.002s
    user    0m0.000s
    sys     0m0.000s

    $ echo "int main(){return 0;}" > trivial.c
    $ gcc trivial.c -o trivial
    $ time ./trivial

    real    0m0.001s
    user    0m0.000s
    sys     0m0.000s

(If I use my default zsh shell to execute ./empty, it gives me

    zsh: exec format error: ./empty
    ./empty  0.00s user 0.00s system 0% cpu 0.008 total

This is the normal pattern, just in case you forget to put "#!/bin/bash" at the top of the script, so that the script can be run anyway. This is also a source of confusion for some sysadmins, when a script works from the command line but not from something like a cron script.

Comparing to all this, a move instruction in userland won't really make a difference.

Edit: List on system calls required to execute trivial.c (on my Linux):

execve, brk, access, mmap, access, open, open, open, open, open, stat, open, stat, open, stat, open, stat, open, fstat, mmap, close, access, open, read, fstat, mmap, mprotect, mmap, mmap, close, mmap, mmap, mmap, arch_prctl, mprotect, mprotect, munmap, exit_group

    $ touch empty

    $ chmod +x empty 

    $ time ./empty 

        real    0m0.005s
        user    0m0.001s
        sys     0m0.001s

    $ echo "int main(){return 0;}" > trivial.c

    $ gcc trivial.c -o trivial

    $ time ./trivial

        real    0m0.002s
        user    0m0.001s
        sys     0m0.002s