I don't have a tune for this so it might be more of a poem than a song.

    SEVEN RINGS OF SHELL

    Let your level of shell
    be denoted by L,
    with a range greater than
    or equal to the number of zero.

    You put a backslash
    at the command-line of bash.
    Escaped. We are safe. Say "yay!"
    This is glory, oh glory.

    Cry loudly my friend --
    then error amend;
    defenses eaten, look into man.
    Trembling are all but the hero.

    It's a power of two,
    here's what to do:
    Exponent L is the way.
    No worry, no worry.

            --- vive-la-liberte, 2015

Any English teachers or similar in the audience may have a glass of wine on the house provided they keep quiet...

Just kidding. Feedback is welcome -- that's how we improve.