David M Williams
Sunday, 28 December 2008 18:47
Opinion and Analysis
Page 2 of 3
To represent just how much we’re laughing – because, after all, we’re dashing over snow-capped fields in a sleigh which, in a gaping continuity flaw, is pulled by a horse and not twelve reindeer – we need a huge LOL!
Fear not! Linux comes equipped with a command called banner which will print a message in huge characters for printing on, well, banners, really.
Thus the command
% banner lol
gives output of
# #### #
# # # #
# # # #
# # # #
# # # #
###### #### ######
And if that’s not laughing out loud then I don’t know what is !
Now to unravel some mystery! The next thing that transpires on the magical snow ride is that bells on bobtails ring.
We can add some genuine music to our carol here; Linux offers a way of ringing the system bell. This actually harks back a long way to the early history of computing.
ASCII code number seven – which can be represented by CTRL-G – is known as the “BELL” (or “BEL”) code.
This code doesn’t print anything when sent to an output device but instead makes the terminal beep – or ring its bell.
Therefore
% echo ^G > BobTails
means we’re making bells on bobtails ring by sending a bell to a text file called BobTails.
^G represents CTRL-G but how you type it will differ; you can’t actually type the literal characters ^ and G, that won’t work. You need to either press CTRL and G together or, in some systems, press CTRL-V to indicate you are about to enter a special code, then press CTRL-G. That’s how it works in the vi text editor as well as the command lines of some shells.
This isn’t just some Linux oddity; it’s true of Windows too; if you try printing a program file to the screen (eg TYPE C:\Windows\Explorer.exe) you will get loads of gibberish and the occasional beep.
Every beep is because the file contained a byte with the value 7. When printing to the screen, this is interpreted as ASCII code 7 and the bell rings.
This is part of computing history; early terminals – line printers even – would beep to attract operator attention when a tape needing changing or other important things required aid.
University students have often found merriment in combining the bell with the write command which sends a message to somebody else’s terminal. Certain people would get carried away and use the wall command instead; this was never smart – wall (write all) would send your message to the terminal of every logged in user and was sure to attract sysadmin attention!
With that mystery over, let’s wrap up as well as hit the very jingly chorus!
CONTINUED
