Advanced Bash tutorial

[dougsweetser at gmail.com (Doug)]

Hello:

As we know, Jerry spoke the truth here:

>Unix commands were designed to be a toolbox. A number of simple
>command, each taking input from stdin and sending output to stdout. It
>is this simplicity and the pipe concept that makes Unix/Linux so
>powerful.
>--
>Jerry Feldman <gaf at blu.org>

My hobby is a rather obtuse kind of mathematics known as quaternions.
These are numbers with 4 parts, one for time three for space.  It
looked like a natural thing was to make animations using quaternions:
watch the ball go from here at this time to there a while later.

At the beginning of a software project, there are so many basic
choices to make.  My first was the project name: "command line
quaternions".  Each function would need to take an arbitrary number of
quaternions as input from STDIN or as arguments, then do its thing,
and crank the quaternions to STDOUT.  It is cool to make a river of
quaternions flow through functions.

As with any choice, there are limitations.  If I created an animation,
I wanted to record in the animation file how it was generated, all the
details of the command, so that months later, there would be a local
record of what was done to make the image.  Some people at
perlmonks.org recommended my Perl script should use an option,
-command "do_whatever | then_whatever", and include that into the
comment for the png and gif files that are generated.  Since graphing
is the end of the pipeline, I thought it was OK to break the model as
a way of record keeping.

If you want to see some of the images, they are available as
quaternions.sf.net.  Simple things are fun to look at and think about,
like the difference visually between space reflection and time
reflection.

doug

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