[kwlug disc.] bash script basics

[Chris Frey]

On Fri, Feb 09, 2007 at 07:19:32PM -0500, Richard Weait wrote:
> The data file might look like this.
> 
> #
> # this is a fake data file
> #
> 
> 1 2 3 # three whitespace separated numbers
> 4 5 6
> 7 8 9
> 10 11 12  # each number up to 5 or 6 digits
> # comments
> 13 14 15 # real data is arbitrary, not sequential
> 16 17 18


You can prefilter with grep, removing comments and blank lines.  Keeping
it simple:

	grep -v "^ *#" | grep -v "^$"

Then you can read each line with:

	while read A B C D ; do
		...
	done

This is a shell command, reading space separated input and putting them
in the given environment variables.  You want an extra D at the end
to catch any "comments".

Then do a few if statements to make sure A, B, and C are valid,
then run your command:

	command $A $B $C

This all assumes the data is coming in on stdin.

- Chris