Puppy Linux Discussion Forum

[Rattlehead]

I am trying to program a sort of "virtual corkboard" in console. It simply shows a grid with tags, whose colors vary according to their state, and each of them with an associated metadata file with notes, etc. The number of colums of the display can be modified on demand, and you can also insert blank slots on demand.

This is more or less where am I now. My main problem now is how to swap two tags. For example, tag 7 and tag 12 by typing 7x12, and the like.

I tried to store the information in the simplest way: a text file, and in each line either a tag, or only a newline to indicate a blank space in the corkboard.

I thought that swapping two lines inside a file would be a routine task, and that I was going to find in a second the one-liner to do it. To my surprise, there is very little information in Internet, only this linkhttp://www.unix.com/shell-programming-scripting/85230-swapping-switching-2-lines-using-sed.html, with a complicated awk script that I cannot get to work right. Seemingly, it is something nobody does.

Maybe my script has accumulated other errors along the way, but the absence of information on the issue makes me think that maybe:

a) Bash is not designed for the dynamic modification of files (I find it hard to believe, but the fact is I've googled for hours and found nothing)

b) Simple as it seems, the one-item-per-line format is counter-intuitive for bash, and I should have stored the info in a different way to access it (a huge single line with columns? Some kind of array? Using ampersands instead of newlines?)

Am I wasting my time? I did not think that it was going to be so difficult. Please give me some advice on what to do next...

[ken geometrics]

[Rattlehead]

Great! Thank you very much Ken, your answer opens some light after many hours of of darkness.

So, correct me if I got you wrong, the best working scheme would be:

1) when opening the program, loop through the data file to transfer it to an array

2) make all the modifications in the array (I should modify the display part so it reads the data from it)

3) when it's closing time, dump the modified array into the file to store data


Thank you very much

[technosaurus]

I never really understood how bash arrays worked, so I followed Barry's example of using "|" (same as the pipe symbol) for the separator and then using cut -d "|" -f $COLUMNNUMBER

[ken geometrics]

[Rattlehead]

Thank you guys both for the great resources. I am not a system administrator, just a guy who has rediscovered computing thanks to Linux and wants to get some simple bleep blops from his computer as a hobby, and this stuff really helps me.

Technosaurus, thank you for the cut oneliner too, it looks like a very "tight" way to define configurations.

Ken, I have some doubts about the solution you propose: