Linux - Bash Script - Create index with leading zeros * Efficiently *

Hi All,

I am trying to write a bash script, and I am stuck trying to work out how to give an index leading zeros without slowing everything down too much.

In my script I have an index ($I) which is incrementing, and I am naming backup files with it thus:

zip "Backup-$I.zip" Path/To/Files

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At the risk of being pedantic (never!), my problem is that I would like to always have the filenames use three digits, it just looks kind of, well, untidy otherwise:

001
002
...
099
100
101

I figured I would add another variable to take the current value of $I, convert it to "000" format, and then use that variable to name the zip file something like this:

Padded=$(printf "%03d" $I)

zip "Backup-$Padded.zip" Path/To/Files/

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However, this seems to slow things to a crawl.  I'm not sure why, but I am guessing that it is creating a new shell instance each time it goes through or something?

Is there a better / more efficient option?

Thanks,

Alan.