BASH: Keeping/replacing leading zeros with BC

Checksumfail · 07-20-2012, 02:43 PM

So I have made a script for copying a file with a name like IMG_2012_00754.tif and making incremental file names, so you can specify how many copies you want etc.

Now the problem is with file names like the above you get:

IMG_2012_00754.tif
IMG_2012_755.tif
IMG_2012_756.tif

For the purpose of this script keeping those leading zeros is important, and the script will be used on many different file name formats so the length of that last field is not a certain length (I can't force a field length of 5)

Is there anyway to stop BC from removing those leading zero's when I +1 to that field? Can I +1 with awk and keep them?

David the H. · 07-20-2012, 02:50 PM

We'd need to see your actual code to give you exact advice, but in general you can use printf to re-pad the numbers.

printf

Also see here for more on the built-in arithmetic, especially on how to handle zero-padded numbers. You shouldn't need to use any external tools for this.

arithmetic expressions

David the H. · 07-20-2012, 03:02 PM

Ok, here's one proof-of-concept solution for you.

Code:

file='IMG_2012_00754.tif'

#extract the last set of digits
oldnum=${file##*_}
oldnum=${oldnum%.*}

#increment number and pad it to the same width as the original
printf -v newnum "%0*d" "${#oldnum}" "$(( 10#$oldnum + 1 ))"

#build the new filename
echo "${file%_*}_${newnum}.tif"

#result from the above:
IMG_2012_00755.tif

Checksumfail · 07-20-2012, 03:29 PM

Thankyou so much, I've got it working now