How to zero pad numbers in file names in Bash?

It's not pure bash, but much easier with the Perl version of rename:

rename 's/\d+/sprintf("%05d",$&)/e' foo*

Where 's/\d+/sprintf("%05d",$&)/e' is the Perl replace regular expression.

• \d+ will match the first set of numbers (at least one number)
• sprintf("%05d",$&) will pass the matched numbers to Perl's sprintf, and %05d will pad to five digits

In case N is not a priori fixed:

for f in foo[0-9]*; do  mv "$f" "$(printf 'foo%05d' "${f#foo}")"done

I had a more complex case where the file names had a postfix as well as a prefix. I also needed to perform a subtraction on the number from the filename.

For example, I wanted foo56.png to become foo00000055.png.

I hope this helps if you're doing something more complex.

#!/bin/bashprefix="foo"postfix=".png"targetDir="../newframes"paddingLength=8for file in ${prefix}[0-9]*${postfix}; do  # strip the prefix off the file name  postfile=${file#$prefix}  # strip the postfix off the file name  number=${postfile%$postfix}  # subtract 1 from the resulting number  i=$((number-1))  # copy to a new name with padded zeros in a new folder  cp ${file} "$targetDir"/$(printf $prefix%0${paddingLength}d$postfix $i)done