I've got bunch of files with ill-formed numbering:
prefix-#.ext | for files with number 1-9 prefix-##.ext | for files with number 10-99 prefix-###.ext | for files with number 100-999 Due to further processing I need all of their names to be in format: prefix-###.ext. Is there any easy way to do that?
On Debian, Ubuntu and derivatives, you can use the rename Perl script:
rename 's/(?<=-)([0-9]+)/sprintf "%03d", $1/e' prefix-*.ext Some systems may have this command installed as prename or perl-rename. Note that this is not the rename utility from the util-linux suite which does not provide an easy way to do this.
In zsh, you can use zmv to rename and the l parameter expansion flag to pad with zeroes.
autoload -U zmv zmv '(prefix-)(*)(.ext)' '$1${(l:3::0:)2}$3' You can also do this with a plain shell loop. Shells don't have nice string manipulation constructs; one way to pad with zeroes is to add 1000 and strip off the leading 1.
for x in prefix-*.ext; do n=${x%.ext}; n=${x##*-}; n=$((n+1000)) mv "$x" "${x%-*.ext}${n#1}${x##*-}" done Another way is to call the printf utility.
for x in prefix-*.ext; do n=${x%.ext}; n=${x##*-} mv "$x" "${x%-*.ext}$(printf %03d "$n")${x##*-}" done 
perl-rename, not just rename or prename. Perhaps something like this (untested)
for n in *.ext; do echo mv "$n" \ "prefix-$(printf %03d "$(basename ${n#prefix-} .ext)").ext" done Remove the echo to do the actual renaming.
Note: you have to be in the directory where the files are for this method to work; dealing with pathnames that contain a directory part is more complicated.
perl-rename, but I don't know how to make ### numbers from variable length numbers. for file in prefix-*.ext do num=`echo $file | sed 's/prefix-\(.*\).ext/\1/'` [ $num -lt 100 ] && mv $file prefix-`printf "%03d" ${num}`.ext done 