sorting filenames numerically when they have non-numeric prefix

Question

I have files in the following format: x1 x2 ... x10 x11 ... x101 ...

I want to rename these files, so they all have the same name length: x001 x002 ... x010 ...

I can do this with files, that don't have the non-numeric prefix (just using sort -n followed by a while read x;), but sort doesn't recognize the numeric value, when it's not on the beginning of the file-name.

Answer 1

You can try sorting the files using the v (version) option of ls e.g. ls -1v. Or you can use numeric sort with x as the delimiter: ls | sort -n -t 'x' +1

But you don't have to sort the files to rename them. You can just look at the length of the file name and pad it with zeros if necessary. Here is a small script which does that:

prefix=x
maxLength=4

for file in ${prefix}*
do
 if [ ${#file} -lt $maxLength ]
 then
     newFile=$file
     while [ ${#newFile} -lt $maxLength ]
     do
       newFile=${newFile/$prefix/${prefix}0}
     done   
     mv $file $newFile
 fi
done

Answer 2

Are you sure you need to sort them first?

m=0
for f in x*; do
  [ "${#f}" -gt "$m" ] &&
    m=${#f}
done

for f in x*; do
  echo mv -- "$f" "${f%${f#?}}$( printf '%0.*d' $(( m - 1 )) "${f#?}" )"
done 

If your printf implementation doesn't support the syntax above, use printf "%0.$(( m - 1 ))d" "${f#?}".

Remove echo when satisfied.

Answer 3

You need rename, while there are similar tools, which could serve you too:

touch x1 x2 x10 x11 x101 
ls ; rename 's/x/x0/' x[0-9] 

x1 x10 x101 x11 x2

ls ; rename 's/x/x0/' x[0-9][0-9] 

x01 x02 x10 x101 x11

ls

x001 x002 x010 x011 x101

'rename' is part of some perl package, if you need to install it, at least available for Linux.

Without rename, there is a similar solution with a loop:

rm * 
touch x1 x2 x10 x11 x101
for f in  x[0-9] ; do mv $f ${f/x/x0}; done 
for f in  x[0-9][0-9] ; do mv $f ${f/x/x0}; done ; ls 

x001 x002 x010 x011 x101