zero padding of file names

I want to do zero-padding for names of files. what should I do if not all images exist like 1.JPEG doesn't exist or 99.JPEG or 110.JPEG ?

 $ for n in $(seq 9); do mv $n.JPEG 0$n.JPEG; done; mv: cannot stat ‘1.JPEG’: No such file or directory

I do not want to rename manually because order of videos are important.

2 Answers

You can use if inside the loop to check if the file exists. And if it does, then only mv operation would take place.

for n in $(seq 9)
do if [[ -f $n.JPEG ]] then mv $n.JPEG 0$n.JPEG fi
done;

Or in one line:

for n in $(seq 9); do if [[ -f $n.JPEG ]]; then mv $n.JPEG 0$n.JPEG; fi done;

Using parameter expansion you can split the filename into name and extension, then glue them together with printf formatting

#!/bin/bash
for i in *; do mv $i $(printf %04d.%s\\n ${i/./ })
done

printf formatting:

${parameter/pattern/string}

Pattern substitution; parameter is expanded and the longest match of pattern against its value is replaced with string.