Renaming files from bash in linux

Question

There is a bunch of files of the following format hh-mm-ss.png where hh, mm, ss are hour, minute and second. How can I rename all these files in the directory in a sequential way from 1.png til n.png so that all files sorted by hour, then by minutes, then by seconds. For example,

12-56-11.png -> 3.png
11-13-49.png -> 1.png
12-55-55.png -> 2.png

Answer 1

Here is a solution using a for loop and bash arithmetic:

i=1
for file in ??-??-??.png ; do
    mv "$file" $i.png
    let i++
done