Renaming Files Through Script

Question

I have a few files that are incorrectly named (with the extension added twice to the end). I was trying to write a bash script that would scan the directory and rename them, but it throws an error of:

cannot move '/var/random/file/file1.avi.mp4' to '{/var/random/file/file1.avi.mp4%.avi.mp4}.mp4': No such file or directory

I just want to properly rename the file extension, and am not sure where the error comes into play. For example, the error above, should have a file extension of .mp4. Below is my script, if someone could assist, I would be in debted...

#/bin/sh
for file in $(find /var/random/ -type f -name "*.avi.mp4"); do
  mv "$file" "{$file%.avi.mp4}.mp4"
done

Answer 1

You have a typo in your variable expansion:

"{$file%.avi.mp4}.mp4"

should have been:

"${file%.avi.mp4}.mp4"

However you might want to take a look at rename ( perl-rename )

perl-rename 's/[^.]+\.(?=[^.]+$)//' /var/random/*/*.avi.mp4

The regex will remove the second to last extension in file names:

/path/to/file/foo.bar.baz -> /path/to/file/foo.baz

Answer 2

find . -type f -name "*.avi.mp4" -print0 | while read -rd '' filename
do
if [ -e "${filename%.avi.mp4}.mp4" ]
then
  mv --backup "${filename}" "${filename%.avi.mp4}.mp4"
  #doing the backup only if the destination file exists to save space.
else
  mv "${filename}" "${filename%.avi.mp4}.mp4"
fi
done

What happened here :

1. We find out all the files ending with .avi.mp4 extension.
2. Since the file can contain newline characters, we make the filenames null terminated using print0 option of the find .
3. This output is piped into while loop where we are ready to parse the files.
4. Setting the delimiter -d option of the read to null( '' ) command we parse each of the null terminated filenames.
5. Finally we use parameter expansion/substitution to get rid of the .avi.mp4 at end of each file and append a .mp4 to each file at the mv phase. See reference 1.

References :

1. Shell parameter expansion
2. Move manual
3. Why use while instead of for?