Shell Programming and Scripting

A few things to be aware:
Using a for loop here limits to files that do not have spaces, if any file matched by find contains spaces the script would introduce a behavior you do not want. And by the way, find will process any directory tree recursively.

find . -name "folder.jpg" will not be limited to only files but to directories that contains that name as well.

Here's another untested version that might process any files named folder.jpeg or folder.jpg in any directory starting in the current one.
If you like what echo produces, comment it and uncomment the convert.
As an example it does change the name with one of your new names suggestions.

Code:

#!/bin/bash

find . -type f -name "folder.jp*g" | while read f
do
  path="${f%/*}"
  extension="${f##*.}"
  echo "$f -> ${path}/album_art_small.${extension}"
  # convert "$f" -resize 200x200\!  "${path}"/album_art_small."${extension}"
done

Thank you! That solved one problem. I tested it, and it will actually work a couple directories down, too. Only it won't if there are any spaces in the directory name. Is there any way to fix this?

If the above script is working for you except for the set of filenames to be processed and the output names your want, let's try the following:

Code:

#!/bin/bash
find . -name '[Ff]older.jpg' -o -name '[Ff]older.jpeg' |
while read -r f
do
	convert -resize 200x200\! "$f" "${f%/*}/thumb-${f##*/}"
done

The find command in this script will identify files named Folder.jpg, folder.jpg, Folder.jpeg, and folder.jpeg anywhere in the file hierarchy rooted in the current directory. If you want to add more filenames to the list of those to be processed, add an additional -o 'pattern' for each additional filename matching pattern desired to the end of the find command. For each of the files found, this script it will create a file in the directory where that file was found with the prefix thumb- added to the final component of the pathname.

Using find ... | while read ... f instead of for f in `find ...` allows the find command to run in parallel with the thumbnail creations (instead of creating a complete list of files to process before starting to create the thumbnails) and requires less memory in the shell to get the job done. The quotes added to the $f parameter expansions protect against the possibility of your directory names containing any spaces, tabs, or pathname expansion characters. The ${f%/*} parameter expansion extracts the pathname of the directory in which the file resides and the ${f##*/} parameter expansion extract the final component of the pathname. Using those two expansions allows us to insert the thumb- filename prefix in the correct spot in the output file pathname. If you just want to use the filename album_art_small.jpg as your output filename, the convert command in the above script can be changed to:

Code:

	convert -resize 200x200\! "$f" "${f%/*}/album_art_small.jpg"

but note that if you do that and you happen to have two or more files to be processed in a single directory, the last one processed will be the only thumbnail that is kept (thumbnails processed earlier will be overwritten by thumbnails processed later).