How to bulk-rename files with invalid encoding or bulk-replace invalid encoded characters?

You're going to run in some problems if you want to rename files and directories at the same time. Renaming just a file is easy enough. But you want to make sure the directories are also renamed. You can't simply mv Motörhead/Encöding Motorhead/Encoding since Motorhead won't exist at the time of the call.

So, we need a depth-first traversal of all files and folders, and then rename the current file or folder only. The following works with GNU find and Bash 4.2.42 on my OS X.

#!/usr/bin/env bash
find "$1" -depth -print0 | while IFS= read -r -d '' file; do
  d="$( dirname "$file" )"
  f="$( basename "$file" )"
  new="${f//[^a-zA-Z0-9\/\._\-]/}"
  if [ "$f" != "$new" ]      # if equal, name is already clean, so leave alone
  then
    if [ -e "$d/$new" ]
    then
      echo "Notice: \"$new\" and \"$f\" both exist in "$d":"
      ls -ld "$d/$new" "$d/$f"
    else
      echo mv "$file" "$d/$new"      # remove "echo" to actually rename things
    fi
  fi
done

You may change the regex by using new="${f//[\\\/\:\*\?\"<>|]/}" if you want to replace anything that Windows cannot handle.

Save this script as rename.sh, make it executable with chmod +x rename.sh. Then, call it like rename.sh /some/path.

Make sure to resolve any file name collisions (“Notice” announcements).

If you're absolutely sure it does the right replacements, remove the echo from the script to actually rename things instead of just printing what it does.

To be safe, I'd recommend testing this on a small subset of files first.

Options explained

To explain what goes on here:

• -depth will ensure directories are recursed depth-first, so we can "roll up" everything from the end. Usually, find traverses differently (but not breadth-first).
• -print0 ensures the find output is null-delimited, so we can read it with read -d '' into the file variable. Doing so helps us deal with all kinds of weird file names, including ones with spaces, and even newlines.
• We'll get the directory of the file with dirname. Don't forget to always quote your variables properly, otherwise any path with spaces or globbing characters would break this script.
• We'll get the actual filename (or directory name) with basename.
• Then, we remove any invalid character from $f using Bash's string replacement capabilities. Invalid means anything that's not a lower- or uppercase letter, a digit, a slash (\/), a dot (\.), an underscore, or a minus-hyphen.
• If $f is already clean (the cleaned name is identical to the current name), skip it.
• If $new already exists in directory $d (e.g., you have files named resume and résumé in the same directory), issue a warning. You don't want to rename it, because, on some systems, mv foo foo causes a problem.  Otherwise,
• We finally rename the original file (or directory) to its new name

Since this will only act on the deepest hierarchy, renaming Motörhead/Encöding to Motorhead/Encoding is done in two steps:

1. mv Motörhead/Encöding Motörhead/Encoding
2. mv Motörhead Motorhead

This ensures all replacements are done in the correct order.

Example files and test run

Let's assume some files in a base folder called test:

test
test/Motörhead
test/Motörhead/anöther_file.mp3
test/Motörhead/Encöding
test/Randöm
test/Täst
test/Täst/Töst
test/with space
test/with-hyphen.txt
test/work
test/work/resume
test/work/résumé
test/work/schedule

Here is the output from a run in debug mode (with the echo in front of the mv), i.e., the commands that would be called, and the collision warnings:

mv test/Motörhead/anöther_file.mp3 test/Motörhead/another_file.mp3
mv test/Motörhead/Encöding test/Motörhead/Encoding
mv test/Motörhead test/Motorhead
mv test/Randöm test/Random
mv test/Täst/Töst test/Täst/Tost
mv test/Täst test/Tast
mv test/with space test/withspace
Notice: "resume" and "résumé" both exist in test/work:
-rw-r—r--  …  …  test/work/resume
-rw-r—r--  …  …  test/work/résumé

Notice the absence of messages for with-hyphen.txt, schedule, and test itself.

I know that it's not exactly what you wanted, but if you know the original encoding, perhaps you can use convmv to change the encoding to UTF-8, which should fix most problems.

This worked for me on a folder with some invalid-encoded Polish filenames:

convmv -f cp1250 -t utf8 -r .

Note that this command doesn't actually rename anything; add --notest option to really rename the files.