Basic Usage (Perl rename)

If you have Perl’s rename (aka prename) installed, replace any character that isn’t alphanumeric, a dot, or a hyphen with an underscore:

rename -- 's/[^0-9a-zA-Z.-]/_/g' *

The -- prevents filenames starting with - from being interpreted as flags.

Note: On many distros (e.g. Rocky Linux, Fedora), the default rename is from util-linux and does not support Perl regex. Check with rename --version. If you see util-linux, use the for loop approach below instead, or install prename.

For Loop Approach (No Perl rename Required)

This works on any system with perl installed, regardless of which rename you have:

for f in /path/to/files/*; do
  dir=$(dirname "$f")
  base=$(basename "$f")
  newname=$(echo "$base" | perl -CSD -pe 's/[^0-9a-zA-Z.-]/_/g')
  [ "$base" != "$newname" ] && mv "$dir/$base" "$dir/$newname"
done

Preserving Japanese Characters

To keep kanji, hiragana, katakana, and common Japanese punctuation intact:

for f in /path/to/files/*; do
  dir=$(dirname "$f")
  base=$(basename "$f")
  newname=$(echo "$base" | perl -CSD -pe 's/[^0-9a-zA-Z.\p{Han}\p{Hiragana}\p{Katakana}ー々〜～・「」-]/_/g')
  [ "$base" != "$newname" ] && mv "$dir/$base" "$dir/$newname"
done
  • -CSD — tells Perl to handle UTF-8 on stdin, stdout, and default layers
  • \p{Han} — kanji (漢字)
  • \p{Hiragana} — hiragana (ひらがな)
  • \p{Katakana} — katakana (カタカナ)
  • ー々〜～・「」 — common Japanese punctuation (long vowel mark, repeat kanji mark, wave dash, middle dot, brackets)

With Perl’s rename the equivalent command is:

rename -- 's/[^0-9a-zA-Z.\p{Han}\p{Hiragana}\p{Katakana}ー々〜～・「」-]/_/g' *

Updated: