CONVMV(1)

📦
version 2.06 · 8 versions
, in debian trixie, ubuntu resolute, ubuntu stonking

💖 CONVMV — converts filenames from one encoding to another 💖

okay bestie, gather round, because convmv is the little Perl icon we did not know we needed. Its whole entire job? Converting filenames from one encoding to another. That's it. That's the gig. No cap. ✨

🌈 SYNOPSIS 🌈

convmv [options] FILE(S) ... DIRECTORY(S)

like, you hand it some files, you hand it some directories, you hand it options, and it goes to work. the way that it just… does it 💅

✨ OPTIONS ✨

🔤 The encoding basics

  • -f ENCODING — tell it the current encoding of the filename(s) — the "from" side of the glow-up. This is what you're converting away from, bestie.
  • -t ENCODING — tell it the encoding the filename(s) should be converted to. The "to" side. The destination. The after picture. 🦋

🕹️ How it behaves

  • -i — interactive mode: it asks you y/n for each action. Consent-first behavior, we love to see it 🫶
  • -r — recursively go through directories. It will keep going deeper. It will not stop. main character energy fr fr.
  • --nfc — target files will be normalization form C for UTF-8 (Linux etc.)
  • --nfd — target files will be normalization form D for UTF-8 (OS X etc.).

🙈 Quiet-ifying the printout

  • --qfrom, --qto — be more quiet about the "from" or the "to" of a rename (handy if it screws up your terminal, e.g.). Honestly this does nothing else than replace any non-ASCII character (bytewise) with ? and any control character with * on printout. It does not affect the rename operation itself. so like, cosmetic only, no cap.

🪄 Running your own command

  • --exec command — execute the given command. You have to quote the command, and #1 will be substituted by the old filename, #2 by the new filename. Using this option, link targets will stay untouched. Have in mind that #1 and #2 will be quoted by convmv already — you must not add extra quotation marks around them. 🙅♀️

Example:

convmv -f latin1 -t utf-8 -r --exec "echo #1 should be renamed to #2" path/to/files

📚 Listings and memory

  • --list — list all available encodings. To get support for more Chinese or Japanese encodings, install the Perl HanExtra or JIS2K Encode packages. Also, installing the Perl IMAPUTF7 package might be helpful if you need this encoding. slay, more encodings ✨
  • --lowmem — keep memory footprint low by not creating a hash of all files. This disables checking if symlink targets are in subtree. Symlink target pointers will be converted regardlessly. If you convert multiple hundredthousands or millions of files, the memory usage of convmv might grow quite high — this option would help you out in that case. 🫶

🧠 Smart mode and its discontents

  • --nosmart — by default convmv will detect if a filename is already UTF8 encoded and will skip this file if conversion from some charset to UTF8 should be performed. --nosmart will also force conversion to UTF-8 for such files, which might result in "double encoded UTF-8" (see section below). 💀
  • --fixdouble — using the --fixdouble option, convmv does only convert files which will still be UTF-8 encoded after conversion. That's useful for fixing double-encoded UTF-8 files. All files which are not UTF-8 or will not result in UTF-8 after conversion will not be touched. Also see chapter "How to undo double UTF-8 ..." below. 👑

⚠️ Actually doing the thing

  • --notest — needed to actually rename the files. By default, convmv will just print what it wants to do. So yeah, without this you're just ✨ manifesting ✨ the rename. It will not happen. Do not forget this one, I am begging you 😭

🤖 For the GUI girlies

  • --parsable — this is an advanced option that people who want to write a GUI front end will find useful (some others maybe, too). It will make convmv print out what it would do in an easy parsable way. The first column contains the action or some kind of information, the second column mostly contains the file that is to be modified, and if appropriate the third column contains the modified value. Each column is separated by \0\n (nullbyte newline). Each row (one action) is separated by \0\0\n (nullbyte nullbyte newline).
  • --run-parsable — this option can be used to blindly execute the output of a previous --parsable run. This way it's possible to rename a huge amount of files in a minimum of time. 🔥

🕰️ Timestamps, overwrites, escapes

  • --no-preserve-mtimes — modifying filenames usually causes the parent directory's mtime being updated. Since version 2, convmv by default resets the mtime to the old value. If your filesystem supports sub-second resolution, the sub-second part of the atime and mtime will be lost, as Perl does not yet support that. With this option you can disable the preservation of the mtimes.
  • --replace — if the file to which shall be renamed already exists, it will be overwritten if the other file content is equal. 👀
  • --unescape — this option will remove this ugly % hex sequences from filenames and turn them into (hopefully) nicer 8-bit characters. After --unescape you might want to do a charset conversion. These sequences like %20 etc. are sometimes produced when downloading via http or ftp.

🔠 Case-flipping

  • --upper, --lower — turn filenames into all upper or all lower case. When the file is not ASCII-encoded, convmv expects a charset to be entered via the -f switch.

🗺️ Custom mappings

  • --map=some-extra-mapping — apply some custom character mappings. Currently supported are:
    • ntfs-sfm(-undo), ntfs-sfu(-undo) for the mapping of illegal ntfs characters for Linux or Macintosh cifs clients (see MS KB 117258, also the mapchars mount option of mount.cifs on Linux).
    • ntfs-pretty(-undo) for the mapping of illegal ntfs characters to pretty legal Japanese versions of them.

See the map_get_newname() function how to easily add own mappings if needed. Let me know if you think convmv is missing some useful mapping here. 💌

🇹🇷 The dotless i situation

  • --dotlessi — care about the dotless i/I issue. A lowercase version of "I" will also be dotless, while an uppercase version of "i" will also be dotted. This is an issue for Turkish and Azeri.

By the way: the superscript dot of the letter i was added in the Middle Ages to distinguish the letter (in manuscripts) from adjacent vertical strokes in such letters as u, m, and n. J is a variant form of i which emerged at this time and subsequently became a separate letter. history lesson AND filename conversion, we contain multitudes 🎀

🔡 The sz ligature

  • --caseful-sz — let convmv convert the sz ligature (U+00DF) to the uppercase version (U+1E9E) and vice versa. As of 2017, most fs case mapping tables don't treat those two code points as case equivalents. Thus the default of convmv is to treat it caseless for now also (unless this option is used).

🆘 Help me

  • --help — print a short summary of available options.
  • --dump-options — print a list of all available options.

more coming bestie, don't go anywhere 💜

✨ DESCRIPTION ✨

okay bestie so convmv is literally the glow-up your filenames have been waiting for 💅 It helps you convert a single filename, a whole directory tree and the files inside it, or even an entire filesystem into a different encoding. And the way it does it? It only converts the filenames, not the content of the files. Not one byte of your actual file data gets touched, periodt. A special feature of convmv is that it also takes care of symlinks, and it also converts the symlink target pointer in case the symlink target is being converted, too. Obsessed.

All this comes in very handy when one wants to switch over from old 8-bit locales to UTF-8 locales. It is also possible to convert directories to UTF-8 which are already partly UTF-8 encoded. convmv is able to detect if certain files are UTF-8 encoded and will skip them by default. To turn this smartness off use the --nosmart switch.

🎀 Filesystem issues 🎀

Almost all POSIX filesystems do not care about how filenames are encoded, here are some exceptions:

HFS+ on OS X / Darwin

Linux and (most?) other Unix-like operating systems use the so called normalization form C (NFC) for its UTF-8 encoding by default but do not enforce this. HFS+ on the Macintosh OS enforces normalization form D (NFD), where a few characters are encoded in a different way. On OS X it's not possible to create NFC UTF-8 filenames because this is prevented at filesystem layer. On HFS+ filenames are internally stored in UTF-16 and when converted back to UTF-8 (because the Unix based OS can't deal with UTF-16 directly), NFD is created for whatever reason. See http://developer.apple.com/qa/qa2001/qa1173.html for defails. I think it was a very bad idea and breaks many things under OS X which expect a normal POSIX conforming system. Anywhere else convmv is able to convert files from NFC to NFD or vice versa which makes interoperability with such systems a lot easier.

APFS on macOS

Apple, with the introduction of APFS in macOS 10.3, gave up to impose NFD on user space. But once you enforced NFD there is no easy way back without breaking existing applications. So they had to make APFS normalization-insensitive, that means a file can be created in NFC or NFD in the filesystem and it can be accessed with both forms also. Under the hood they store hashes of the normalized form of the filename to provide normalization insensitivity. Sounds like a great idea? Let's see: If you readddir a directory, you will get back the files in the the normalization form that was used when those files were created. If you stat a file in NFC or in NFD form you will get back whatever normalization form you used in the stat call. So user space applications can't expect that a file that can be stat'ed and accessed successfully, is also part of directory listings because the returned normalization form is faked to match what the user asked for. Theoretically also user space will have to normalize strings all the time. This is the same problem as for the case insensitivity of filenames before, which still breaks many user space applications. Just that the latter one was much more obvious to spot and to implement than this thing. So long, and thanks for all the fish.

JFS

If people mount JFS partitions with iocharset=utf8, there is a similar problem, because JFS is designed to store filenames internally in UTF-16, too; that is because Linux' JFS is really JFS2, which was a rewrite of JFS for OS/2. JFS partitions should always be mounted with iocharset=iso8859-1, which is also the default with recent 2.6.6 kernels. If this is not done, JFS does not behave like a POSIX filesystem and it might happen that certain files cannot be created at all, for example filenames in ISO-8859-1 encoding. Only when interoperation with OS/2 is needed iocharset should be set according to your used locale charmap.

NFS4

Despite other POSIX filesystems RFC3530 (NFS 4) mandates UTF-8 but also says: "The nfs4_cs_prep profile does not specify a normalization form. A later revision of this specification may specify a particular normalization form." In other words, if you want to use NFS4 you might find the conversion and normalization features of convmv quite useful.

FAT/VFAT and NTFS

NTFS and VFAT (for long filenames) use UTF-16 internally to store filenames. You should not need to convert filenames if you mount one of those filesystems. Use appropriate mount options instead!

🌈 How to undo double UTF-8 (or other) encoded filenames 🌈

Sometimes it might happen that you "double-encoded" certain filenames, for example the file names already were UTF-8 encoded and you accidentally did another conversion from some charset to UTF-8. You can simply undo that by converting that the other way round. The from-charset has to be UTF-8 and the to-charset has to be the from-charset you previously accidentally used. If you use the --fixdouble option convmv will make sure that only files will be processed that will still be UTF-8 encoded after conversion and it will leave non-UTF-8 files untouched. You should check to get the correct results by doing the conversion without --notest before, also the --qfrom option might be helpful, because the double utf-8 file names might screw up your terminal if they are being printed - they often contain control sequences which do funny things with your terminal window. If you are not sure about the charset which was accidentally converted from, using --qfrom is a good way to fiddle out the required encoding without destroying the file names finally.

🍓 How to repair Samba files 🍓

When in the smb.conf (of Samba 2.x) there hasn't been set a correct "character set" variable, files which are created from Win* clients are being created in the client's codepage, e.g. cp850 for western european languages. As a result of that the files which contain non-ASCII characters are screwed up if you ls them on the Unix server. If you change the "character set" variable afterwards to iso8859-1, newly created files are okay, but the old files are still screwed up in the Windows encoding. In this case convmv can also be used to convert the old Samba-shared files from cp850 to iso8859-1.

By the way: Samba 3.x finally maps to UTF-8 filenames by default, so also when you migrate from Samba 2 to Samba 3 you might have to convert your file names.

🧚 Netatalk interoperability issues 🧚

When Netatalk is being switched to UTF-8 which is supported in version 2 then it is NOT sufficient to rename the file names. There needs to be done more. See http://netatalk.sourceforge.net/2.0/htmldocs/upgrade.html#volumes-and-filenames and the uniconv utility of Netatalk for details.

🕊️ Dovecot 🕊️

Some versions of Dovecot use UTF-8 for Maildir folders, some use IMAP-UTF-7 aka mUTF7 aka modified UTF-7. In certain migration scenarios, administrators might have to convert the folder names, which can be done with convmv. Make sure to install the Perl IMAPUTF7 package to make use of this encoding with convmv.

👀 SEE ALSO 👀

locale(1) utf-8(7) charsets(7)

🐛 BUGS 🐛

no bugs or fleas known

You can support convmv by doing a donation, see <https://www.j3e.de/donate.html>

👑 AUTHOR 👑

Bjoern JACKE

Send mail to bjoern [at] j3e.de for bug reports and suggestions.

and that's the whole vibe bestie 💅 This iconic page is from convmv's perl v5.40.1 era, dated 2025-03-12, and yes it's CONVMV(1) — go off, king 🫶✨

📦 where this page comes from