Ubuntu Manpage: convmv - converts filenames from one encoding to another

NAME

       convmv - converts filenames from one encoding to another

SYNOPSIS

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

OPTIONS

-f ENCODING
specify the current encoding of the filename(s) from which should be converted

-t ENCODING
specify the encoding to which the filename(s) should be converted

-i interactive mode (ask y/n for each action)

-r recursively go through directories

--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.).

--qfrom , --qto
be more quiet about the "from" or "to" of a rename (if it screws up your terminal e.g.). This will in
fact do nothing else than replace any non-ASCII character (bytewise) with ? and any control character
with * on printout, this does not affect rename operation itself.

--exec command
execute the given command. You have to quote the command and #1 will be substituted by the old, #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

--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.

--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.

--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.

--notest
Needed to actually rename the files. By default convmv will just print what it wants to do.

--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 convmv make 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 file in a minimum of time.

--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. This sequences like %20
etc. are sometimes produced when downloading via http or ftp.

--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.

--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 mapchars mount option of mount.cifs on Linux).

ntfs-pretty(-undo) for 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.

--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.

--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
print a short summary of available options

--dump-options
print a list of all available options

DESCRIPTION

convmv is meant to help convert a single filename, a directory tree and the contained files or a whole
filesystem into a different encoding. It just converts the filenames, not the content of the files. A
special feature of convmv is that it also takes care of symlinks, also converts the symlink target
pointer in case the symlink target is being converted, too.

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.

BUGS

       no bugs or fleas known

DONATE

       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.

perl v5.40.1                                       2025-03-12                                          CONVMV(1)