The Compressed Folder feature allows NeoMutt to read mailbox files that are compressed. But it isn't limited to compressed files. It works well with encrypted files, too. In fact, if you can create a program/script to convert to and from your format, then NeoMutt can read it.
The feature adds three hooks to NeoMutt:
open-hook,
close-hook and
append-hook. They define commands to: uncompress a file; compress a file; append messages to an already compressed file.
There are some examples of both compressed and encrypted files, later. For now, the documentation will just concentrate on compressed files.
open-hook
regex
"shell-command"
close-hook
regex
"shell-command"
append-hook
regex
"shell-command"
The shell-command must contain two placeholders for filenames:
%f and
%t. These represent
“from” and
“to” filenames. These placeholders should be placed inside single-quotes to prevent unintended shell expansions.
If you need the exact string “%f” or “%t” in your command, simply double up the “%” character, e.g. “%%f” or “%%t”.
Table 11.1. Not all Hooks are Required
| Open | Close | Append | Effect | Useful if |
|---|---|---|---|---|
| Open | — | — | Folder is readonly | The folder is just a backup |
| Open | Close | — | Folder is read/write, but the entire folder must be written if anything is changed | Your compression format doesn't support appending |
| Open | Close | Append | Folder is read/write and emails can be efficiently added to the end | Your compression format supports appending |
| Open | — | Append | Folder is readonly, but can be appended to | You want to store emails, but never change them |
The command:
should return a non-zero exit status on failure
should not delete any files
open-hook regex "shell-command"
If NeoMutt is unable to open a file, it then looks for
open-hook that matches the filename.
If your compression program doesn't have a well-defined extension, then you can use
. as the regex.
Example 11.1. Example of
open-hook
open-hook '\.gz$' "gzip --stdout --decompress '%f' > '%t'"
NeoMutt finds a file, “example.gz”, that it can't read
NeoMutt has an
open-hook whose regex matches the filename:
\.gz$
NeoMutt uses the command
gzip -cd to create a temporary file that it
can
read
close-hook regex "shell-command"
When NeoMutt has finished with a compressed mail folder, it will look for a matching
close-hook to recompress the file. This hook is
optional.
If the folder has not been modified, the
close-hook will not be called.
Example 11.2. Example of
close-hook
close-hook '\.gz$' "gzip --stdout '%t' > '%f'"
NeoMutt has finished with a folder,
“example.gz”, that it opened with
open-hook
The folder has been modified
NeoMutt has a
close-hook whose regex matches the filename:
\.gz$
NeoMutt uses the command
gzip -c to create a new compressed file
The
close-hook can also include extra options, e.g. compression level:
--best
append-hook regex "shell-command"
When NeoMutt wants to append an email to a compressed mail folder, it will look for a matching
append-hook. This hook is
optional.
Using the
append-hook will save time, but NeoMutt won't be able to determine the type of the mail folder inside the compressed file.
NeoMutt will
assume
the type to be that of the
$mbox_type variable. NeoMutt also uses this type for temporary files.
NeoMutt will only use the
append-hook for existing files. The
close-hook will be used for empty, or missing files.
If your command writes to stdout, it is vital that you use
>> in the
“append-hook”. If not, data will be lost.
Example 11.3. Example of
append-hook
append-hook '\.gz$' "gzip --stdout '%t' >> '%f'"
NeoMutt wants to append an email to a folder,
“example.gz”, that it opened with
open-hook
NeoMutt has an
append-hook whose regex matches the filename:
\.gz$
NeoMutt knows the mailbox type from the
$mbox variable
NeoMutt uses the command
gzip -c to append to an existing compressed file
The
append-hook can also include extra options, e.g. compression level:
--best
NeoMutt assumes that an empty file is not compressed. In this situation, unset $save_empty, so that the compressed file will be removed if you delete all of the messages.
Encrypted files are decrypted into temporary files which are stored in the $tmp_dir directory. This could be a security risk.
# Example NeoMutt config file for the compress feature. # This feature adds three hooks to NeoMutt which allow it to # work with compressed, or encrypted, mailboxes. # The hooks are of the form: # open-hook regex "shell-command" # close-hook regex "shell-command" # append-hook regex "shell-command" # The 'append-hook' is optional. # Handler for gzip compressed mailboxes open-hook '\.gz$' "gzip --stdout --decompress '%f' > '%t'" close-hook '\.gz$' "gzip --stdout '%t' > '%f'" append-hook '\.gz$' "gzip --stdout '%t' >> '%f'" # Handler for bzip2 compressed mailboxes open-hook '\.bz2$' "bzip2 --stdout --decompress '%f' > '%t'" close-hook '\.bz2$' "bzip2 --stdout '%t' > '%f'" append-hook '\.bz2$' "bzip2 --stdout '%t' >> '%f'" # Handler for xz compressed mailboxes open-hook '\.xz$' "xz --stdout --decompress '%f' > '%t'" close-hook '\.xz$' "xz --stdout '%t' > '%f'" append-hook '\.xz$' "xz --stdout '%t' >> '%f'" # Handler for pgp encrypted mailboxes # PGP does not support appending to an encrypted file open-hook '\.pgp$' "pgp -f < '%f' > '%t'" close-hook '\.pgp$' "pgp -fe YourPgpUserIdOrKeyId < '%t' > '%f'" # Handler for gpg encrypted mailboxes # gpg does not support appending to an encrypted file open-hook '\.gpg$' "gpg --decrypt < '%f' > '%t'" close-hook '\.gpg$' "gpg --encrypt --recipient YourGpgUserIdOrKeyId < '%t' > '%f'" # vim: syntax=neomuttrc
