1. Compressed folders Support (OPTIONAL)
If Mutt was compiled with compressed folders support (by running the
configure script with the
--enable-compressed flag), Mutt can open folders
stored in an arbitrary format, provided that the user has a script to
convert from/to this format to one of the accepted.
The most common use is to open compressed archived folders e.g. with
gzip.
In addition, the user can provide a script that gets a folder in an
accepted format and appends its context to the folder in the
user-defined format, which may be faster than converting the entire
folder to the accepted format, appending to it and converting back to
the user-defined format.
There are three hooks defined (open-hook, close-hook and append-hook) which define commands to
uncompress and compress a folder and to append messages to an existing
compressed folder respectively.
For example:
open-hook \\.gz$ "gzip -cd %f > %t"
close-hook \\.gz$ "gzip -c %t > %f"
append-hook \\.gz$ "gzip -c %t >> %f"
You do not have to specify all of the commands. If you omit append-hook, the folder will be open and
closed again each time you will add to it. If you omit close-hook (or give empty command) , the
folder will be open in the mode. If you specify append-hook though you'll be able to
append to the folder.
Note that Mutt will only try to use hooks if the file is not in one of
the accepted formats. In particular, if the file is empty, mutt
supposes it is not compressed. This is important because it allows the
use of programs that do not have well defined extensions. Just use
"." as a regexp. But this may be surprising if your
compressing script produces empty files. In this situation, unset
$save_empty, so that
the compressed file will be removed if you delete all of the messages.
1.1. Open a compressed mailbox for reading
Usage: open-hook regexp "command"
The command is the command that can be used for
opening the folders whose names match regexp.
The command string is the printf-like format
string, and it should accept two parameters: %f, which is
replaced with the (compressed) folder name, and %t which is
replaced with the name of the temporary folder to which to write.
%f and %t can be repeated any number of times in the
command string, and all of the entries are replaced with the
appropriate folder name. In addition, %% is replaced by
%, as in printf, and any other %anything is left as is.
The command should not remove the original compressed file. The
command should return non-zero exit status if it
fails, so mutt knows something's wrong.
Example:
open-hook \\.gz$ "gzip -cd %f > %t"
If the command is empty, this operation is
disabled for this file type.
1.2. Write a compressed mailbox
Usage: close-hook regexp "command"
This is used to close the folder that was open with the open-hook command after some changes were
made to it.
The command string is the command that can be
used for closing the folders whose names match
regexp. It has the same format as in the open-hook command. Temporary folder in this
case is the folder previously produced by the open-hook command.
The command should not remove the decompressed file. The
command should return non-zero exit status if it
fails, so mutt knows something's wrong.
Example:
close-hook \\.gz$ "gzip -c %t > %f"
If the command is empty, this operation is
disabled for this file type, and the file can only be open in the
read-only mode.
close-hook is not called when you
exit from the folder if the folder was not changed.
1.3. Append a message to a compressed mailbox
Usage: append-hook regexp "command"
This command is used for saving to an existing compressed folder. The
command is the command that can be used for
appending to the folders whose names match
regexp. It has the same format as in the open-hook command. The temporary folder in
this case contains the messages that are being appended.
The command should not remove the decompressed file. The
command should return non-zero exit status if it
fails, so mutt knows something's wrong.
Example:
append-hook \\.gz$ "gzip -c %t >> %f"
When append-hook is used, the folder
is not opened, which saves time, but this means that we can not find
out what the folder type is. Thus the default ($mbox_type) type is always
supposed (i.e. this is the format used for the temporary folder).
If the file does not exist when you save to it, close-hook is called, and not append-hook. append-hook is only for appending to
existing folders.
If the command is empty, this operation is
disabled for this file type. In this case, the folder will be open and
closed again (using open-hook and
close-hook respectively) each time you
will add to it.
The compressed folders support can also be used to handle encrypted
folders. If you want to encrypt a folder with PGP, you may want to use
the following hooks:
open-hook \\.pgp$ "pgp -f < %f > %t"
close-hook \\.pgp$ "pgp -fe YourPgpUserIdOrKeyId < %t > %f"
Please note, that PGP does not support appending to an encrypted
folder, so there is no append-hook defined.
If you are using GnuPG instead of PGP, you may use the following hooks
instead:
open-hook \\.gpg$ "gpg --decrypt < %f > %t"
close-hook \\.gpg$ "gpg --encrypt --recipient YourGpgUserIdOrKeyId < %t > %f"
Note: the folder is temporary stored
decrypted in the /tmp directory, where it can be read by your system
administrator. So think about the security aspects of this.