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mddiff(1) Sync Mail Dir (smd) documentation mddiff(1)

NAME

mddiff - computes diff for maildirs

SYNOPSIS

mddiff [--max-mailno mno] [--db-file dbf] [-l|--list] [-s|--symlink]

[--exclude globexpr] [-v|--verbose] [-d|--dry-run]
[-n|--no-delete] [--no-move] [--help] [--sha1sum] paths

DESCRIPTION

mddiff computes the delta from an old status of a maildir (previously recorded in a support file, called db file) and the current status, generating a set of commands (a diff) that a third party software can apply to synchronize a (eventually remote) copy of the maildir.

If paths is a single file name, and that file is a fifo, mddiff reads from it file names separated by new line and outputs the sha1 of its header and body separated by space.


$ mddiff /tmp/fifo_for_mddiff
806a0ffe4f29766effd764... 463e543da9dac8e298...
582cbb6a5cd3ce13965c8c... 8fa60a7458b1157193...

...

If paths is a single file name, and that file is a fifo, and the -s option is passed, mddiff reads from that fifo two lines at a time, respectively a source name and a target name. It then creates a symlink named as as the target name pointing to the source name. If some dictories need to be created in order to create the symlink, this is also done. mddiff will print 'OK' on stdout to signal a success, 'ERROR' to signal an error.

If paths is a list of directories, mddiff outputs a list of actions a client has to perform to synchronize a copy of the same maildirs. This set of actions is relative to a previous status of the maildir stored in the db file. The input directories are traversed recursively, and every file encountered inside directories named cur/ and new/ is a potential mail message (if it contains no \n\n it is skipped).


$ mddiff ~/Mail/
ADD ~/Mail/cur/1239038050.14937_1.garfield:2,S 66532ebb05b252e...

...

Every client (endpoint using mddiff for synchronization) must use a different db-file, and the db-file is strictly related with the set of directories given as arguments, and should not be used with a different directory set. Adding items to the directory set is safe, while removing them may not do what you want (delete actions are generated).

mddiff does not alter the dbf file, it generates a new one called dbf.new. It is up to the higher level tool smd-server(1) to rename dbf.new to dbf in case the other endpoint successfully applied the diff.

The --exclude option tells mddiff to ignore all paths matching the given glob(7) expression. This option can be passed multiple times. Matching is performed using fnmatch(3) with no special flags, thus '*' and '?' match any character including '/'. Matching is performed when a directory is entered. If the match is successful, the directory and all its subedirectories are skipped.

The --no-delete option tells mddiff to not output a DELETE action for files that disappear. Note that a DELETE action is anyway generated for files that are moved (i.e. move is COPY plus DELETE). The result is that deletions are not propagated to the other endpoint.

OPTIONS

Estimation of max mail message number (defaults to the number of messages in the db-file + 1000 or 500000 if there is no db-file). You may want to decrease it for the first run on small systems. It is anyway increased automatically when needed
Name of the cache for the endpoint (default db.txt)
Exclude paths maching the given expression
Behaves like the sha1sum utility
Behaves like mkdir -p
Behaves like mkfifo
Only list the mailboxes recursively contained in paths
Create symlinks for paths read on the input fifo
Increase program verbosity (printed on stderr)
Do not generate a new db-file
Do not track deleted files
Do not generate MOVE (only COPY + DELETE)
This help screen

NOTES

mddiff is a low level utility, used by smd-server and smd-client. You should use higher level tools like smd-pull(1), smd-push(1) and smd-loop(1)

SEE ALSO

smd-client(1), smd-server(1), smd-pull(1), smd-push(1), smd-loop(1)

AUTHOR

Enrico Tassi <gares@fettunta.org>

21 April 2021