1 Jon Steinhart's (jon@fourwinds.com) External Program Hooks
2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 This blurb describes a changes to nmh that implement an interface
5 to external programs. This interface is different than the limited
6 interface provided by things like the rmmproc context entry.
12 I'm working on a project (grokmail) that will get released via GPL sometime
13 soon. This project keeps a database synchronized with the messages in the
14 mail system. New functionality is built on top of this database. This
15 functionality allows fast searching, and searching based on interest
16 criteria. The latter can be used for spam filtering.
18 The changes to nmh allow external programs to be run whenever a message is
19 added to a folder, removed from a folder, or refiled. The changes are
20 implemented in a general way so that it can be used for other purposes than
26 The changes add four new profile components:
28 add-hook: This is the full pathname of a program that is invoked
29 whenever a message is added to a folder. The program
30 is passed one argument which is the full pathname of the
31 message file. The program is executed after the message
32 is written so that it can act upon that message.
34 del-hook: This is the full pathname of a program that is invoked
35 whenever a message is deleted from a folder. The program
36 is passed one argument which is the full pathname of the
37 message file. The program is executed before the message
38 is written so that it can act upon that message.
40 ref-hook: This is the full pathname of a program that is invoked
41 whenever a message is refiled. The program is passed two
42 arguments: the first is the full pathname of the original
43 message file, the second is the full pathname of the final
44 message file. The program is executed after the message
47 message is moved from one place to another. So, for example, the command
51 The definition of refiling is a bit tricky. The refile hook is executed if a
52 causes the add hook to be executed, not the refile hook, because a new message
53 is created, the old one isn't moved.
55 These changes affect the following commands:
57 burst: The add hook is executed for messages burst from a digest, and
58 for the table of contents if -inplace is specified. The delete
59 hook is executed for the original message if -inplace is
60 specified. The refile hook is executed for messages that are
63 folder: The refile hook is executed for -pack.
65 inc: The add hook is executed when messages are incorporated.
67 refile: Either the add or refile hooks are executed.
69 rmf: The delete hook is executed when messages are deleted.
71 rmm: The delete hook is executed when messages are deleted.
73 sortm: The refile hook is executed for each message moved. Note that
74 a magic temporary message number of 2147483647 is used to hold
75 messages as they are being shuffled.
77 rcvstore: The add hook is executed when messages are stored.
79 mhstore: The add hook is executed when messages are stored.
81 Did I Do This Correctly?
82 ~~~~~~~~~~~~~~~~~~~~~~~~
84 Well, sort of. This all works, but I'm not really happy with it. The issue
85 is that an examination of the nmh code shows that message handling is scattered
86 all over the place. Although there are library routines such as folder_addmsg
87 and folder_delmsgs, they are not used consistently. Long term, I think that it
88 would be better to make all message handling go through the same choke points.
90 Also, I added a function to run the external programs. This sort of stuff is
91 also scattered around the nmh code, for example in the code to run the rmmproc.
92 Again, I'd like to make this more consistent in the long term.
94 What Files Did I Change?
95 ~~~~~~~~~~~~~~~~~~~~~~~~
107 ext_hook.c (new file)
112 In the original implementation availible config option, which are removed.
114 msg-hook: This is a text message that is output if the execution of
115 one of the external hook programs fails. There is a built-in
116 default message if none is specified.
117 This is removed, because I don't see this is necesarry and it's
118 not a good idee to pass a user provided string direkt in an