3 Jon Steinhart's (jon@fourwinds.com) External Program Hooks
4 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6 This blurb describes a changes to nmh that implement an interface
7 to external programs. This interface is different than the limited
8 interface provided by things like the rmmproc context entry.
14 I'm working on a project (grokmail) that will get released via GPL sometime
15 soon. This project keeps a database synchronized with the messages in the
16 mail system. New functionality is built on top of this database. This
17 functionality allows fast searching, and searching based on interest
18 criteria. The latter can be used for spam filtering.
20 The changes to nmh allow external programs to be run whenever a message is
21 added to a folder, removed from a folder, or refiled. The changes are
22 implemented in a general way so that it can be used for other purposes than
28 The changes add four new profile components:
30 add-hook: This is the full pathname of a program that is invoked
31 whenever a message is added to a folder. The program
32 is passed one argument which is the full pathname of the
33 message file. The program is executed after the message
34 is written so that it can act upon that message.
36 del-hook: This is the full pathname of a program that is invoked
37 whenever a message is deleted from a folder. The program
38 is passed one argument which is the full pathname of the
39 message file. The program is executed before the message
40 is written so that it can act upon that message.
42 ref-hook: This is the full pathname of a program that is invoked
43 whenever a message is refiled. The program is passed two
44 arguments: the first is the full pathname of the original
45 message file, the second is the full pathname of the final
46 message file. The program is executed after the message
49 msg-hook: This is a text message that is output if the execution of
50 one of the external hook programs fails. There is a built-in
51 default message if none is specified.
53 The definition of refiling is a bit tricky. The refile hook is executed if a
54 message is moved from one place to another. So, for example, the command
58 causes the add hook to be executed, not the refile hook, because a new message
59 is created, the old one isn't moved.
61 These changes affect the following commands:
63 burst: The add hook is executed for messages burst from a digest, and
64 for the table of contents if -inplace is specified. The delete
65 hook is executed for the original message if -inplace is
66 specified. The refile hook is executed for messages that are
69 folder: The refile hook is executed for -pack.
71 inc: The add hook is executed when messages are incorporated.
73 refile: Either the add or refile hooks are executed.
75 rmf: The delete hook is executed when messages are deleted.
77 rmm: The delete hook is executed when messages are deleted.
79 sortm: The refile hook is executed for each message moved. Note that
80 a magic temporary message number of 2147483647 is used to hold
81 messages as they are being shuffled.
85 Did I Do This Correctly?
86 ~~~~~~~~~~~~~~~~~~~~~~~~
88 Well, sort of. This all works, but I'm not really happy with it. The issue
89 is that an examination of the nmh code shows that message handling is scattered
90 all over the place. Although there are library routines such as folder_addmsg
91 and folder_delmsgs, they are not used consistently. Long term, I think that it
92 would be better to make all message handling go through the same choke points.
94 Also, I added a function to run the external programs. This sort of stuff is
95 also scattered around the nmh code, for example in the code to run the rmmproc.
96 Again, I'd like to make this more consistent in the long term.
98 What Files Did I Change?
99 ~~~~~~~~~~~~~~~~~~~~~~~~
111 ext_hook.c (new file)