Cameron Laird's personal notes on procmail

I launched this page to amplify our cover story for the December 1997 Sunworld and the chapter on "Automation" in the second edition of ..., as a service to their readers. While the former article focuses first on combatting spam, both these pieces discuss positive uses for procmail. [explain] You're welcome also to read other articles we've written, including Procmail 'Passthrough' Partners for Powerful E-mail Filtering and [... Oct 2001 OS on filtering ...].

Procmail documents:

Jari Aalto's Procmail tips page includes such gems as "subroutines" for grabbing MIME information into procmail variables,
Catherine A. Hampton's Getting Started With Procmail,
era eriksson's Procmail FAQ, with special attention to its
Procmail links page,
Nancy McGough's Filtering Mail FAQ, and
Ian Soboroff's "Mail Filtering with Procmail".

Favorite Filters I Have Known include ones [annotate] from

Craig Johnston (e-mail Craig at caj@praline.no.neosoft.com),
Dougal Campbell's anti-spam procmail rules,
"But shun profane [and] vain babblings ...", as the King James Version translates 2 Timothy 2:16,
... [more to come]

Procmail is easy to set up. The most delicate aspect of a first filter is writing the .forward precisely. Here are a few variations I've encountered:

BSDI: "|IFS=' ' && exec /usr/local/bin/procmail -f- || exit 75 #claird"
Digital Unix:
FreeBSD:
Linux: most (all modern?) Linux installations condition on the presence of $HOME/.procmailrc for procmail processing. There is no need to write a .forward. It's still correct, though, to write "|IFS=' ' && exec /usr/local/bin/procmail -f- || exit 75 #claird"
Solaris: "|IFS=' ' && exec /usr/bin/procmail -f- || exit 75 #claird"

I have a regret about the article; it is that we didn't say a few more words about the $HOME/.procmail/log file where procmail records its activity. If procmail is doing something different from what you expect, or you want to develop metrics on what procmail does for you, or you just want to understand its operation better, browse the log. Also, be aware that procmail logs can become big; many procmail users periodically erase/archive/replace/... their logs.

Thanks to Richard Hanby and Ric Steinberger who caught the out-of-place '$' in the original release of the article. Thanks also to Jari Aalto, who wisely recommended we should warn readers that

As a precaution, always set SHELL=/bin/sh at the beginning of your .procmailrc. This is a good safety measure.

Jari adds that PATH is also a candidate for explicit definition.

Cameron Laird's personal notes on procmail/claird@phaseit.net