Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual page 422

Chapter 24. Email
• > — Checks if the message is over a specified number of bytes.
The following characters are used to perform special actions:
• ! — In the action line, this character tells Procmail to forward the message to the specified email
addresses.
• $ — Refers to a variable set earlier in the rc file. This is often used to set a common mailbox that is
referred to by various recipes.
• | — Starts a specified program to process the message.
• { and } — Constructs a nesting block, used to contain additional recipes to apply to matching
messages.
If no special character is used at the beginning of the action line, Procmail assumes that the action line
is specifying the mailbox in which to write the message.
24.5.2.5. Recipe Examples
Procmail is an extremely flexible program, but as a result of this flexibility, composing Procmail recipes
from scratch can be difficult for new users.
The best way to develop the skills to build Procmail recipe conditions stems from a strong
understanding of regular expressions combined with looking at many examples built by others.
A thorough explanation of regular expressions is beyond the scope of this section. The structure
of Procmail recipes and useful sample Procmail recipes can be found at various places on the
Internet (such as http://www.iki.fi/era/procmail/links.html). The proper use and adaptation of regular
expressions can be derived by viewing these recipe examples. In addition, introductory information
about basic regular expression rules can be found in the grep man page.
The following simple examples demonstrate the basic structure of Procmail recipes and can provide
the foundation for more intricate constructions.
A basic recipe may not even contain conditions, as is illustrated in the following example:
:0:
new-mail.spool
The first line specifies that a local lockfile is to be created but does not specify a name, so Procmail
uses the destination file name and appends the value specified in the LOCKEXT environment variable.
No condition is specified, so every message matches this recipe and is placed in the single spool file
called new-mail.spool, located within the directory specified by the MAILDIR environment variable.
An MUA can then view messages in this file.
A basic recipe, such as this, can be placed at the end of all rc files to direct messages to a default
location.
The following example matched messages from a specific email address and throws them away.
:0
* ^From: spammer@domain.com
/dev/null
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