[Much of this documentation is cloned from doc/advanced.txt in the owl repository]

BarnOwl supports an expressive filter language that can be used to describe sets of messages. This language is used both for coloring messages and for selectively viewing subsets of your messages.

The following command will create a filter called 'mail' that maches any messages sent to the zephyr class 'mail':

filter mail class ^mail$

The first argument after the filter command specifies the name of the filter to be created. The text after that indicates that matching messages must have the zephyr class "mail". For help understanding the ^ and $ characters, consult a reference on POSIX regular expressions, such as man 7 regex or an ​online version. Note that all pattern matching in Barnowl is case-insensitive.

The message fields that can be used in a filter command include:

sender

message sender

recipient

message recipient

class

zephyr class name

instance

zephyr instance name

opcode

zephyr opcode

realm

zephyr realm

body

message body

type

message type ('zephyr', 'aim', 'admin', ...)

direction

either 'in' 'out' or 'none'\n"

login

either 'login' 'logout' or 'none'\n"

The info command (bound to i by default) includes a list of “Owl Message Attributes”; Any attribute listed in this area can also be matched on by a filter.

A filter can refer to other filters using the filter command:

filter somefilt filter foo or filter bar

Would match anything in either the foo or bar filters. Recursive filters are explicitly disallowed.

You can also use the operators 'and' 'or' and 'not' as well as the values 'true' and 'false'. Parentheses can be used to group expressions, though there must be spaces present before and after all parenthesis. For example:

filter myfilt ( class ^foo$ ) or ( class ^quux$ and instance ^bar$ )

If you define a filter using a filter name that already exists, it will overwrite the existing filter. This can be a useful way to override the built-in filters.

Built-in special filters

all

Matches all messages

none

Matches no messages

personal

“personal” messages, messages sent privately to you.

login

Login/Logout notifications

auto

Messages generated by automated programs

out

Messages sent from you to another user

aim

AIM messages

zephyr

Zephyr messages

trash

"Trash" messages

ping

Zephyr pings reply-lockout Messages for which the reply commands should not work

The trash filter is used for the delete trash command (bound to T). That command will mark as deleted (but not expunge) all messages in the trash filter. By default, this filter matches messages on -c mail, admin messages, pings, and login notifications.

The reply-lockout filter can be used to prevent you from accidentally replying to classes you do not want to ever send to. By default it includes class mail and class noc, both of which are used for automatic notifications but which users generally never send to themselves.