Creating custom regex triggers (MessageParser)

In addition to creating custom commands using the Aka plugin, Limnoria also allows you to create custom, regular expression based message triggers using the MessageParser plugin.

Before proceeding through this page, we recommend reading the Command parsing primer, which discusses many of the details that apply to running commands via message triggers.

Creating & managing regex triggers

Regex triggers are created using the messageparser add command:

<user> @messageparser add "some words" "echo Blah blah"
<Limnoria> Done.
[...]
<user> I am saying some words.
<Limnoria> Blah blah

messageparser list will show a list of configured triggers, and messageparser remove will remove them:

<user> @messageparser list
<Limnoria> #1: some words
<user> @messageparser remove --id 1
<Limnoria> Done.

In practice, it’s usually easier to remove a trigger by its ID instead of repeating out the regex in full, since you may have to escape symbols within the expression otherwise.

Case sensitivity

To make a trigger case-insensitive, preface it with the (?i) modifier:

<user> @messageparser add "(?i)^test$" "echo Test failed, try again later"
<Limnoria> Done.
<user> TEST
<Limnoria> Test failed, try again later

Extracting parameters from capture groups

When the regular expression has a capture group, its content will be passed in as $1, $2, etc. in a similar way to command aliases:

<user> @messageparser add "define (.+)" "dict $1"
<Limnoria> Done.
[...]
<user> define ice cream
<Limnoria> wn: ice cream n 1: frozen dessert containing cream and sugar and flavoring [syn: {ice cream}, {icecream}]

The dict [<dictionary>] <word> command in this example is provided by the Dict plugin.

Example: run commands sent through relay bots

One practical use of MessageParser may be to make Limnoria run messages sent by other relay bots, as these would normally not match Limnoria’s command prefix. For example, if your bot uses “!” as its command prefix and you have a relay bot that sends text in the format:

<RelayBot> [othernetwork] <user> hi

You could add a MessageParser trigger like this:

<user> @messageparser add "^\[.*?\] <.*?> !(.*)$" "apply $1"
<Limnoria> Done.
<RelayBot> [othernetwork] <user> !echo hello world
<Limnoria> hello world

This would read all messages sent over the relay bot that start with a “!”, and run them as a command via apply <command> <text>.

Note that in this case, all relayed commands will be treated as if RelayBot itself ran it, so there is no fine grained access control.

Limitations

Custom command triggers are not designed to replace plugins in all cases. The same limitations for the Aka plugin apply here as well.