How to escape a parenthesis when using rex to create a field?

[Splunkster45]

I have a question about extracting two fields from the below sample text

Session <number> (<username>@<ipaddress>) started

I would like to be able to store the variable number and username as a field, but I am running into issues with the '('. Whenever I run the command, I get an error message saying that I am missing a ')'

Here is the command that I am using

| rex field=_raw "Session (?<number><backslash>w+) ((?<username><backslash>w+)@"

The number is either a 4 or 5 digit number and the username is always 6 characters. I do not care about the IP address.

How can I escape the parenthesis? I've done a little bit of searching and found a question that asked about escaping a '(' in a macro, but either that didn't apply or I couldn't follow it.

Thanks in advance!

[jrodman · Accepted solution]

In PCRE regexes (which Splunk uses), punctuation preceded by a backslash always matches the punctuation, so \( matches a (.
Parens without a backslash form groups as you are using to find your number. There is a bit of a trick though, because the search language also uses backslashes for escaping. Therefore I would suggest

 | rex field=_raw "Session (?<number>\\w+) (?<username>\\(\\w+)@"

[Splunkster45]

Thanks! I modified your search command to the following and it worked perfectly

| rex field=_raw "Session (?\\w+) \\((?\\w+)@"

[jrodman]

Ah, seems I slightly misunderstood the goal. In retrospect it should have been obvious. Glad it's working.