Optional leading character on multine pattern

Elastic Stack Beats
1

Hello.
I am process log files with filebeats and have come across a format that starts a multi line mess that may or may not have a character before the timestamp.

eg.
Normal: "[20170126,"
New case: "[20170126,"

I was using the pattern below and am asking for help in modifying it to understand either pattern as starting a new multiline.

multiline:
pattern: '^[[:digit:]]{4}[[:digit:]]{2}[[:digit:]]{2},'

thank you

2

not sure I'm missing something, but I see no difference in the Normal and the New case here. An optional match can be expressed with <term>? meaning, match zero or one time.

3

You're right Steffen. bad copy / paste.

Normal is [20170126,
Optional case is <feff>[20170126,.

thank you for your suggestion despite my miscommunication.

after replying and same thing happening I understand. the optional text is disappearing in entry box here. It is < f e f f > (without spaces).

4

You can escape code using backtick or the </> button.

Sorry, have to ask again, so the optional is <feff>[20170126,? like is <feff> just one character?

Are you using windows? This looks like an utf16 BOM flag. The BOM flag normally appears at beginning of file only. Can you share your prospectors configuration?