Re: Looking for a regular expression for the following pattern.

So is it alway an underscore after 2 characters?

Otherwise this should do:

/^[a-z0-9_]+$/i
[download]

s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e

Comment on Re: Looking for a regular expression for the following pattern. Select or Download Code

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Re^2: Looking for a regular expression for the following pattern. by ikegami (Patriarch) on Mar 29, 2018 at 12:37 UTC
That matches "_" and "a\n"	[reply]
Re^3: Looking for a regular expression for the following pattern. by Skeeve (Parson) on Mar 29, 2018 at 14:06 UTC
OP didn't say anything about linefeeds so it's safe to assume they can be ignored OP didn't say that "_" is not allowed. It's "alphanumeric characters with underscores, one or more" OP's post is poorly written so expect a poorly written reply ;) `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]
Re^4: Looking for a regular expression for the following pattern. by Laurent_R (Canon) on Mar 29, 2018 at 16:03 UTC
It is true that the OP is not specific enough (far from that), but if you're suggesting `/^[a-z0-9_]+$/i`, you might as well suggest `/^\w+$/`. And this is even less specific than the examples shown by the OP.	[reply] [d/l] [select]