CODEWITHSUNDEEP
regexregex-lookarounds
Michal Freiwald
Michal Freiwald

Reputation: 1

regex: If "/" is found in line, Ingore string up until "/" and match everything after

I'm new to all this, so apologies for any inaccuracies.

I'm trying to write a regex that looks for "/" in a line at a specific position. If it is found, it should ignore everything before and match everything after.

So far, I've come up with

^(?(?=^.{6}[\/])[a-zA-Z0-9\_\-]+|\n)

but it seems to be doing the exact opposite; if "/" is found at the 7. position, it matches everything before "/". I got inspired by different threads, yet I'm still unable to make it work.

Any thoughts on what am I doing wrong?

Upvotes: 0

Views: 487

Answers (1)

The fourth bird
The fourth bird

Reputation: 163632

The pattern ^(?(?=^.{6}[\/])[a-zA-Z0-9\_\-]+|\n) uses an if clause, where in the if part there is an assertion for 6 characters followed by a /

The assertion is at the start of the string, and does not consume characters. If that assertion is true, then match either [a-zA-Z0-9\_\-]+ or a newline, so the consuming parts starts there and that is why you get that match.

It matches the first 6 characters and not the / because that is not in the character class.

You can use a capture group to match all allowed characters after the / at the 7th position.

^.{6}\/([a-zA-Z0-9_-]*)
  • ^ Start of string
  • .{6}\/ Match 6 characters and /
  • ([a-zA-Z0-9_-]*) Capture group 1, optionally match any of the listed in the character class

Regex demo

Or if supported you can use \K to forget what is matched so far:

^.{6}\/\K[a-zA-Z0-9_-]*
  • ^ Start of string
  • .{6}\/ Match 6 characters and /
  • \K Clear the match buffer (forget what is matched until now)
  • [a-zA-Z0-9_-]* Optionally match any of the listed in the character class

Regex demo

Upvotes: 3

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