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regexpcre

Regex Remove non matching line while substituting

Given this text string of ; delimited columns:

a;b;c
a;x;23
b;b;12

I am looking to get column 3 of every line that has an a in column 1 with ^(a);(.*?);(.*?)$ as shown here.

However, as you can see the full non matching line, is also present in the result, after the substitution.

Any idea on how to get only the 3rd column of the matching lines, without the non matching one.

Thanks

Solution

  • You may add a .* alternative to just match the line if the first alternative does not match:

    ^(?:(a);(.*?);(.*?)|.*)$
 ^^^               ^^^

    See the regex demo

    NOTE: If there is a requirement to only match two semi-colons in the string, you need to use [^;]* instead of .*?:

    ^(?:(a);([^;]*);([^;]*)|.*)$

    See this regex demo (\n added to the negated character class in the demo to account for the fact that the regex test is performed on a single multiline string, not a set of separate strings).