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How can I specify a regex in a zgrep/zcat command?

J.erome

I want to find in a list of words, every words with a least 3 times the same letter in it. To achieve that I did .*(w).*1.*1.*1.* and you can test it here http://www.regexplanet.com/advanced/java/index.html but I don’t know how to put it in my zgrep command.

How can I insert this regex in a zgrep command ?

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Answer

A couple of notes:

  • You do not need to match start and end of a line with .* since partial matches are allowed
  • w matches letters, digits and underscores in NFA regex patterns, in POSIX, it is safer to use [[:alnum:]_]
  • To form a capturing group in a POSIX BRE pattern use escaped parentheses, (...).

Thus, use

zgrep '([[:alnum:]_]).*1.*1.*1' a.gz

Or, contract it a bit since it looks a bit redundant with three consecutive .*1 subpatterns:

zgrep '([[:alnum:]_])(.*1){3}' a.gz