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If you'd like to learn more about such grep powers, check out my free ebook [0] What do you mean by "reverse \K"? Are you aware of lookarounds? Perhaps you mea

• mxmkm 4y ago
  In vim there is `\zs` and `\ze` where `\zs` is the `\K` equivalent in grep. Basically :%s/hello \zsworld\ze out there/planet/g would find all `hello world out there` and replace `world` to `planet`.
• Joker_vD 4y ago
  Consider this: grep -P 'start: (\d+) end' "How do I make it print only the captured group with the number, not the whole line?" is a pretty common Stack Overflow question. The "\K" thing gets rid of the "start: " part, but what about " end"? That's were "reverse \K" would come in handy.
  • asicsp 4y ago
    That's where lookarounds help: grep -oP 'start: \K\d+(?= end)' `\K` is kinda similar to lookbehind (but not exactly same as it is not zero-width), and particularly helpful for variable length patterns. If you need to process further, you can make use of `-r` option in `ripgrep` or move to other tools like sed, awk, perl, etc.
  • burntsushi 4y ago
    That's where ripgrep's -r/--replace flag comes in handy: $ echo 'foobar start: 123 end quuxbar' | rg 'start: ([0-9]+) end' foobar start: 123 end quuxbar $ echo 'foobar start: 123 end quuxbar' | rg 'start: ([0-9]+) end' -r '$1' foobar 123 quuxbar $ echo 'foobar start: 123 end quuxbar' | rg 'start: ([0-9]+) end' -or '$1' 123