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Take the following file :

aaa
bbb
XXX
ccc
ddd
eee
XXX
fff
ggg

I'd like to print, with pcregrep, all lines until the first one containing XXX :

aaa
bbb
XXX

Is it possible (with pcregrep or pcre2grep) ?

I achieved this :

$ pcre2grep -nM '(.|\n)*?XXX' file
1:aaa
bbb
XXX
4:ccc
ddd
eee
XXX

Is there a way to quit after the first match ? It seems that pcre2grep doesn't have a --max-count option like grep has.

Nota : I'm aware that there are better tools to get the desired result (sed, among others), but I'm not looking for alternate solutions here. My question is about pcregrep or pcre2grep, I'd like to know if there is a way to emulate grep's --max-count option.

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  • Why do you want to use pcregrep? GNU grep supports pcre-like regexes via the -P option.
    – user313992
    Oct 16, 2021 at 15:19
  • pcregrep and pcre2grep support multiline matching with -M, grep does not. Feb 5 at 18:11

1 Answer 1

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As you are using Debian 9 (Stretch), you have the version of pcre2-utils which includes pcre2grep 10.22. That version doesn't include the -m or --max-count option to quit after a certain number of matches. With that being said, what you are trying to do, print up to a string, simply isn't possible with the version that you have.

The version that comes with Debian 11 (Bullseye), 10.34, does have this option. You can use it on the file that you have to achieve the expected output with the following:

pcre2grep -B2 -m1 XXX file

You can also do it with regular grep as there's no need to use Perl-compatible regular expressions for your case:

grep -B2 -m1 XXX file

The -n option isn't needed as it just prints the line number which isn't in your expected output and the -M option conflicts with the -m option because the former tells it to match multiple lines.

Output of the above commands:

aaa
bbb
XXX

That prints up to the first match of the string XXX and also the two lines before it; however, I wouldn't recommend this because you'd have to know exactly how many lines appear from the beginning of the line until the string. That might not be an issue for your particular file but would be if the file were to contain thousands or millions of lines.

What you trying to do, in effect, is to print everything from the beginning of the file up to and including a certain string. Neither grep or any of its derivatives such pcre2grep are designed to do this and don't have options to get this result in a dependable manner on their own. It is for this reason that it's better to use a tool that is actually designed to achieve this such as sed or awk which I've previously mentioned. They are both far more reliable and easier to use to get what you want and don't require any doctoring or having to know exactly how many lines come before where you want the output to stop. You may have gone into this with the intention of using pcre2grep but it's important to recognize that there are better options and use one of those.

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