How to find patterns across multiple lines using grep?

Question

I want to find files that have \"abc\" AND \"efg\" in that order, and those two strings are on different lines in that file. Eg: a file with content:

blah bl         


        

Answer 1

I relied heavily on pcregrep, but with newer grep you do not need to install pcregrep for many of its features. Just use grep -P.

In the example of the OP's question, I think the following options work nicely, with the second best matching how I understand the question:

grep -Pzo "abc(.|\n)*efg" /tmp/tes*
grep -Pzl "abc(.|\n)*efg" /tmp/tes*

I copied the text as /tmp/test1 and deleted the 'g' and saved as /tmp/test2. Here is the output showing that the first shows the matched string and the second shows only the filename (typical -o is to show match and typical -l is to show only filename). Note that the 'z' is necessary for multiline and the '(.|\n)' means to match either 'anything other than newline' or 'newline' - i.e. anything:

user@host:~$ grep -Pzo "abc(.|\n)*efg" /tmp/tes*
/tmp/test1:abc blah
blah blah..
blah blah..
blah blah..
blah efg
user@host:~$ grep -Pzl "abc(.|\n)*efg" /tmp/tes*
/tmp/test1

To determine if your version is new enough, run man grep and see if something similar to this appears near the top:

   -P, --perl-regexp
          Interpret  PATTERN  as a Perl regular expression (PCRE, see
          below).  This is highly experimental and grep -P may warn of
          unimplemented features.

That is from GNU grep 2.10.