How to find patterns across multiple lines using grep?

regex grep

Saobi · Apr 21, 2010 · Viewed 290.6k times · Source

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 blah..
blah blah..
blah abc blah
blah blah..
blah blah..
blah blah..
blah efg blah blah
blah blah..
blah blah..

Should be matched.

Answer

Grep is not sufficient for this operation.

pcregrep which is found in most of the modern Linux systems can be used as

pcregrep -M  'abc.*(\n|.)*efg' test.txt

where -M, --multiline allow patterns to match more than one line

There is a newer pcre2grep also. Both are provided by the PCRE project.

pcre2grep is available for Mac OS X via Mac Ports as part of port pcre2:

% sudo port install pcre2

and via Homebrew as:

% brew install pcre

or for pcre2

% brew install pcre2

pcre2grep is also available on Linux (Ubuntu 18.04+)

$ sudo apt install pcre2-utils # PCRE2
$ sudo apt install pcregrep    # Older PCRE