How to find patterns across multiple lines using grep?

Solution:

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

I'm not sure if it is possible with grep, but sed makes it very easy:

sed -e '/abc/,/efg/!d' [file-with-content]

Here is a solution inspired by this answer:

  • if 'abc' and 'efg' can be on the same line:

      grep -zl 'abc.*efg' <your list of files>
    
  • if 'abc' and 'efg' must be on different lines:

      grep -Pzl '(?s)abc.*\n.*efg' <your list of files>
    

Params:

  • -P Use perl compatible regular expressions (PCRE).

  • -z Treat the input as a set of lines, each terminated by a zero byte instead of a newline. i.e. grep treats the input as a one big line.

  • -l list matching filenames only.

  • (?s) activate PCRE_DOTALL, which means that '.' finds any character or newline.