How to find patterns across multiple lines using g

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

Should be matched.

Answer 1

If you are willing to use contexts, this could be achieved by typing

grep -A 500 abc test.txt | grep -B 500 efg

This will display everything between "abc" and "efg", as long as they are within 500 lines of each other.

Answer 2

awk one-liner:

awk '/abc/,/efg/' [file-with-content]

Answer 3

This should work:

cat FILE | egrep 'abc|efg'

If there is more than one match you can filter out using grep -v

Answer 4

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

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

Answer 5

I released a grep alternative a few days ago that does support this directly, either via multiline matching or using conditions - hopefully it is useful for some people searching here. This is what the commands for the example would look like:

Multiline: sift -lm 'abc.*efg' testfile
Conditions: sift -l 'abc' testfile --followed-by 'efg'

You could also specify that 'efg' has to follow 'abc' within a certain number of lines:
sift -l 'abc' testfile --followed-within 5:'efg'

You can find more information on sift-tool.org.

Answer 6

This can be done easily by first using tr to replace the newlines with some other character:

tr '\n' '\a' | grep 'abc.*def' | tr '\a' '\n'

Here, I am using the alarm character, \a (ASCII 7) in place of a newline. This is almost never found in your text, and grep can match it with a ., or match it specifically with \a.