How can I search for a multiline pattern in a file?

Solution 1:

Why don't you go for awk:

awk '/Start pattern/,/End pattern/' filename

Solution 2:

So I discovered pcregrep which stands for Perl Compatible Regular Expressions GREP.

For example, you need to find files where the '_name' variable is immediatelly followed by the '_description' variable:

find . -iname '*.py' | xargs pcregrep -M '_name.*\n.*_description'

Tip: you need to include the line break character in your pattern. Depending on your platform, it could be '\n', \r', '\r\n', ...

Solution 3:

Here is the example using GNU grep:

grep -Pzo '_name.*\n.*_description'

-z/--null-data Treat input and output data as sequences of lines.

Solution 4:

grep -P also uses libpcre, but is much more widely installed. To find a complete title section of an html document, even if it spans multiple lines, you can use this:

grep -P '(?s)<title>.*</title>' example.html

Since the PCRE project implements to the perl standard, use the perl documentation for reference:

http://perldoc.perl.org/perlre.html#Modifiers
http://perldoc.perl.org/perlre.html#Extended-Patterns

Solution 5:

Here is a more useful example:

pcregrep -Mi "<title>(.*\n){0,5}</title>" afile.html

It searches the title tag in a html file even if it spans up to 5 lines.

Here is an example of unlimited lines:

pcregrep -Mi "(?s)<title>.*</title>" example.html