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

I needed to find all the files that contained a specific string pattern. The first solution that comes to mind is using find piped with xargs grep:

find . -iname '*.py' | xargs grep -e 'YOUR_PATTERN'

But if I need to find patterns that spans on more than one line, I'm stuck because vanilla grep can't find multiline patterns.

Why don't you go for awk:

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

Here is the example using GNU grep:

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

> -z/--null-data Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline.

Which has the effect of treating the whole file as one large line. See description here

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

> the -M option makes it possible to search for patterns that span line boundaries.

For example, you need to find files where the '_name' variable is followed on the next line 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', ...

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

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 

With silver searcher:

ag 'abc.*(\n|.)*efg'

Speed optimizations of silver searcher could possibly shine here.

@Marcin: awk example non-greedy:

awk '{if ($0 ~ /Start pattern/) {triggered=1;}if (triggered) {print; if ($0 ~ /End pattern/) { exit;}}}' filename

You can use the grep alternative sift here (disclaimer: I am the author).

It support multiline matching and limiting the search to specific file types out of the box:

sift -m --files '*.py' 'YOUR_PATTERN'

(search all *.py files for the specified multiline regex pattern)

It is available for all major operating systems. Take a look at the samples page to see how it can be used to to extract multiline values from an XML file.

This answer might be useful:

https://stackoverflow.com/questions/3717772/regex-grep-for-multi-line-search-needed/7167115#7167115

To find recursively you can use flags -R (recursive) and --include (GLOB pattern). See:

https://stackoverflow.com/questions/221921/grep-exclude-include-syntax-do-not-grep-through-certain-files/221929#221929

perl -ne 'print if (/begin pattern/../end pattern/)' filename

Using ex/vi editor and globstar option (syntax similar to awk and sed):

ex +"/string1/,/string3/p" -R -scq! file.txt

where aaa is your starting point, and bbb is your ending text.

To search recursively, try:

ex +"/aaa/,/bbb/p" -scq! **/*.py

^{Note: To enable ** syntax, run shopt -s globstar (Bash 4 or zsh).}