How to find patterns across multiple lines using grep?

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 bl         


        

Answer 1

With ugrep released a few months ago:

ugrep 'abc(\n|.)+?efg'

This tool is highly optimized for speed. It's also GNU/BSD/PCRE-grep compatible.

Note that we should use a lazy repetition +?, unless you want to match all lines with efg together until the last efg in the file.

Answer 2

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 3

#!/bin/bash
shopt -s nullglob
for file in *
do
 r=$(awk '/abc/{f=1}/efg/{g=1;exit}END{print g&&f ?1:0}' file)
 if [ "$r" -eq 1 ];then
   echo "Found pattern in $file"
 else
   echo "not found"
 fi
done

Answer 4

This should work:

cat FILE | egrep 'abc|efg'

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

Answer 5

Why not something simple like:

egrep -o 'abc|efg' $file | grep -A1 abc | grep efg | wc -l

returns 0 or a positive integer.

egrep -o (Only shows matches, trick: multiple matches on the same line produce multi-line output as if they are on different lines)

• grep -A1 abc (print abc and the line after it)

• grep efg | wc -l (0-n count of efg lines found after abc on the same or following lines, result can be used in an 'if")

• grep can be changed to egrep etc. if pattern matching is needed

Answer 6

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.