Advanced GREP

1. Recursive Search

-R searches all files and dirs in the directory.

 grep -R "search_text" /home/user/

2. Search doesn’t include

-v displays lines that do not match the pattern.

grep -v "search_text" filename

3. Count

-c returns the number of lines that match the pattern.

grep -c "search_text" filename

4. Line Number

-n displays the line numbers with output lines.

grep -n "search_text" filename

5. Ignore capitaliztion

-I makes the search case insensitive.

grep -i "search_text" filename

6. Extended Regexp

-E lets you use additional regular expression features.

grep -E 'pattern1|pattern2' filename

This command will search for lines containing either “pattern1” or “pattern2”.

7. File pattern

-include, —exclude specify search based on filename.

grep -R --include="*.txt" "search_text" /home/user/

This will search recursively but only look files ending with “.txt”.

8. Word-Regexp

-w only returns lines where the pattern matches the whole “word”.

grep -w "search_text" filename

In you’re looking for “log”, it won’t return “blog” or “logic” because “log” is not a whole word in these instances.

9. After & Before

Print the lines that appear after (-A), before (-B), or on either side (-C) of the matching pattern.

grep -A 5 -B 5 "search_text" filename

This command will print out 5 lines before and after each line that matches “search_text”.