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=One-Liners=
Case insensitive search
grep -i "the" demo_file
Checking for full words, not for sub-strings
grep -iw "is" demo_file
Display N lines after, before, around match
grep -A 3 -i "example" demo_text # After Match
grep -B 2 "single WORD" demo_text # Before Match
grep -C 2 "Example" demo_text # Around Match
Color Filtered Output
grep "Gecko" /data --color=always
Highlighting the search using GREP_OPTIONS
export GREP_OPTIONS='--color=auto' GREP_COLOR='100;8'
Recursive Search
grep -r "test" *
Recursively but ignore binary files
grep -rI "test" someDir/
Invert match
grep -v "go" demo_text
grep -v -e "a" -e "b" -e "c" test-file.txt
How many lines matches the given pattern
grep -c "go" demo_text
How many lines that does not match the pattern
grep -v -c this demo_file
Display only the file names which matches the given pattern
grep -l this demo_*
Show only the matched string
grep -o "is.*line" demo_file
Show line number while displaying the output
grep -n "go" demo_text
Filter comments from a config file
<nowiki>grep -vE '^#|^;|^$' server.conf</nowiki>
Search for "virus" in all files in a dir
grep virus /etc/snort/rules/*
Search this or that using Extended Regex
<nowiki>grep -E '(then|there)' demo_text</nowiki>
Search this or that without Extended Regex
<nowiki>grep '\(then\|there\)' demo_text</nowiki>
Search this or that grouping not necessary
<nowiki>grep 'then\|there' demo_text</nowiki>
Search this or that grouping required
<nowiki>grep 'the\(n\|re\)' demo_text</nowiki>
Search Email addresses using regex
<nowiki>grep -E -o "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b" filename.txt</nowiki>
Grep from compressed files
zgrep -I "free space" ./messages*
Print lines which begin with "foo" and end in "bar"
grep "^foo.*bar$" file.txt
Filter the Filtered output:
grep "test" file.txt | grep -v "pass"
Search for the string and not the regex:
fgrep "foobar" file.txt
grep -F "foobar" file.txt
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