Grep - Cheatsheet

# Grep tab using Perl regex
    grep -P "\t"
 
# Select multiple text patterns(e.g "this" or "that")
    grep -E "this|that"
 
# Grep either pattern1 or pattern2.
    grep -e '(pattern1)|(pattern2)'
    grep '\(pattern1\)\|\(pattern2\)'
 
# Searches in files recursively through directories for pattern, 
#  while ignoring filename containing ignoreString
    grep pattern $(find . -type f | grep -v 'ignoreString')
    grep pattern $(find . -name '*.txt' -or -name '*.java' | grep -v 'ignoreString')
    grep -E -rn "Your search string" /location/
 
# Show 15 lines before and after
    grep -C 15
 
# Show row number.  
    echo -e "one\ntwo"| grep -n ^
 
# Show all but highlight pattern found.  
    echo -e "one\ntwo\nthree"| grep -E 'e|$'
 
# Show all lines and highlight pattern.
    grep -E '^|pattern' file
 
# Color match term
    grep --color=auto
 
# Grep whitespaces up to pound key(#)
    grep -v "^[[:space:]]*#"
 
# Grep 3 digits.
    echo 1459mmmm34mm | grep -E [0-9]{3}
    echo 2786mmmm34mm | grep -E [[:digit:]]{3}
 
# Grep dash / hyphen.
    echo -e "--x---t--\nas" | grep -E '[\-]{2}'
 
# Count number of occurrence found. Number of CPUs.
    grep -c ^processor /proc/cpuinfo