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grep Command.md

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grep Command.md

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grep command

grep :- The grep command is a powerful text search utility commonly found in Unix-like operating systems.It allows you to search for specific patterns or regular expressions within files or input streams and print the matching lines.

  • grep :- Search for a specific word in a file.

    grep "apple" file.txt

grep command switch

  • -i :- Search for a pattern case-insensitively and display line numbers.

    grep -i "apple" file.txt

  • -v :- Invert the match. Display lines that do not match the pattern.

    grep -v "apple" file.txt

  • -E :- let's use the grep -E command to search for lines that contain words starting with either "ap" or "gr.

    grep -E "(ap|gr)" data.txt

  • -r :- Search for a pattern recursively in a directory.

    grep -r "pattern" directory/

  • -l :- Only list the names of files that contain the pattern.

    grep -l "apple" directory/

  • -n :- Print line numbers along with the matching lines.

    grep -n "apple" file.txt

  • -w :- Match whole words only.

    grep -w "apple" file.txt

Examples :

  • grep “pattern search” file.txt 

  • grep -i “pattern search”  file.txt

  • grep -E “( pattern1 | pattern2 )” file.txt			

  • grep -E “( pattern search1 | pattern search2 )” file.txt

  • grep -E "( localhost journal | localhost kernel )" messages  			

  • grep -E "( localhost journal | localhost kernel )" messages | grep failed

  • grep -v “localhost kernel” messages 	

  • grep root. messages 	

  • grep "root\." messages 

  • grep root\. messages

  • grep root\.$ messages 	

  • grep “^Jun 1 ” messages 	

  • grep -E "( localhost journal | localhost kernel )" messages | grep -E "( OK | failed )"

  • grep -E "( localhost journal | localhost kernel )" messages | grep -vE "( OK | failed )"

  • grep "^#" sshd_config

  • grep -v "^#" sshd_config

  • grep -vE "( ^# | ^$ )" etc/ssh/sshd_config

  • grep -E "( ^# | ^$ )" etc/ssh/sshd_config

  • grep “^$” etc/ssh/sshd_config 		

  • grep -v “^$” etc/ssh/sshd_config 			

  • grep -vE "( ^# | ^$ )" etc/yum.conf | grep s.

  • grep -vE "( ^# | ^$ )" etc/yum.conf | grep s.*	

  • grep -vE "( ^# | ^$ )" etc/yum.conf | grep [sa]		

  • grep -vE "( ^# | ^$ )" etc/yum.conf | grep [0-9]

  • grep -vE "( ^# | ^$ )" etc/yum.conf | grep [a-z]	

  • grep [0-9] user.txt		 

  • grep [123] user.txt		 

  • grep “123” user.txt		 

  • grep [0123456789] user.txt			 

  • grep [0-9] [0-9] user.txt				 

  • grep [0-9] [0-9] [0-9] user.txt	 

  • grep [A-Z] user.txt							 

  • grep -o "localhost" messages 	 	

  • grep root *											 

  • grep -Rn root /etc 								 

  • grep -l root /etc 									 

  • grep "^./Desktop" file.txt