Grep command in linux explained
Grep command used for search files and search pattern.
grep [options] pattern [files]
Options Description
-c : counts the frequency only
-h : Display the matched lines, but do not display the filenames.
-i : case insensitive Ignores, case for matching
-l : filenames only.(imp)
-n : line number if word in a file
-v : lines that are not matched with the keyword
-e exp : Specifies expression with this option. Can use multiple times.
-f file : takes the file patterns
-E : Treats pattern as an extended regular expression (ERE)
-w : prints whole words in a file
-o : Print only matched words per line
Expressions
Start ^
End $
grep “^linux” mynewfile.txt
grep “ux$” mynewfile.txt
$grep –e “admin” –e “admin” –e “admin” newfile.txt
$grep –f newfile.txt mynewfile.txt
grep ‘word’ file1 file2 file3
grep -n ‘root’ /etc/passwd
grep –color root /etc/passwd
Finding a text in list of files in a directory.
Grep From Files and Display the File Name On Linux
grep -l “string” filenamegrep -l root /etc/*
use grep recursively
grep -R “192.168.0.1” /etc/
grep -R ‘string’ dir/
grep -nr ‘ssl’ .
The dot at the end searches the current directory. Meaning for each parameter:
-n Show relative line number in the file
‘yourString*’ String for search, followed by a wildcard character
-r Recursively search subdirectories listed
. Directory for search (current directory)
/etc/nginx/sites-enabled# grep -nr ‘ssl’ .
./eaadharcard.co.in.conf:8: ssl on;
./eaadharcard.co.in.conf:9: ssl_certificate /etc/nginx/ssl/eaadharcard.co.in.pem;
./eaadharcard.co.in.conf:10: ssl_certificate_key /etc/nginx/ssl/eaadharcard.co.in.key;
./employmentnewsdaily.in:5: ssl on;
/etc/nginx/sites-enabled# grep -nr ‘raazkumar.com‘ .