Grep command used for search files and search pattern.

-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

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 -n ‘root’ /etc/passwd

grep –color root /etc/passwd

Finding a text in list of files in a directory.

grep -l “string” filenamegrep -l root /etc/*

grep -R “192.168.0.1” /etc/

grep -R ‘string’ dir/

root@instance-1:/etc/nginx# grep -R ‘expires’ /etc/nginx/
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/sites-enabled/rajuginne: # Directives to send expires headers and turn off 404 error logging.
/etc/nginx/sites-enabled/rajuginne: expires 24h;
/etc/nginx/conf.d/default.conf: expires 31536000s;
/etc/nginx/conf.d/default.conf: expires 3600s;
/etc/nginx/conf.d/default.conf: expires 31536000s;
/etc/nginx/conf.d/headers.conf:#add_header expires $expires;
/etc/nginx/conf.d/headers.conf:map $sent_http_content_type $expires {
/etc/nginx/conf.d/browsercaching.confg: expires 3600s;
/etc/nginx/conf.d/expires.global: expires 365d;
/etc/nginx/conf.d/global2.config: expires max;

grep -R ‘add_header’ /etc/nginx/

grep -nr ‘ssl’ .

t@instance-1:/etc/nginx# grep -nr ‘ssl’ .
./nginx.conf:38: #ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
./nginx.conf:39: #ssl_prefer_server_ciphers on;
./rocket-nginx/README.md:153:**<a name=’faq_ssl’>Will Rocket-Nginx work if my we bsite uses a SSL certificate (https) ?</a>**
./sites-enabled/f.in.conf:5:#ssl on;
./sites-enabled/ff.in.conf:6:ssl_certificate /etc/nginx/ssl/ssc.pem;
./sites-enabled/ff.in.conf:7:ssl_certificate_key /etc/nginx/ssl/ssc.key;
./sites-enabled/ffff.in:5:#listen 443 ssl http2;
./sites-enabled/.in:8:#include /etc/letsencrypt/options-ssl-nginx. conf;

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)

cd /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;

root@instance-1:~# grep . /proc/sys/net/ipv4/tcp*mem

root@instance-1:~#/etc/nginx/sites-enabled# grep -nr ‘raazkumar.com‘ .