GREP trips and tips

Search for a string in a file

$ grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash

case insensitive

$ grep -i ROOT /etc/passwd
root:x:0:0:root:/root:/bin/bash

wrap search string around quotes

$ grep -i "gnats bug" /etc/passwd
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin

line number

$ grep -n root /etc/passwd
1:root:x:0:0:root:/root:/bin/bash

recursive search

$ grep -r "mydomain.com" /etc/nginx/
/etc/nginx/sites-available/mydomain.com.vhost:        if ($http_host != "www.mydomain.com") {

multiple matches

$ egrep "root|news" /etc/passwd
root:x:0:0:root:/root:/bin/bash
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin

inverted matches (filter out)

$ grep -v root /etc/passwd
prints everything except for lines with root