Search is the most important factor which we often used in our daily routine. Some time we need to search multiple words or string in a file, and grep provides the functionality to look into a file and search more than one words.

With the combination of grep command and regular expression we can search multiple words. Syntax for searching such combination is as follow:

grep 'word1\|word2\|word3' 

Below are the common examples of grep which we uses daily:

1. Search with words in any text file:

$ grep  ‘restart\|reboot\|shutdown’  /var/log/messages

2. Grep currently running processes:

$ ps aux | grep ‘httpd\|exim\|named’

3. For exact match use the –w option:

$ grep  -w ‘restart\|reboot\|shutdown’  /var/log/messages

The same can also achieved with the egrep command. Below are the examples:

$ egrep  ‘restart|reboot|shutdown’  /var/log/messages

If you findany difficulty in using this command, please let us know.