Linux Commands Help: grep

Find text in a file:

 For example to find out "404" requests( page not found ) in apache log file:

grep "404" /var/log/apache2/access.log

 The above command displays all the entries contains the word "404".

   

grep -n "404" /var/log/apache2/access.log

The above command displays all the entries contains the word "404" with line numbers.

   

grep -c "404" /var/log/apache2/access.log

The above command displays the no. of entries contains the word "404"

grep -c "404\|192.168.20.32" /var/log/apache2/access.log

The above command displays the no. of entries contains both the words "404" and "192.168.20.32"