Assume that, you want to find and replace a specific word in a file can use sed command,

For example i would like to changed sample.com. instead of mail.sample.com

Displaying output only, without string update



sed   s/mail.sample.com/sample.com./g   /var/named/domain.com.db

To update the string,

-i is replaces the word
sed   -i    s/mail.sample.com/sample.com./g      /var/named/domain.com.db

A hole line you want to find and replace
 sed   -i    's/ns1.sample.com.  14400  IN  A  192.168.0.100/ns2.sample.com  7200  IN  A  192.168.0.1/g'   /var/named/*.*.db

Can be update all files under the directory of /var/named/


sed   -i    's/ns1.sample.com.  14400  IN  A  192.168.0.100/ns2.sample.com  7200  IN  A  192.168.0.1/g'   /var/named/*