Bulk utility to Add "A" Entry

Copy sub-domain names in a single file (one name per line) for example, create a file /root/subdomain and add sub-domains

abc
xyz
qaz
wsx

Save the file and execute the following script

where,
xx.xx.xx.xx is the IP you want to point the sub-domains to.
yourdomain.tld is the domain on which you want to set the sub-domains.

Don't forget to restart the 'named' service.