update zone file via script

Hi There, I need to add below line in zone files of dns-only server via script domain.com. 14400 IN TXT "v=spf1 ip4:xx.xx.xx.0/24 ip4:yy.yy.yy.0/24 a:mail.domain.com -all" where domain.com is a variable. Kindly help to add it via script as it is for 100s zonefiles. Regards,