CertSub is a command-line tool written in Bash that allows you to quickly and easily extract subdomains associated with a domain name. By providing a single domain or a list of domains in a file, CertSub makes use of the crt.sh website to perform a search and returns a list of unique subdomains sorted in alphabetical order.
To use CertSub, simply download the certsub.sh file and make it executable:
$ chmod +x certsub.sh
You can then run CertSub by providing a single domain with the -u option:
$ ./certsub.sh -u example.com
Or, you can provide a list of domains in a file with the -f option:
$ ./certsub.sh -f domains.txt
The file domains.txt should contain one domain per line.
Given a file named domains.txt with the following contents:
example.com
test.com
Run the following command:
