Function Explanation: check_links

The check_links function performs the following tasks:

1. Writes the header for the report, including the current date and time, to the report file.
2. Extracts all href values (links) from the HTML content of the specified URL using curl and sed.
3. Iterates over each extracted link.
4. Checks if the link is absolute or relative:
   • If the link is relative, it adds the base URL to form a complete URL.
5. Uses curl to measure the HTTP status code for each link. The curl command is used with the following options:
   • -o /dev/null: Discards the output.
   • -s: Silent mode, which suppresses progress and error messages.
   • -w "%{http_code}\n": Writes the HTTP status code to the variable.
   • -L: Follows redirects.
6. Checks if the HTTP status code is 200. If it is, it appends a message stating the link is valid to the report file. Otherwise, it appends a message stating the link is invalid, along with the HTTP status code.
7. Prints a message indicating that the report has been saved.