a filename when none exists
One of the most commonly used curl command line options is the dash capital O (-O) which also is known as dash dash remote-name (--remote-name) in its long form.
This option tells curl to create a local file using the name from the filename part of the provided URL when downloading. I.e. when you tell curl
The -O option has been supported with this functionality since curl first shipped, in March 1998. An important point here is that it picks the name from the URL so that a user can tell what filename it creates. No surprises. The remote server is not involved in naming it.
Since there are no filename parts in these URLs, they used to cause curl to refuse to operate with -O and instead return error. curl could not create a local filename to use:
Starting in curl 8.10.0, curl works a little harder to come up with a filename to store the download in when -O is used. While there is no filename part in the URL, the user did ask curl to download the URL to a local file so it now tries a few extra steps:
