Looking at the source code, specifically src/tool_operate.c:1490, it seems like this is used for SCP/SFTP protocol support. As far as I can tell, curl reads known_hosts so it doesn’t bother you when accessing known hosts via those protocols. But don’t take my word for it, the source code is public and that’s amazing!
Well, yes. The point that I’m making is that the URL is provided in the example, and can be trivially introspected to see that it’s an https:// not an scp / sftp URL. This would mean that setting SSH_KNOWNHOSTS is silly. Perhaps this is a “bug,” and it shouldn’t do this. Perhaps there’s some fun thing that requires this, even though I can see no legitimate reason for it… Free idea if you wanna get code into libcurl, I guess…
Also something I found out about recently, was the ability to quickly turn a curl command into a native executable via the –libcurl flag and a generated C file, see https://austingwalters.com/export-a-command-line-curl-command-to-an-executable for an example.
This is neat, but why does it need:
curl_easy_setopt(hnd, CURLOPT_SSH_KNOWNHOSTS, "/home/austin/.ssh/known_hosts");? That seems odd.If you build curl with libssh2, it works with SFTP!
Why the static home dir.. who knows.
Looking at the source code, specifically
src/tool_operate.c:1490, it seems like this is used for SCP/SFTP protocol support. As far as I can tell, curl reads known_hosts so it doesn’t bother you when accessing known hosts via those protocols. But don’t take my word for it, the source code is public and that’s amazing!Well, yes. The point that I’m making is that the URL is provided in the example, and can be trivially introspected to see that it’s an
https://not an scp / sftp URL. This would mean that settingSSH_KNOWNHOSTSis silly. Perhaps this is a “bug,” and it shouldn’t do this. Perhaps there’s some fun thing that requires this, even though I can see no legitimate reason for it… Free idea if you wanna get code into libcurl, I guess…The “exercises” format used here works quite well for self-studying – does anyone know of similar articles?
Oh, boy, you’re in for a treat. This is a comprehensive overview of the general concept with lots of references: https://www.gwern.net/Spaced-repetition