I just started using ThingSpeak and the API library found on GIthub. The library has functions to determine if READs occurred without error, but I don't see one that returns the success/failure of a WRITE.
I just started using ThingSpeak and the API library found on GIthub.
Github is a huge place. Since you have already tracked down some mysterious library, post a link to it. Waving your arms in some vague direction is useless.
Not sure about your particular library but the HTTP request to add a value returns a 200 status code and a positive integer in the payload when it successfully completes. The integer returned is the sequence number of the point just written so successive writes return 1,2,3,4 etc.