How to know when a process executed by sshpass finishes

[okashany]

I'm currently using fork and execvpe in order to run the following command:
"sshpass -e scp -v -y ".

Is there a way to know when scp finishes to transfer the file?
When I'm using waitpid, I believe it waits for sshpass to complete and
does not indicate the completion of the transfer.

Thanks!