March 2, 2019
6:45 p.m.
On Fri, 01 Mar 2019 23:29:53 -0500, Jeffrey Walton said:
I cannot seem to open the device in exclusive mode. The current open is (I also tried with O_EXCL):
int modem = open(device_path, O_RDWR | O_NOCTTY | O_SYNC);
So what happens? Does the open fail? If so, what does perror() say about it? Or does the open work but the flag is ignored? Have you tried making the *other* program open it with O_EXCL so your caller-id program can't mess with its state?