Question

Using C on Linux, how would I go about triggering a signal handler every time I write data to a buffer using the write() function. The handler will be reading all data written to the buffer at the time of execution.

Answer 1

Sockets support this by enabling async mode on the socket file descriptor. On Linux this is done using fcntl calls:

/* set socket owner (the process that will receive signals) */
fcntl(fd, F_SETOWN, getpid());

/* optional if you want to receive a real-time signal instead of SIGIO */
fnctl(fd, F_SETSIG, signum);

/* turn on async mode -- this is the important part which enables signal delivery */
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_ASYNC);