Triggering Signal Handler For I/O

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. 开发者_高级运维 The handler will be reading all data written to the buffer at the time of execution.

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);

Use pipe() with O_ASYNC and you'll recieve a SIGIO on the read end of the pipe whenever there's new data on the pipe.

I don't 100% understand what you are trying to do, BUT select might be what you need. waiting for data to be written to a file/pipe. You can use it to do/simulate asynchronous I/O.

If the file descriptor being used with write() is not for a FIFO, pipe (as suggested by Ken Bloom), asynchronous socket (as suggested by mark4o), and does not otherwise cause a signal (i.e. SIGIO), I suppose you could use raise() to send a signal to the current process after writing data to the buffer. Depending on what you are actually trying to achieve, this may not be the best solution.

Update

If I understand you correctly, you want to write to a file, have a SIGIO signal generated on completion of the write, and then read the data back from within the signal handler. It seems you want to use asynchronous I/O for a file.

In Asynchronous I/O on linux or: Welcome to hell, the author describes various asynchronous I/O techniques on Linux, including using the SIGIO signal. The SIGIO signal technique cannot be used with regular files.

Even though the author of the previously mentioned article doesn't think highly of the POSIX AIO API provided in the 2.6 kernel, you may want to look into it anyway as it can be used to provide notification of asychronous read/write completion to a regular file through signals and function callbacks.

In Boost application performance using asynchronous I/O, the author provides an overview of basic Linux I/O models before introducing the AIO API.