Nonblocking IO (ITI8510)
|Real-Time Operating Systems and Systems Programming|
|[ @ ]|
Practice with nonblocking IO.
1. Canonical mode
Goal: To write a program which echoes characters on screen while typed until button 'q' is pressed. Then it quits and prints a newline.
- Try to put the terminal into noncanonical mode and remove terminal echo See 'man termios' or Google "noncanonical mode" for that.
- Note that you should restore the terminal mode before quitting since otherwise the terminal might get messed up (no echo).
- Working with bits:
flags &= ~NEWFLAG // Clears the bit NEWFLAG on flags flags |= NEWFLAG // Set the bit NEWFLAG on flags flags ^= NEWFLAG // Toggle NEWLAG
2. Nonblocking reads from a FIFO
Goal: To write a program which prints a '.' character every half-a second unless some input is provided on a fifo file.
- Use open() with O_NONBLOCK flag.
- If read() does not have anything to read, it returns with -1 and sets errno to constant EAGAIN - you can check that or try messing around with select() function.
- FIFO can be made with a 'mkfifo fifoname' command and written to using 'cat > fifoname'.
- You have to open fifo before reading (open two terminal windows).
- Write your output with write() function to bypass buffering.
- Function usleep() can be used for half-a second pause here.