tcdrain

bajen_hasse · 03-05-2003, 02:04 AM

Hi !

tcdrain() seems to have some serios problems. If I call tcdrain after a write it just hangs there forever. Any ideas?
the code:

write(fd,(char *)&x,sizeof(x));
tcdrain(fd); <--- here we hang....
write(...)
tcdrain();
write(...);
etc..

the fd is opened with:

open("/dev/ttyS1",O_RDWR|O_NOCTTY|O_NDELAY);

If I call tcflush before I start writing(and remove the tcdrains) it works better.

wapcaplet · 03-06-2003, 07:43 AM

I think you need to use flush() after doing write().

bajen_hasse · 03-06-2003, 07:46 AM

But according to the man page tcdrain should wait until all bytes are written. flush sholud discard them.

wapcaplet · 03-06-2003, 10:12 AM

I always thought flush caused the bytes to actually be written. It doesn't discard anything. (I could be wrong though... haven't done much with networking and I/O stuff)

bajen_hasse · 03-07-2003, 12:59 AM

Normally flush works like that. But according to the termios man page drain waits and flush discards. Anyway tcdrain just hangs forevever...

wapcaplet · 03-07-2003, 06:26 AM

I am afraid I don't know what to tell you then

Hopefully someone else here can shed some light.