How to check if there's something to read.

[andy.lo]

Hello Everyone,

I am a complete newbie to C, and I have been trying to do some serial programming.

I opened a serial port in linux using:
int fd = open ("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK );

I understand that to read the port I need to do this:
read(fd, buffer, num_char);

However my question is, is there a way to know if there is something to read from "fd" before calling read()? I tried pread(), but it just returns -1 on the serial port (maybe it is not seekable?).

Thanks in advance,

Andy


(Please bear with me, I probably don't know what I am talking about...)

[cwr]

A common way is to use either the select() or poll() functions.

You could also set the fd to nonblocking using fcntl, but this is probably a bad idea.