UNIX for Dummies Questions & Answers

hi everybody;
trying to c unix programming and ive stucked with a problem:
simple program
filedr=open("tempfile",O_RDWR|O_TRUNC,0);
write(filedr,msg1,6);
int i;
i=read(filedr,msg3,4);

it returns 0 bytes read ... why?
well if i try to poll() before read , it doesnt indicate POLLHUP or something.......

You have to reposition the file descriptor in your file to the start of the file before the read command:

Code:

lseek (filedr, 0, SEEK_SET)

Regards

Yeah.Right...But what & why poll() tells me that after write() executes POLLHUP.?

does it have to tell me that? if read returns 0 that maybe a eof.....

i cant get how does poll() OR select() works..(
ive tried to do 2 processes with 1 desrciptor.one process is mad - writing infititevly.another one checking the descriptor on read and write....and it always tell me that the second process can do the mentioned work.is that something like OS does block one after the second process is tring to do smth and give him control?