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clinuxwindowslinux-kernelposix-select

same fd can be used in select for read and write

I wish to use the same socket fd for both read and write operations. Lets say the "fd" is the one which I am working on then in that case

FD_SET(fd, &readfd);  
FD_SET(fd,&writefd);

select(fd+1, &readfd, &writefd, 0,200):

will hold good or it will return me the error.

I think since writefd and readfd are different sets the same fd can be set in both the sets. Please correct me if I am wrong.

Can I do the same behavior in poll POLLIN and POLLOUT to same fd.

Solution

  • This is ok, and the proper way to monitor the same fd for both reading and writing. The last argument to select is a struct timeval though, not an integer.