Question

Could the socket function call in C return 0 or 1 as the value for the socket descriptor?

   int socket(int domain, int type, int protocol);

According to the man page I have:

RETURN VALUE
   -1 is returned if an error occurs; otherwise the  return  value  is  a
   descriptor referencing the socket.

It seems like it could, or at least the man page makes no mention of any reserved values. Is it written somewhere else that valid socket descriptors need to be 2 or greater?

I’m specifically running on a linux 2.4.22 kernel, but I’m curious to know for any unix based implementation of socket.

Answer 1

Both 0 and 1 are valid return vales, and might indeed be returned if the application has closed its standard input or output file descriptors.