l-september.org> 527634f8   
   From: troplin@bluewin.ch   
      
   "James K. Lowden"  wrote:   
   > On Thu,  8 May 2014 06:39:57 CST   
   > Seungbeom Kim  wrote:   
   >   
   >>> Those states are as specific as I can imagine without getting into   
   >>> details from the OS.  It deals cleanly with with the EOF ambiguity   
   >>> of read(2) and, unlike stdio, distinguishes between recoverable and   
   >>> nonrecoverable errors.   
   >>   
   >> Can you please explain what is the EOF ambiguity of read(2)?   
   >   
   > When read(2) returns zero bytes, it may mean that no data   
   > were pending on a socket with nonblocking I/O, or EOF.   
   >   
   > Granted, files aren't sockets, and the standard library doesn't   
   > implement network I/O for iostreams.   But, as you know, just as a   
   > stream is not a socket, neither is it a file.  It strikes me as   
   > prescient that EOF and "no data read" are distinct.   
      
   AFAIK read/recv only return 0 on EOF. If no data is pending for nonblocking   
   IO, it returns -1 with errno set to EWOULDBLOCK or EAGAIN.   
      
   Tobi   
      
      
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