Rtems telnetd/shell question (and Why does fgetc() return 0 for a 0-length socket read?)

Chris Johns chrisj at rtems.org
Fri Oct 30 03:16:19 UTC 2009

Peter Dufault wrote:
> On Oct 28, 2009, at 6:11 , Chris Johns wrote:
>> I suspect we need to handle a read of the fd better. Closing a remote 
>> end of a socket always returns a length of 0. I do not know how this 
>> is handled with fget.
> I'm just sitting down to look a this, and the first thing I'm asking is 
> how can fgetc() return 0 when the socket it is buffering returns a 0 
> length read?  Since 0 is a valid return for fgetc() this doesn't make 
> any sense.  I don't have too much time to write test programs right now 
> so I'm throwing out this question: can fgetc() return 0 for a zero 
> length read on an underlying socket, or is there a new lower-level bug 
> that is screwing things up?
> The fgetc() man page isn't clear and I didn't come up with an internet 
> search to get the answer.

We could always remove the fgetc call and use read but the user command 
handlers could have the same problem if they read from stdin.

I am wondering if this is a bug in newlib and should be fixed.


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