From: Gary Wright <gwtmp01@...>
Date: 2007-12-30T07:05:15+09:00
Subject: Re: IO#write_nonblock and Errno::EAGAIN


On Dec 29, 2007, at 1:47 PM, Tony Arcieri wrote:

> How do you figure out how many bytes were actually written in the  
> event of a partial write?
>
> Looking at the description:
>
> "write_nonblock just calls write(2). It causes all errors write(2)  
> causes: EAGAIN, EINTR, etc. The result may also be smaller than  
> string.length (partial write). The caller should care such errors  
> and partial write."
>
> In the case of a partial write, write(2) returns the number of  
> bytes written (which will differ from the number of bytes  
> requested) and set errno to EAGAIN.
>
> Is there any way to silently swallow that exception and get the  
> return value from write(2)?  I'm implementing a buffered writer and  
> need to know how many bytes to remove from the internal buffer  
> because they were successfully written.


I believe you won't get a partial write *and* an exception.
You'll get one or the other. Sometimes you'll get a partial
write and then an exception on the *next* attempt
to write to the file descriptor.  This can happen, for
example, when a network connection is shutdown in the
middle of a write.

Gary Wright