From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rick Jones <rick.jones2@hp.com>
Subject: Re: write() udp socket
Date: Mon, 25 Jul 2011 10:38:12 -0700
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Cc: ZHOU Xiaobo <xb.zhou@qq.com>, netdev <netdev@vger.kernel.org>
To: Huajun Li <huajun.li.lee@gmail.com>
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On 07/24/2011 01:33 AM, Huajun Li wrote:
> 2011/7/23 ZHOU Xiaobo<xb.zhou@qq.com>:
>> question No1:
>> When I call
>> ssize_t write(int fd, const void *buf, size_t count);
>>
>>
>> on a nonblocking UDP socket, is the return value  always equal to 'count'?
>>
>>
>
> I don't think so.  The function may be interrupt by signal or return
> due to other reason, so the return value only represents the size it
> writes successfully to the fd.

I believe it should either appaear to succeed or fail.  write() best not 
be sending partial UDP datagrams.  That would be "bad."