Date: Wed, 8 Jan 2020 11:42:44 +0000 From: Steve O'Hara-Smith <steve@sohara.org> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freebsd-questions@freebsd.org Subject: Re: Independence of file descriptor flags across forks (or lack thereof) Message-ID: <20200108114244.b431a9ae0170ec947e6fb7d8@sohara.org> In-Reply-To: <94417.1578474619@segfault.tristatelogic.com> References: <94417.1578474619@segfault.tristatelogic.com>
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On Wed, 08 Jan 2020 01:10:19 -0800 "Ronald F. Guilmette" <rfg@tristatelogic.com> wrote: > Quite simply, I started some development work recently with the > (apparently naive) belief that when a process forks, and its child > process get its own "independent" copy of all of the file descriptors It does - but file descriptors are just integers - see the open manpage. > that are currently open in the parent process, the child would also get > its own independent copy of the system-maintained "flags word" for each > of those inherited file descriptor copies. The fork manpage tells you that the descriptors reference the same underlying object. It is that object (the open file) which holds the "flags word". > So dear friends, I must ask you, am I delusional? Is this all just some > massive misunderstanding on my part? Yep. -- Steve O'Hara-Smith <steve@sohara.org>
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