Date: Tue, 15 Jun 2021 19:43:47 -0400 From: Paul Procacci <pprocacci@gmail.com> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Is a successful call to write(2) atomic? Message-ID: <CAFbbPugCir436Z6cHyOZBtRAQ0on0eFfYc0Z0xNrhHCRW3r=4A@mail.gmail.com> In-Reply-To: <25766.1623793238@segfault.tristatelogic.com> References: <CADqw_gKYTV-tRKxPFD1q78_gnpR2DWwmkTxLZJFmo4CUGqGqsg@mail.gmail.com> <25766.1623793238@segfault.tristatelogic.com>
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> I frankly don't know. It seems highly likely to me that Posix is most > probably very precise in defining the behavior, but one would have to > wade through a hundred pages or so to find the exact and crisp answer.-- > > I read some of them last night before responding to you to ensure all my ducks were in a row. ;) https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_05_01 https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_07 https://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html The last link in particular ... used to read as: "This volume of POSIX.1-2008 does not specify behavior of concurrent writes to a file from multiple processes. Applications should use some form of concurrency control. " It now reads: This volume of POSIX.1-2017 does not specify the behavior of concurrent writes to a regular file from multiple threads, except that each write is atomic (see *Thread Interactions with Regular File Operations* <https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_07>). Applications should use some form of concurrency control. In both cases, it states: "Applications should use some form of concurrency control". ~Paul __________________ :(){ :|:& };:
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