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Diffstat (limited to 'lib/libsys/write.2')
| -rw-r--r-- | lib/libsys/write.2 | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/libsys/write.2 b/lib/libsys/write.2 index d2ff41ceead9..77067893ab4c 100644 --- a/lib/libsys/write.2 +++ b/lib/libsys/write.2 @@ -132,6 +132,26 @@ and may write fewer bytes than requested; the return value must be noted, and the remainder of the operation should be retried when possible. +.Sh ATOMICITY OF WRITES +When operating on regular files on local file systems, the effects of +.Fn write +are atomic. +As required by the POSIX standard, +the +.Fn read , +.Fn write , +and +.Fn ftruncate +functions and their variations are atomic with respect to +each other on the file data and metadata for regular files. +See for instance +.St -p1003.1-2024 +Volume 2, Section 2.9.7 for more information. +.Pp +.Fx +implements the requirement by taking +a read/write range lock on the file byte range +affected by the corresponding function. .Sh RETURN VALUES Upon successful completion the number of bytes which were written is returned. |