Hello Tim,
On 09/02/2016 09:37 AM, Tim Savannah wrote:
> Hey,
>
> There's a mistake/typo in RENAME(2) [man chapter 2, rename function]
>
> In description it says:
>
> " If newpath already exists, it will be atomically replaced (subject
> to a few conditions; see ERRORS below), so that there is no point at
> which another process
> attempting to access newpath will find it missing.
> "
>
> The "see ERRORS below" should actually read "see BUGS below".
>
>
> The "ERRORS" lists the various values of errno for various error conditions.
>
> The "BUGS" section actually describes the conditions being referred-to in
> the description:
>
> """
> BUGS
> On NFS filesystems, you can not assume that if the operation failed,
> the file was not renamed. If the server does the rename operation and
> then crashes, the
> retransmitted RPC which will be processed when the server is up
> again causes a failure. The application is expected to deal with this.
> See link(2) for a similar
> problem.
> """
I think the sentence you cite is problematic, but for different reasons
than you suggest. The wording suggests that there are ERRORS that may
cause the operation to be nonatomic. The point is of course that there
are various restrictions on rename operations that may cause the operation
to fail. I reworded the opening paragraphs prevent that misinterpretation:
rename() renames a file, moving it between directories if
required. Any other hard links to the file (as created using
link(2)) are unaffected. Open file descriptors for oldpath are
also unaffected.
# Various restrictions determine whether or not the rename operation
# succeeds: see ERRORS below.
If newpath already exists, it will be atomically replaced (##), so that
there is no point at which another process attempting to access
newpath will find it missing.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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