[PATCH 1/1] fcntl: F_GETFL: return value contains additional internal flags

[PATCH 1/1] fcntl: F_GETFL: return value contains additional internal flags

[Heinrich Schuchardt]

flags = fcntl(fd, F_GETFL);

can return more flags than those defined in the open(2) manpage, e.g.
  #define FMODE_NONOTIFY 0x1000000

The manpage should point this out.

Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
---
 man2/fcntl.2 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/man2/fcntl.2 b/man2/fcntl.2
index fc1d3b3..0fd2d0a 100644
--- a/man2/fcntl.2
+++ b/man2/fcntl.2
@@ -180,6 +180,9 @@ The file status flags and their semantics are described in
 Get the file access mode and the file status flags;
 .I arg
 is ignored.
+The return value contains the file status flags as described in
+.IR open (2).
+It may additionally contain status flags that are only used internally.
 .TP
 .BR F_SETFL " (\fIint\fP)"
 Set the file status flags to the value specified by
-- 
1.9.2

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Re: [PATCH 1/1] fcntl: F_GETFL: return value contains additional internal flags

[Michael Kerrisk (man-pages)]

Hi Heinrich,

On Thu, Apr 24, 2014 at 10:05 PM, Heinrich Schuchardt
<xypron.glpk-Mmb7MZpHnFY@public.gmane.org> wrote:
> flags = fcntl(fd, F_GETFL);
>
> can return more flags than those defined in the open(2) manpage, e.g.
>   #define FMODE_NONOTIFY 0x1000000
>
> The manpage should point this out.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>

I think it might be good to mention a concrete example here. So, how
about explicitly mentioning the FMODE_NONOTIFY and the fanotify(7) man
page. Could you redraft?

Thanks,

Michael


> ---
>  man2/fcntl.2 | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/man2/fcntl.2 b/man2/fcntl.2
> index fc1d3b3..0fd2d0a 100644
> --- a/man2/fcntl.2
> +++ b/man2/fcntl.2
> @@ -180,6 +180,9 @@ The file status flags and their semantics are described in
>  Get the file access mode and the file status flags;
>  .I arg
>  is ignored.
> +The return value contains the file status flags as described in
> +.IR open (2).
> +It may additionally contain status flags that are only used internally.
>  .TP
>  .BR F_SETFL " (\fIint\fP)"
>  Set the file status flags to the value specified by
> --
> 1.9.2
>



-- 
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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Re: [PATCH 1/1] fcntl: F_GETFL: return value contains additional internal flags

[Heinrich Schuchardt]

On 25.04.2014 15:46, Michael Kerrisk (man-pages) wrote:
> Hi Heinrich,
>
> On Thu, Apr 24, 2014 at 10:05 PM, Heinrich Schuchardt
> <xypron.glpk-Mmb7MZpHnFY@public.gmane.org> wrote:
>> flags = fcntl(fd, F_GETFL);
>>
>> can return more flags than those defined in the open(2) manpage, e.g.
>>    #define FMODE_NONOTIFY 0x1000000
>>
>> The manpage should point this out.
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
>
> I think it might be good to mention a concrete example here. So, how
> about explicitly mentioning the FMODE_NONOTIFY and the fanotify(7) man
> page. Could you redraft?

Please, read my mail
Re: fanotify API: FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME
13.04.2014 16:05 (CEST)
http://www.spinics.net/lists/linux-man/msg05366.html

I mentioned that some other flags can be returned by fcntl, too. These 
are not specific to fanotify. The examples given were

0x20 (FMODE_EXEC), and
0x800 (FMODE_NOCMTIME)

All relevant flags are defined in
include/uapi/asm-generic/fcntl.h

So would it not make more sense to relate to this include instead of 
fanotify(7)?

I never got a reply to the question asked in aforementioned mail, 
whether the observed behavior should be mentioned in the BUGS section of 
fanotify(7).

Cheers

Heinrich

> Thanks,
>
> Michael
>
>
>> ---
>>   man2/fcntl.2 | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/man2/fcntl.2 b/man2/fcntl.2
>> index fc1d3b3..0fd2d0a 100644
>> --- a/man2/fcntl.2
>> +++ b/man2/fcntl.2
>> @@ -180,6 +180,9 @@ The file status flags and their semantics are described in
>>   Get the file access mode and the file status flags;
>>   .I arg
>>   is ignored.
>> +The return value contains the file status flags as described in
>> +.IR open (2).
>> +It may additionally contain status flags that are only used internally.
>>   .TP
>>   .BR F_SETFL " (\fIint\fP)"
>>   Set the file status flags to the value specified by
>> --
>> 1.9.2
>>
>
>
>

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