[PATCH] chmod.2: document fchmodat(AT_EMPTY_PATH)

[PATCH] chmod.2: document fchmodat(AT_EMPTY_PATH)

[Aleksa Sarai]

The documentation and behaviour is indentical to the equivalent flag for
fchownat(2).

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
This was added back in 2023, but I forgot to send the documentation
patch for this and only noticed when I was trying to use it and realised
it wasn't in the man page -- mea culpa!
---
 man/man2/chmod.2 | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/man/man2/chmod.2 b/man/man2/chmod.2
index 307589481593..671e256ba525 100644
--- a/man/man2/chmod.2
+++ b/man/man2/chmod.2
@@ -190,7 +190,30 @@ is absolute, then
 is ignored.
 .P
 .I flags
-can either be 0, or include the following flag:
+can either be 0, or include the following flags:
+.TP
+.BR AT_EMPTY_PATH " (since Linux 6.6)"
+.\" commit 5daeb41a6fc9d0d81cb2291884b7410e062d8fa1
+If
+.I path
+is an empty string, operate on the file referred to by
+.I dirfd
+(which may have been obtained using the
+.BR open (2)
+.B O_PATH
+flag).
+In this case,
+.I dirfd
+can refer to any type of file, not just a directory.
+If
+.I dirfd
+is
+.BR AT_FDCWD ,
+the call operates on the current working directory.
+This flag is Linux-specific; define
+.B _GNU_SOURCE
+.\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
+to obtain its definition.
 .TP
 .B AT_SYMLINK_NOFOLLOW
 If

---
base-commit: 471c38fb3c5c53c6df2fad4a7353559b330c1323
change-id: 20250619-fchmod-empty-path-7680e8bb5481

Best regards,
-- 
Aleksa Sarai <cyphar@cyphar.com>

Re: [PATCH] chmod.2: document fchmodat(AT_EMPTY_PATH)

[Alejandro Colomar]

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Hi Aleksa,

On Thu, Jun 19, 2025 at 04:34:30AM +1000, Aleksa Sarai wrote:
> The documentation and behaviour is indentical to the equivalent flag for
> fchownat(2).
> 
> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
> ---
> This was added back in 2023, but I forgot to send the documentation
> patch for this and only noticed when I was trying to use it and realised
> it wasn't in the man page -- mea culpa!

Thanks!  I've applied the patch:
<https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=a4535bb6ddc0c1a060cedaee86430c39f590804e>

Have a lovely day!
Alex

> ---
>  man/man2/chmod.2 | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/man/man2/chmod.2 b/man/man2/chmod.2
> index 307589481593..671e256ba525 100644
> --- a/man/man2/chmod.2
> +++ b/man/man2/chmod.2
> @@ -190,7 +190,30 @@ is absolute, then
>  is ignored.
>  .P
>  .I flags
> -can either be 0, or include the following flag:
> +can either be 0, or include the following flags:
> +.TP
> +.BR AT_EMPTY_PATH " (since Linux 6.6)"
> +.\" commit 5daeb41a6fc9d0d81cb2291884b7410e062d8fa1
> +If
> +.I path
> +is an empty string, operate on the file referred to by
> +.I dirfd
> +(which may have been obtained using the
> +.BR open (2)
> +.B O_PATH
> +flag).
> +In this case,
> +.I dirfd
> +can refer to any type of file, not just a directory.
> +If
> +.I dirfd
> +is
> +.BR AT_FDCWD ,
> +the call operates on the current working directory.
> +This flag is Linux-specific; define
> +.B _GNU_SOURCE
> +.\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
> +to obtain its definition.
>  .TP
>  .B AT_SYMLINK_NOFOLLOW
>  If
> 
> ---
> base-commit: 471c38fb3c5c53c6df2fad4a7353559b330c1323
> change-id: 20250619-fchmod-empty-path-7680e8bb5481
> 
> Best regards,
> -- 
> Aleksa Sarai <cyphar@cyphar.com>
> 
> 

-- 
<https://www.alejandro-colomar.es/>

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