[glibc] manual: add dup3

[glibc] manual: add dup3

[DJ Delorie]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a07e000e82cb71238259e674529c37c12dc7d423

commit a07e000e82cb71238259e674529c37c12dc7d423
Author: DJ Delorie <dj@redhat.com>
Date:   Fri May 10 17:34:29 2024 -0400

    manual: add dup3
    
    Reviewed-by: Florian Weimer <fweimer@redhat.com>

Diff:
---
 manual/llio.texi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/manual/llio.texi b/manual/llio.texi
index fae49d1433..fe1807a849 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -3415,6 +3415,14 @@ middle of calling @code{dup2} at which @var{new} is closed and not yet a
 duplicate of @var{old}.
 @end deftypefun
 
+@deftypefun int dup3 (int @var{old}, int @var{new}, int @var{flags})
+@standards{Linux, unistd.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+This function is the same as @code{dup2} but creates the new
+descriptor as if it had been opened with flags @var{flags}.  The only
+allowed flag is @code{O_CLOEXEC}.
+@end deftypefun
+
 @deftypevr Macro int F_DUPFD
 @standards{POSIX.1, fcntl.h}
 This macro is used as the @var{command} argument to @code{fcntl}, to