open.2: Some '*at' APIs have functionality that isn't in conventional APIs

Note that another reason to use the *at() APIs is to access
'flags' functionality that is not available in the corresponding
conventional APIs.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/open.2 b/man2/open.2
index 030dae67f6d6562bc6cc6d72c6454aed5c89fad7..58a38088ee595c011517eed2430ca05e80c06df5 100644 (file)
--- a/man2/open.2
+++ b/man2/open.2
@@ -1681,6 +1681,18 @@ Alternatively, such a file descriptor can be obtained by applying
 .BR dirfd (3)
 to a directory stream created using
 .BR opendir (3).
+.PP
+When these APIs are given a
+.I dirfd
+argument of
+.BR AT_FDCWD
+or the specified pathname is absolute,
+then they handle their pathname argument in the same was as
+the corresponding conventional APIs.
+However, in this case, several of the APIs have a
+.I flags
+argument that provides access to functionality that is not available with
+the corresponding conventional APIs.
 .\"
 .\"
 .SS O_DIRECT