1 files changed, 17 insertions, 0 deletions

diff --git a/lib/libc/sys/open.2 b/lib/libc/sys/open.2
index 14d8722a109de..a2de15029a05b 100644
--- a/lib/libc/sys/open.2
+++ b/lib/libc/sys/open.2
@@ -86,7 +86,9 @@ O_SHLOCK	atomically obtain a shared lock
 O_EXLOCK	atomically obtain an exclusive lock
 O_DIRECT	eliminate or reduce cache effects
 O_FSYNC		synchronous writes
+O_SYNC		synchronous writes
 O_NOFOLLOW	do not follow symlinks
+O_NOCTTY	don't assign controlling terminal
 .Ed
 .Pp
 Opening a file with
@@ -133,6 +135,11 @@ the kernel will not cache written data
 and all writes on the descriptor will not return until
 the data to be written completes.
 .Pp
+.Dv O_SYNC
+is a synonym for
+.Dv O_FSYNC
+required by POSIX.
+.Pp
 If
 .Dv O_NOFOLLOW
 is used in the mask and the target file passed to
@@ -160,6 +167,16 @@ If it cannot avoid caching the data,
 it will minimize the impact the data has on the cache.
 Use of this flag can drastically reduce performance if not used with care.
 .Pp
+.Dv O_NOCTTY
+may be used to ensure the OS does not assign this file as the
+controlling terminal when it opens a tty device.
+This is the default on
+.Fx ,
+but is present for POSIX 1003.1 compatibility.
+.Fn open 
+will not assign controlling terminals on
+.Fx .
+.Pp
 If successful,
 .Fn open
 returns a non-negative integer, termed a file descriptor.