Describe open(2) exported constants
diff --git a/Doc/lib/libposix.tex b/Doc/lib/libposix.tex
index a0fccdd..4870c4f 100644
--- a/Doc/lib/libposix.tex
+++ b/Doc/lib/libposix.tex
@@ -431,3 +431,33 @@
The option for \code{waitpid()} to avoid hanging if no child process
status is available immediately.
\end{datadesc}
+
+
+\begin{datadesc}{O_RDONLY}
+\end{datadesc}
+\begin{datadesc}{O_WRONLY}
+\end{datadesc}
+\begin{datadesc}{O_RDWR}
+\end{datadesc}
+\begin{datadesc}{O_NDELAY}
+\end{datadesc}
+\begin{datadesc}{O_NONBLOCK}
+\end{datadesc}
+\begin{datadesc}{O_APPEND}
+\end{datadesc}
+\begin{datadesc}{O_DSYNC}
+\end{datadesc}
+\begin{datadesc}{O_RSYNC}
+\end{datadesc}
+\begin{datadesc}{O_SYNC}
+\end{datadesc}
+\begin{datadesc}{O_NOCTTY}
+\end{datadesc}
+\begin{datadesc}{O_CREAT}
+\end{datadesc}
+\begin{datadesc}{O_EXCL}
+\end{datadesc}
+\begin{datadesc}{O_TRUNC}
+Options for the \code{flag} argument to the \code{open()} function.
+These can be bit-wise OR'd together.
+\end{datadesc}