added WNOHANG
diff --git a/Doc/lib/libposix.tex b/Doc/lib/libposix.tex
index ae041c4..fa0b42d 100644
--- a/Doc/lib/libposix.tex
+++ b/Doc/lib/libposix.tex
@@ -52,7 +52,7 @@
\code{perror()}.
\end{excdesc}
-It defines the following functions:
+It defines the following functions and constants:
\renewcommand{\indexsubitem}{(in module posix)}
\begin{funcdesc}{chdir}{path}
@@ -355,3 +355,8 @@
\code{posix.fdopen}, or \code{sys.stdout} or \code{sys.stderr}, use
its \code{write()} method.
\end{funcdesc}
+
+\begin{datadesc}{WNOHANG}
+The option for \code{waitpid()} to avoid hanging if no child process
+status is available immediately.
+\end{datadesc}