diff --git a/man3/ptsname.3 b/man3/ptsname.3
index 97d743f6f..6c0db8d41 100644
--- a/man3/ptsname.3
+++ b/man3/ptsname.3
@@ -1,9 +1,11 @@
 .\" Hey Emacs! This file is -*- nroff -*- source.
 .\" This page is in the public domain. - aeb
 .\"
-.TH PTSNAME 3 "2003-01-30" "PTY Control" "Linux Programmer's Manual"
+.\" 2004-12-17, mtk, added description of ptsname_r() + ERRORS
+.\"
+.TH PTSNAME 3 "2004-12-17" "PTY Control" "Linux Programmer's Manual"
 .SH NAME
-ptsname \- get the name of the slave pseudotty
+ptsname, ptsname_r \- get the name of the slave pseudotty
 .SH SYNOPSIS
 .nf
 .B #define _XOPEN_SOURCE
@@ -11,26 +13,78 @@ ptsname \- get the name of the slave pseudotty
 .B #include <stdlib.h>
 .sp
 .BI "char *ptsname(int " fd ");"
+.sp
+.B #define _GNU_SOURCE
+.br
+.B #include <stdlib.h>
+.sp
+.BI "char *ptsname_r(int " fd ", char * " buf ", size_t " buflen ");"
 .fi
 .SH DESCRIPTION
 The
 .BR ptsname ()
-function returns the name of the slave pseudo-terminal device (pty)
-corresponding to the master pty referred to by
+function returns the name of the slave pseudo-terminal (pty) device
+corresponding to the master referred to by
 .IR fd .
+
+The
+.BR ptsname_r ()
+function is the reentrant equivalent of
+.BR ptsname ().
+It returns the name of the slave pseudo-terminal device as a
+null-terminated string in the buffer pointed to by
+.IR buf .
+The
+.I buflen
+argument specifies the number of bytes available in
+.IR buf .
 .SH "RETURN VALUE"
-When successful,
+On success,
 .BR ptsname ()
-returns a pointer to a string in static storage. This pointer
-must not be freed.
-.PP
-Upon failure, 
-.BR ptsname ()
-returns a NULL pointer.
+returns a pointer to a string in static storage which will be
+overwritten by subsequent calls.
+This pointer must not be freed.
+On failure, a NULL pointer is returned.
+
+On success,
+.BR ptsname_r ()
+returns 0.
+On failure, a non-zero value is returned
+and
+.I errno
+is set to indicate the error.
+.\" In fact the errno value is also returned as the function
+.\" result -- MTK, Dec 04
+.SH ERRORS
+.TP
+.B EINVAL
+.RB ( ptsname_r ()
+only)
+.I buf
+is NULL.
+.TP
+.B ENOTTY
+.I fd
+does not refer to a pseudo-terminal master device.
+.TP
+.B ERANGE
+.RB ( ptsname_r ()
+only)
+.I buf
+is too small.
 .SH "CONFORMING TO"
-POSIX 1003.1-2001.
-This is part of the Unix98 pty support, see
-.BR pts (4).
+.BR ptsname ()
+is part of the Unix98 pseudo-terminal support (see
+.BR pts (4)).
+This function is specified in POSIX 1003.1-2001.
+
+.BR pstname_r ()
+is a Linux extension.
+A version of this function is provided on Tru64 and HP-UX, but
+on those implementations, -1 is returned on error, with
+.I errno
+set to indicate the error.
+Avoid using this function in portable programs.
 .SH "SEE ALSO"
 .BR grantpt (3),
 .BR ttyname (3),