Thomas Wouters <thomas@xs4all.net>:

This patch adds the openpty() and forkpty() library calls to posixmodule.c,
when they are available on the target
system. (glibc-2.1-based Linux systems, FreeBSD and BSDI at least, probably
the other BSD-based systems as well.)

Lib/pty.py is also rewritten to use openpty when available, but falls
back to the old SGI method or the "manual" BSD open-a-pty
code. Openpty() is necessary to use the Unix98 ptys under Linux 2.2,
or when using non-standard tty names under (at least) BSDI, which is
why I needed it, myself ;-) forkpty() is included for symmetry.

Lib/pty.py

@@ -16,9 +16,37 @@ STDERR_FILENO = 2
 
 CHILD = 0
 
+def openpty():
+	"""openpty() -> (master_fd, slave_fd)
+	Open a pty master/slave pair, using os.openpty() if possible."""
+
+	try:
+		return os.openpty()
+	except (AttributeError, OSError):
+		pass
+	master_fd, slave_name = _open_terminal()
+	slave_fd = _slave_open(slave_name)
+	return master_fd, slave_fd
+
 def master_open():
+	"""master_open() -> (master_fd, slave_name)
+	Open a pty master and return the fd, and the filename of the slave end.
+	Deprecated, use openpty() instead."""
+
+	try:
+		master_fd, slave_fd = os.openpty()
+	except (AttributeError, OSError):
+		pass
+	else:
+		slave_name = os.ttyname(slave_fd)
+		os.close(slave_fd)
+		return master_fd, slave_name
+
+	return _open_terminal()
+
+def _open_terminal():
 	"""Open pty master and return (master_fd, tty_name).
-	SGI and Linux/BSD version."""
+	SGI and generic BSD version, for when openpty() fails."""
 	try:
 		import sgi
 	except ImportError:
@@ -40,22 +68,35 @@ def master_open():
 	raise os.error, 'out of pty devices'
 
 def slave_open(tty_name):
-	"""Open the pty slave and acquire the controlling terminal.
-	Return the file descriptor.  Linux version."""
-	# (Should be universal? --Guido)
+	"""slave_open(tty_name) -> slave_fd
+	Open the pty slave and acquire the controlling terminal, returning
+	opened filedescriptor.
+	Deprecated, use openpty() instead."""
+
 	return os.open(tty_name, FCNTL.O_RDWR)
 
 def fork():
-	"""Fork and make the child a session leader with a controlling terminal.
-	Return (pid, master_fd)."""
-	master_fd, tty_name = master_open() 
+	"""fork() -> (pid, master_fd)
+	Fork and make the child a session leader with a controlling terminal."""
+
+	try:
+		pid, fd = os.forkpty()
+	except (AttributeError, OSError):
+		pass
+	else:
+		if pid == CHILD:
+			try:
+				os.setsid()
+			except OSError:
+				# os.forkpty() already set us session leader
+				pass
+		return pid, fd
+
+	master_fd, slave_fd = openpty() 
 	pid = os.fork()
 	if pid == CHILD:
 		# Establish a new session.
 		os.setsid()
-
-		# Acquire controlling terminal.
-		slave_fd = slave_open(tty_name)
 		os.close(master_fd)
 
 		# Slave becomes stdin/stdout/stderr of child.
@@ -68,17 +109,17 @@ def fork():
 	# Parent and child process.
 	return pid, master_fd
 
-def writen(fd, data):
+def _writen(fd, data):
 	"""Write all the data to a descriptor."""
 	while data != '':
 		n = os.write(fd, data)
 		data = data[n:]
 
-def read(fd):
+def _read(fd):
 	"""Default read function."""
 	return os.read(fd, 1024)
 
-def copy(master_fd, master_read=read, stdin_read=read):
+def _copy(master_fd, master_read=_read, stdin_read=_read):
 	"""Parent copy loop.
 	Copies  
 	  	pty master -> standard output	(master_read)
@@ -91,9 +132,9 @@ def copy(master_fd, master_read=read, stdin_read=read):
 			os.write(STDOUT_FILENO, data)
 		if STDIN_FILENO in rfds:
 			data = stdin_read(STDIN_FILENO)
-			writen(master_fd, data)
+			_writen(master_fd, data)
 
-def spawn(argv, master_read=read, stdin_read=read):
+def spawn(argv, master_read=_read, stdin_read=_read):
 	"""Create a spawned process."""
 	if type(argv) == type(''):
 		argv = (argv,)
@@ -103,6 +144,6 @@ def spawn(argv, master_read=read, stdin_read=read):
 	mode = tty.tcgetattr(STDIN_FILENO)
 	tty.setraw(STDIN_FILENO)
 	try:
-		copy(master_fd, master_read, stdin_read)
+		_copy(master_fd, master_read, stdin_read)
 	except:
 		tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)

Modules/posixmodule.c

@@ -1731,6 +1731,64 @@ posix_fork(self, args)
 }
 #endif
 
+#if defined(HAVE_OPENPTY) || defined(HAVE_FORKPTY)
+#ifdef HAVE_PTY_H
+#include <pty.h>
+#else
+#ifdef HAVE_LIBUTIL_H
+#include <libutil.h>
+#else
+/* BSDI does not supply a prototype for the 'openpty' and 'forkpty'
+   functions, eventhough they are included in libutil. */
+#include <termios.h>
+extern int openpty(int *, int *, char *, struct termios *, struct winsize *);
+extern int forkpty(int *, char *, struct termios *, struct winsize *);
+#endif /* HAVE_LIBUTIL_H */
+#endif /* HAVE_PTY_H */
+#endif /* defined(HAVE_OPENPTY) or defined(HAVE_FORKPTY) */
+
+#ifdef HAVE_OPENPTY
+static char posix_openpty__doc__[] =
+"openpty() -> (master_fd, slave_fd)\n\
+Open a pseudo-terminal, returning open fd's for both master and slave end.\n";
+
+static PyObject *
+posix_openpty(self, args)
+	PyObject *self;
+	PyObject *args;
+{
+	int master_fd, slave_fd;
+	if (!PyArg_ParseTuple(args, ":openpty"))
+		return NULL;
+	if (openpty(&master_fd, &slave_fd, NULL, NULL, NULL) != 0)
+		return posix_error();
+	return Py_BuildValue("(ii)", master_fd, slave_fd);
+}
+#endif
+
+#ifdef HAVE_FORKPTY
+static char posix_forkpty__doc__[] =
+"forkpty() -> (pid, master_fd)\n\
+Fork a new process with a new pseudo-terminal as controlling tty.\n\n\
+Like fork(), return 0 as pid to child process, and PID of child to parent.\n\
+To both, return fd of newly opened pseudo-terminal.\n";
+
+static PyObject *
+posix_forkpty(self, args)
+	PyObject *self;
+	PyObject *args;
+{
+	int master_fd, pid;
+	
+	if (!PyArg_ParseTuple(args, ":forkpty"))
+		return NULL;
+	pid = forkpty(&master_fd, NULL, NULL, NULL);
+	if (pid == -1)
+		return posix_error();
+	PyOS_AfterFork();
+	return Py_BuildValue("(ii)", pid, master_fd);
+}
+#endif
 
 #ifdef HAVE_GETEGID
 static char posix_getegid__doc__[] =
@@ -4514,6 +4572,12 @@ static PyMethodDef posix_methods[] = {
 #ifdef HAVE_FORK
 	{"fork",	posix_fork, METH_VARARGS, posix_fork__doc__},
 #endif /* HAVE_FORK */
+#ifdef HAVE_OPENPTY
+	{"openpty",	posix_openpty, METH_VARARGS, posix_openpty__doc__},
+#endif /* HAVE_OPENPTY */
+#ifdef HAVE_FORKPTY
+	{"forkpty",	posix_forkpty, METH_VARARGS, posix_forkpty__doc__},
+#endif /* HAVE_FORKPTY */
 #ifdef HAVE_GETEGID
 	{"getegid",	posix_getegid, METH_VARARGS, posix_getegid__doc__},
 #endif /* HAVE_GETEGID */

configure.in

@@ -357,7 +357,7 @@ AC_CHECK_HEADERS(dlfcn.h fcntl.h limits.h locale.h ncurses.h pthread.h \
 signal.h stdarg.h stddef.h stdlib.h thread.h unistd.h utime.h \
 sys/audioio.h sys/file.h sys/lock.h \
 sys/param.h sys/select.h sys/socket.h sys/time.h sys/times.h \
-sys/un.h sys/utsname.h sys/wait.h)
+sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h)
 AC_HEADER_DIRENT
 
 # checks for typedefs
@@ -771,6 +771,11 @@ AC_CHECK_FUNCS(alarm chown clock confstr ctermid ctermid_r dlopen execv \
  tcgetpgrp tcsetpgrp tempnam timegm times tmpfile tmpnam tmpnam_r \
  truncate uname waitpid)
 
+# check for openpty and forkpty
+
+AC_CHECK_FUNCS(openpty,, AC_CHECK_LIB(util,openpty, [AC_DEFINE(HAVE_OPENPTY)] [LIBS="$LIBS -lutil"]))
+AC_CHECK_FUNCS(forkpty,, AC_CHECK_LIB(util,forkpty, [AC_DEFINE(HAVE_FORKPTY)] [LIBS="$LIBS -lutil"]))
+
 # check for long file support functions
 AC_CHECK_FUNCS(fseek64 fseeko fstatvfs ftell64 ftello statvfs)