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1"""Pseudo terminal utilities."""
2
3# Bugs: No signal handling.  Doesn't set slave termios and window size.
4#       Only tested on Linux.
5# See:  W. Richard Stevens. 1992.  Advanced Programming in the
6#       UNIX Environment.  Chapter 19.
7# Author: Steen Lumholt -- with additions by Guido.
8
9from select import select
10import os
11import tty
12
13__all__ = ["openpty","fork","spawn"]
14
15STDIN_FILENO = 0
16STDOUT_FILENO = 1
17STDERR_FILENO = 2
18
19CHILD = 0
20
21def openpty():
22    """openpty() -> (master_fd, slave_fd)
23    Open a pty master/slave pair, using os.openpty() if possible."""
24
25    try:
26        return os.openpty()
27    except (AttributeError, OSError):
28        pass
29    master_fd, slave_name = _open_terminal()
30    slave_fd = slave_open(slave_name)
31    return master_fd, slave_fd
32
33def master_open():
34    """master_open() -> (master_fd, slave_name)
35    Open a pty master and return the fd, and the filename of the slave end.
36    Deprecated, use openpty() instead."""
37
38    try:
39        master_fd, slave_fd = os.openpty()
40    except (AttributeError, OSError):
41        pass
42    else:
43        slave_name = os.ttyname(slave_fd)
44        os.close(slave_fd)
45        return master_fd, slave_name
46
47    return _open_terminal()
48
49def _open_terminal():
50    """Open pty master and return (master_fd, tty_name).
51    SGI and generic BSD version, for when openpty() fails."""
52    try:
53        import sgi
54    except ImportError:
55        pass
56    else:
57        try:
58            tty_name, master_fd = sgi._getpty(os.O_RDWR, 0666, 0)
59        except IOError, msg:
60            raise os.error, msg
61        return master_fd, tty_name
62    for x in 'pqrstuvwxyzPQRST':
63        for y in '0123456789abcdef':
64            pty_name = '/dev/pty' + x + y
65            try:
66                fd = os.open(pty_name, os.O_RDWR)
67            except os.error:
68                continue
69            return (fd, '/dev/tty' + x + y)
70    raise os.error, 'out of pty devices'
71
72def slave_open(tty_name):
73    """slave_open(tty_name) -> slave_fd
74    Open the pty slave and acquire the controlling terminal, returning
75    opened filedescriptor.
76    Deprecated, use openpty() instead."""
77
78    result = os.open(tty_name, os.O_RDWR)
79    try:
80        from fcntl import ioctl, I_PUSH
81    except ImportError:
82        return result
83    try:
84        ioctl(result, I_PUSH, "ptem")
85        ioctl(result, I_PUSH, "ldterm")
86    except IOError:
87        pass
88    return result
89
90def fork():
91    """fork() -> (pid, master_fd)
92    Fork and make the child a session leader with a controlling terminal."""
93
94    try:
95        pid, fd = os.forkpty()
96    except (AttributeError, OSError):
97        pass
98    else:
99        if pid == CHILD:
100            try:
101                os.setsid()
102            except OSError:
103                # os.forkpty() already set us session leader
104                pass
105        return pid, fd
106
107    master_fd, slave_fd = openpty()
108    pid = os.fork()
109    if pid == CHILD:
110        # Establish a new session.
111        os.setsid()
112        os.close(master_fd)
113
114        # Slave becomes stdin/stdout/stderr of child.
115        os.dup2(slave_fd, STDIN_FILENO)
116        os.dup2(slave_fd, STDOUT_FILENO)
117        os.dup2(slave_fd, STDERR_FILENO)
118        if (slave_fd > STDERR_FILENO):
119            os.close (slave_fd)
120
121        # Explicitly open the tty to make it become a controlling tty.
122        tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)
123        os.close(tmp_fd)
124    else:
125        os.close(slave_fd)
126
127    # Parent and child process.
128    return pid, master_fd
129
130def _writen(fd, data):
131    """Write all the data to a descriptor."""
132    while data != '':
133        n = os.write(fd, data)
134        data = data[n:]
135
136def _read(fd):
137    """Default read function."""
138    return os.read(fd, 1024)
139
140def _copy(master_fd, master_read=_read, stdin_read=_read):
141    """Parent copy loop.
142    Copies
143            pty master -> standard output   (master_read)
144            standard input -> pty master    (stdin_read)"""
145    fds = [master_fd, STDIN_FILENO]
146    while True:
147        rfds, wfds, xfds = select(fds, [], [])
148        if master_fd in rfds:
149            data = master_read(master_fd)
150            if not data:  # Reached EOF.
151                fds.remove(master_fd)
152            else:
153                os.write(STDOUT_FILENO, data)
154        if STDIN_FILENO in rfds:
155            data = stdin_read(STDIN_FILENO)
156            if not data:
157                fds.remove(STDIN_FILENO)
158            else:
159                _writen(master_fd, data)
160
161def spawn(argv, master_read=_read, stdin_read=_read):
162    """Create a spawned process."""
163    if type(argv) == type(''):
164        argv = (argv,)
165    pid, master_fd = fork()
166    if pid == CHILD:
167        os.execlp(argv[0], *argv)
168    try:
169        mode = tty.tcgetattr(STDIN_FILENO)
170        tty.setraw(STDIN_FILENO)
171        restore = 1
172    except tty.error:    # This is the same as termios.error
173        restore = 0
174    try:
175        _copy(master_fd, master_read, stdin_read)
176    except (IOError, OSError):
177        if restore:
178            tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)
179
180    os.close(master_fd)
181