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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 sys
12import tty
13
14__all__ = ["openpty","fork","spawn"]
15
16STDIN_FILENO = 0
17STDOUT_FILENO = 1
18STDERR_FILENO = 2
19
20CHILD = 0
21
22def openpty():
23    """openpty() -> (master_fd, slave_fd)
24    Open a pty master/slave pair, using os.openpty() if possible."""
25
26    try:
27        return os.openpty()
28    except (AttributeError, OSError):
29        pass
30    master_fd, slave_name = _open_terminal()
31    slave_fd = slave_open(slave_name)
32    return master_fd, slave_fd
33
34def master_open():
35    """master_open() -> (master_fd, slave_name)
36    Open a pty master and return the fd, and the filename of the slave end.
37    Deprecated, use openpty() instead."""
38
39    try:
40        master_fd, slave_fd = os.openpty()
41    except (AttributeError, OSError):
42        pass
43    else:
44        slave_name = os.ttyname(slave_fd)
45        os.close(slave_fd)
46        return master_fd, slave_name
47
48    return _open_terminal()
49
50def _open_terminal():
51    """Open pty master and return (master_fd, tty_name)."""
52    for x in 'pqrstuvwxyzPQRST':
53        for y in '0123456789abcdef':
54            pty_name = '/dev/pty' + x + y
55            try:
56                fd = os.open(pty_name, os.O_RDWR)
57            except OSError:
58                continue
59            return (fd, '/dev/tty' + x + y)
60    raise OSError('out of pty devices')
61
62def slave_open(tty_name):
63    """slave_open(tty_name) -> slave_fd
64    Open the pty slave and acquire the controlling terminal, returning
65    opened filedescriptor.
66    Deprecated, use openpty() instead."""
67
68    result = os.open(tty_name, os.O_RDWR)
69    try:
70        from fcntl import ioctl, I_PUSH
71    except ImportError:
72        return result
73    try:
74        ioctl(result, I_PUSH, "ptem")
75        ioctl(result, I_PUSH, "ldterm")
76    except OSError:
77        pass
78    return result
79
80def fork():
81    """fork() -> (pid, master_fd)
82    Fork and make the child a session leader with a controlling terminal."""
83
84    try:
85        pid, fd = os.forkpty()
86    except (AttributeError, OSError):
87        pass
88    else:
89        if pid == CHILD:
90            try:
91                os.setsid()
92            except OSError:
93                # os.forkpty() already set us session leader
94                pass
95        return pid, fd
96
97    master_fd, slave_fd = openpty()
98    pid = os.fork()
99    if pid == CHILD:
100        # Establish a new session.
101        os.setsid()
102        os.close(master_fd)
103
104        # Slave becomes stdin/stdout/stderr of child.
105        os.dup2(slave_fd, STDIN_FILENO)
106        os.dup2(slave_fd, STDOUT_FILENO)
107        os.dup2(slave_fd, STDERR_FILENO)
108        if (slave_fd > STDERR_FILENO):
109            os.close (slave_fd)
110
111        # Explicitly open the tty to make it become a controlling tty.
112        tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)
113        os.close(tmp_fd)
114    else:
115        os.close(slave_fd)
116
117    # Parent and child process.
118    return pid, master_fd
119
120def _writen(fd, data):
121    """Write all the data to a descriptor."""
122    while data:
123        n = os.write(fd, data)
124        data = data[n:]
125
126def _read(fd):
127    """Default read function."""
128    return os.read(fd, 1024)
129
130def _copy(master_fd, master_read=_read, stdin_read=_read):
131    """Parent copy loop.
132    Copies
133            pty master -> standard output   (master_read)
134            standard input -> pty master    (stdin_read)"""
135    fds = [master_fd, STDIN_FILENO]
136    while True:
137        rfds, wfds, xfds = select(fds, [], [])
138        if master_fd in rfds:
139            data = master_read(master_fd)
140            if not data:  # Reached EOF.
141                fds.remove(master_fd)
142            else:
143                os.write(STDOUT_FILENO, data)
144        if STDIN_FILENO in rfds:
145            data = stdin_read(STDIN_FILENO)
146            if not data:
147                fds.remove(STDIN_FILENO)
148            else:
149                _writen(master_fd, data)
150
151def spawn(argv, master_read=_read, stdin_read=_read):
152    """Create a spawned process."""
153    if type(argv) == type(''):
154        argv = (argv,)
155    sys.audit('pty.spawn', argv)
156    pid, master_fd = fork()
157    if pid == CHILD:
158        os.execlp(argv[0], *argv)
159    try:
160        mode = tty.tcgetattr(STDIN_FILENO)
161        tty.setraw(STDIN_FILENO)
162        restore = 1
163    except tty.error:    # This is the same as termios.error
164        restore = 0
165    try:
166        _copy(master_fd, master_read, stdin_read)
167    except OSError:
168        if restore:
169            tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)
170
171    os.close(master_fd)
172    return os.waitpid(pid, 0)[1]
173