Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 1 | """Pseudo terminal utilities.""" |
| 2 | |
| 3 | # Bugs: No signal handling. Doesn't set slave termios and window size. |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 4 | # Only tested on Linux, FreeBSD, and macOS. |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 5 | # See: W. Richard Stevens. 1992. Advanced Programming in the |
| 6 | # UNIX Environment. Chapter 19. |
| 7 | # Author: Steen Lumholt -- with additions by Guido. |
| 8 | |
| 9 | from select import select |
| 10 | import os |
| 11 | import sys |
| 12 | import tty |
| 13 | |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 14 | # names imported directly for test mocking purposes |
| 15 | from os import close, waitpid |
| 16 | from tty import setraw, tcgetattr, tcsetattr |
| 17 | |
| 18 | __all__ = ["openpty", "fork", "spawn"] |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 19 | |
| 20 | STDIN_FILENO = 0 |
| 21 | STDOUT_FILENO = 1 |
| 22 | STDERR_FILENO = 2 |
| 23 | |
| 24 | CHILD = 0 |
| 25 | |
| 26 | def openpty(): |
| 27 | """openpty() -> (master_fd, slave_fd) |
| 28 | Open a pty master/slave pair, using os.openpty() if possible.""" |
| 29 | |
| 30 | try: |
| 31 | return os.openpty() |
| 32 | except (AttributeError, OSError): |
| 33 | pass |
| 34 | master_fd, slave_name = _open_terminal() |
| 35 | slave_fd = slave_open(slave_name) |
| 36 | return master_fd, slave_fd |
| 37 | |
| 38 | def master_open(): |
| 39 | """master_open() -> (master_fd, slave_name) |
| 40 | Open a pty master and return the fd, and the filename of the slave end. |
| 41 | Deprecated, use openpty() instead.""" |
| 42 | |
| 43 | try: |
| 44 | master_fd, slave_fd = os.openpty() |
| 45 | except (AttributeError, OSError): |
| 46 | pass |
| 47 | else: |
| 48 | slave_name = os.ttyname(slave_fd) |
| 49 | os.close(slave_fd) |
| 50 | return master_fd, slave_name |
| 51 | |
| 52 | return _open_terminal() |
| 53 | |
| 54 | def _open_terminal(): |
| 55 | """Open pty master and return (master_fd, tty_name).""" |
| 56 | for x in 'pqrstuvwxyzPQRST': |
| 57 | for y in '0123456789abcdef': |
| 58 | pty_name = '/dev/pty' + x + y |
| 59 | try: |
| 60 | fd = os.open(pty_name, os.O_RDWR) |
| 61 | except OSError: |
| 62 | continue |
| 63 | return (fd, '/dev/tty' + x + y) |
| 64 | raise OSError('out of pty devices') |
| 65 | |
| 66 | def slave_open(tty_name): |
| 67 | """slave_open(tty_name) -> slave_fd |
| 68 | Open the pty slave and acquire the controlling terminal, returning |
| 69 | opened filedescriptor. |
| 70 | Deprecated, use openpty() instead.""" |
| 71 | |
| 72 | result = os.open(tty_name, os.O_RDWR) |
| 73 | try: |
| 74 | from fcntl import ioctl, I_PUSH |
| 75 | except ImportError: |
| 76 | return result |
| 77 | try: |
| 78 | ioctl(result, I_PUSH, "ptem") |
| 79 | ioctl(result, I_PUSH, "ldterm") |
| 80 | except OSError: |
| 81 | pass |
| 82 | return result |
| 83 | |
| 84 | def fork(): |
| 85 | """fork() -> (pid, master_fd) |
| 86 | Fork and make the child a session leader with a controlling terminal.""" |
| 87 | |
| 88 | try: |
| 89 | pid, fd = os.forkpty() |
| 90 | except (AttributeError, OSError): |
| 91 | pass |
| 92 | else: |
| 93 | if pid == CHILD: |
| 94 | try: |
| 95 | os.setsid() |
| 96 | except OSError: |
| 97 | # os.forkpty() already set us session leader |
| 98 | pass |
| 99 | return pid, fd |
| 100 | |
| 101 | master_fd, slave_fd = openpty() |
| 102 | pid = os.fork() |
| 103 | if pid == CHILD: |
| 104 | # Establish a new session. |
| 105 | os.setsid() |
| 106 | os.close(master_fd) |
| 107 | |
| 108 | # Slave becomes stdin/stdout/stderr of child. |
| 109 | os.dup2(slave_fd, STDIN_FILENO) |
| 110 | os.dup2(slave_fd, STDOUT_FILENO) |
| 111 | os.dup2(slave_fd, STDERR_FILENO) |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 112 | if slave_fd > STDERR_FILENO: |
| 113 | os.close(slave_fd) |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 114 | |
| 115 | # Explicitly open the tty to make it become a controlling tty. |
| 116 | tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR) |
| 117 | os.close(tmp_fd) |
| 118 | else: |
| 119 | os.close(slave_fd) |
| 120 | |
| 121 | # Parent and child process. |
| 122 | return pid, master_fd |
| 123 | |
| 124 | def _writen(fd, data): |
| 125 | """Write all the data to a descriptor.""" |
| 126 | while data: |
| 127 | n = os.write(fd, data) |
| 128 | data = data[n:] |
| 129 | |
| 130 | def _read(fd): |
| 131 | """Default read function.""" |
| 132 | return os.read(fd, 1024) |
| 133 | |
| 134 | def _copy(master_fd, master_read=_read, stdin_read=_read): |
| 135 | """Parent copy loop. |
| 136 | Copies |
| 137 | pty master -> standard output (master_read) |
| 138 | standard input -> pty master (stdin_read)""" |
| 139 | fds = [master_fd, STDIN_FILENO] |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 140 | while fds: |
| 141 | rfds, _wfds, _xfds = select(fds, [], []) |
| 142 | |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 143 | if master_fd in rfds: |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 144 | # Some OSes signal EOF by returning an empty byte string, |
| 145 | # some throw OSErrors. |
| 146 | try: |
| 147 | data = master_read(master_fd) |
| 148 | except OSError: |
| 149 | data = b"" |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 150 | if not data: # Reached EOF. |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 151 | return # Assume the child process has exited and is |
| 152 | # unreachable, so we clean up. |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 153 | else: |
| 154 | os.write(STDOUT_FILENO, data) |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 155 | |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 156 | if STDIN_FILENO in rfds: |
| 157 | data = stdin_read(STDIN_FILENO) |
| 158 | if not data: |
| 159 | fds.remove(STDIN_FILENO) |
| 160 | else: |
| 161 | _writen(master_fd, data) |
| 162 | |
| 163 | def spawn(argv, master_read=_read, stdin_read=_read): |
| 164 | """Create a spawned process.""" |
| 165 | if type(argv) == type(''): |
| 166 | argv = (argv,) |
| 167 | sys.audit('pty.spawn', argv) |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 168 | |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 169 | pid, master_fd = fork() |
| 170 | if pid == CHILD: |
| 171 | os.execlp(argv[0], *argv) |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 172 | |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 173 | try: |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 174 | mode = tcgetattr(STDIN_FILENO) |
| 175 | setraw(STDIN_FILENO) |
| 176 | restore = True |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 177 | except tty.error: # This is the same as termios.error |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 178 | restore = False |
| 179 | |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 180 | try: |
| 181 | _copy(master_fd, master_read, stdin_read) |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 182 | finally: |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 183 | if restore: |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 184 | tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode) |
Jingwen Chen | 475b3cc | 2021-01-05 21:45:16 -0500 | [diff] [blame] | 185 | |
Dan Willemsen | c9fa001 | 2022-03-25 22:58:53 +0000 | [diff] [blame] | 186 | close(master_fd) |
| 187 | return waitpid(pid, 0)[1] |