jade
0c76195351
I was packaging Lix 2.91 for nixpkgs and was annoyed at the expect
dependency. Turns out that you can replace unbuffer with a pretty-short
Python script.
It became less short after I found out that Linux was converting \n to
\r\n in the terminal subsystem, which was not very funny, but is at
least solved by twiddling termios bits.
Change-Id: I8a2700abcbbf6a9902e01b05b40fa9340c0ab90c
78 lines
2.2 KiB
Python
Executable file
78 lines
2.2 KiB
Python
Executable file
#!/usr/bin/env python3
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# SPDX-FileCopyrightText: 2001, 2002, 2003, 2004, 2005, 2006 Python Software Foundation; All Rights Reserved
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# SPDX-FileCopyrightText: 2024 Jade Lovelace
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# SPDX-License-Identifier: LGPL-2.1-or-later
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"""
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This script exists to lose Lix a dependency on expect(1) for the ability to run
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something in a pty.
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Yes, it could be replaced by script(1) but macOS and Linux script(1) have
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diverged sufficiently badly that even specifying a subcommand to run is not the
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same.
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"""
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import pty
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import sys
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import os
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from termios import ONLCR, ONLRET, ONOCR, OPOST, TCSAFLUSH, tcgetattr, tcsetattr
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from tty import setraw
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import termios
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def setup_terminal():
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# does not matter which fd we use because we are in a fresh pty
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modi = tcgetattr(pty.STDOUT_FILENO)
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[iflag, oflag, cflag, lflag, ispeed, ospeed, cc] = modi
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# Turning \n into \r\n is not cool, Linux!
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oflag &= ~ONLCR
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# I don't know what "implementation dependent postprocessing means" but it
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# sounds bad
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oflag &= ~OPOST
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# Assume that NL performs the role of CR; do not insert CRs at column 0
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oflag |= ONLRET | ONOCR
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modi = [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]
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tcsetattr(pty.STDOUT_FILENO, TCSAFLUSH, modi)
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def spawn(argv: list[str]):
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"""
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As opposed to pty.spawn, this one more seriously controls the pty settings.
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Necessary to turn off such fun functionality as onlcr (LF to CRLF).
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This is essentially copy pasted from pty.spawn, since there is no way to
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hook the child pre-execve
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"""
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pid, master_fd = pty.fork()
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if pid == pty.CHILD:
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setup_terminal()
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os.execlp(argv[0], *argv)
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try:
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mode = tcgetattr(pty.STDIN_FILENO)
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setraw(pty.STDIN_FILENO)
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restore = True
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except termios.error:
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restore = False
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try:
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pty._copy(master_fd, pty._read, pty._read) # type: ignore
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finally:
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if restore:
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tcsetattr(pty.STDIN_FILENO, TCSAFLUSH, mode) # type: ignore
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os.close(master_fd)
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return os.waitpid(pid, 0)[1]
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def main():
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if len(sys.argv) == 1:
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print(f'Usage: {sys.argv[0]} [command args]', file=sys.stderr)
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sys.exit(1)
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sys.exit(os.waitstatus_to_exitcode(spawn(sys.argv[1:])))
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if __name__ == '__main__':
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main()
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