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GeezerVison is showing github.com — gh-85984: Add _POSIX_VDISABLE from unistd.h to termios module. by 8vasu · Pull Request #114985 · python/cpython

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@8vasu

@8vasu 8vasu commented Feb 4, 2024 •
edited by bedevere-app Bot
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This follows #102413.

POSIX General Terminal Interface defines Special Control Characters. An example of this is the INTR character, which is usually set to Control-C, which sends the SIGINT signal to interrupt a process running in the terminal.

POSIX General Terminal Interface allows the programmer to disable these characters by setting them to _POSIX_VDISABLE, which is defined in POSIX <unistd.h>. This is how POSIX stty(1) disables special control characters internally; for example, running the following command will disable the INTR character:

stty intr undef

Now hitting Control-C will not send SIGINT to the running process until it is reset using the following command:

stty intr ^c.

At any given point of time, check all terminal settings by running stty -a.

This PR adds _POSIX_VDISABLE to the termios module.

  • Issue: Lib/pty.py major revision #85984

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@8vasu
Add _POSIX_VDISABLE from unistd.h to termios module.
67bd481 
Signed-off-by: Soumendra Ganguly <[email protected]>
@bedevere-app bedevere-app Bot added the awaiting review label Feb 4, 2024
@bedevere-app bedevere-app Bot mentioned this pull request Feb 4, 2024
Lib/pty.py major revision #85984
Open
@blurb-it
📜🤖 Added by blurb_it.
60c95d4
@8vasu

8vasu commented Feb 4, 2024

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@gpshead @encukou

In a previous PR in this series (#101832), I mentioned the idea of writing a Python library that mimics stty(1) to provide a unified, highly convenient, and Pythonic interface to termios and winsize functionalities. While working on this, I noticed the lack _POSIX_VDISABLE in the termios library.

This is not a dependency of the main set of changes of this series in #101833, but since this idea was conceived while working on this issue and since this PR is so small, I did not create a separate issue for this.

I have added a test script as a comment.
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8vasu
8vasu commented Feb 4, 2024
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Comment thread Modules/termios.c
#ifdef _POSIX_VDISABLE
{"_POSIX_VDISABLE", _POSIX_VDISABLE},
#endif

@8vasu 8vasu Feb 4, 2024

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The following script uses termios._POSIX_VDISABLE to disable INTR. Then it calls stty(1) to check if INTR has successfully been disabled.

#!/usr/bin/python3

# Written and tested on Debian GNU/Linux 12 (bookworm) using stty (GNU coreutils) 9.1.

import subprocess
import termios

def stty_intr_value():
    out = subprocess.run(['stty', '-a'], stdout=subprocess.PIPE, text=True).stdout
    s = out.replace(";", " ")
    sub = "intr = "
    i = s.find(sub) + len(sub)
    return s[i:].split()[0]

t = termios.tcgetattr(0)
t[6][termios.VINTR] = bytes([termios._POSIX_VDISABLE])
termios.tcsetattr(0, termios.TCSANOW, t)

assert stty_intr_value() == "<undef>"
print("PASSED")

Hit Control-C after running running above script to see SIGINT not being sent.

Please run stty intr ^c to restore Control-C functionality.

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@8vasu
Merge branch 'main' into termios_posix_vdisable
299d88e
@8vasu

8vasu commented Feb 10, 2024

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@gpshead @encukou Just a gentle reminder. No rush at all.
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gpshead added 2 commits February 11, 2024 02:03
@gpshead
ReSTify the NEWS entry.
e70e309
@gpshead
fix my news typo.
aa71dc7
@gpshead
gpshead enabled auto-merge (squash) February 11, 2024 10:06
@gpshead gpshead self-assigned this Feb 11, 2024
@gpshead
gpshead merged commit bf75f1b into python:main Feb 11, 2024
@bedevere-app bedevere-app Bot removed the awaiting review label Feb 11, 2024
@8vasu

8vasu commented Feb 12, 2024

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@gpshead Thank you so much! I will make my stty-like library available soon and send you a link.
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fsc-eriker pushed a commit to fsc-eriker/cpython that referenced this pull request Feb 14, 2024
@8vasu @gpshead @fsc-eriker
pythongh-85984: Add _POSIX_VDISABLE from unistd.h to termios module. (p…
9d6c9d8 
…ython#114985)

Signed-off-by: Soumendra Ganguly <[email protected]>
Co-authored-by: Gregory P. Smith <[email protected]>
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@8vasu @gpshead
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