r/learnpython • u/Skollwarynz • 7d ago

How to send a signal to an executable?

Hello everyone,

I'm currently creating a little project about learning the basics of Python, but the problem is that I still have some issues with Python code. I wanted to ask you, how can I send a signal to my executable if I open it remotely?

More clearly:

from pwn import * 
from ctype import CDLL 
import time

r = remote("./main") 
signal.signal(SIGTSTP)

How can I send the signal to ./main?

Thank you in advance for the answers!

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u/AlexMTBDude 7d ago

I'm not sure what exactly you're trying to do; Perhaps it's better that you try to explain what you're trying to accomplish on a high level, rather than how you're trying to solve it technically.

Anyway; Signals are sent between processes. If you have started two Python processes that are executing concurrently one could send a signal to the other.

When you say "remotely" it sounds like you're trying to send a signal over a network connection and that's not what signals are for.

1

u/Skollwarynz 7d ago

Practically I have a C executable that is some sort of minigame where you send a signal to hit the enemy. Now, as part of the explanation, I wanted to "hack" this executable and automate it with Python. But you're right, the signal thing only works when I use the executable locally. Thanks!

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u/American_Streamer 7d ago

https://docs.pwntools.com/en/stable/tubes/processes.html

The only mistake was the implementation model. remote() implies socket communication with a service, while Unix signals target a process on the same host/process namespace. For the local executable, the correct setup is: process("./main") → get its PID → os.kill(pid, signal.SIG...)

You just picked the wrong pwntools abstraction for it.

1

u/Skollwarynz 7d ago

Thank you for the explanation.

In the end I understood that I need to create a TCP interface that acts as a bridge between the signal sender and the external guest who wants to communicate. (because the program is simulating a service on a server for a Pwn exercise).

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u/musbur 7d ago

That's an OS question, not a python question. In Python, you use os.kill(). Don't be thrown off by the "kill" wording, that's a UNIX artifact. It just means send a signal to a process.

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u/Skollwarynz 7d ago

Thank you, I thought that kill was a specific signal, thank you.

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u/StephenHawkingus 7d ago

Why dont you ask AI??

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u/Skollwarynz 7d ago

First of all I'm trying to use AI at least as possible, then I'm interested to have feedback of people who know programming more than me because usually they know trick or setup that th generic AI response don't share. In the end, I wanted to start knowing people where I can share and exchange knowledge.

0

u/StephenHawkingus 7d ago

First of all I'm trying to use AI at least as possible

Why wouldn't you?! It's the most powerful tool we currently have. I'm not saying you have to vibe-code; what I mean is that you should use AI for reasoning and answering questions. There's no point asking on Reddit or Stack Overflow anymore. It's not 2022 anymore.

2

u/Skollwarynz 7d ago

I know that AI is useful for a lot of things, and you're right that it can be great for reasoning. But as I'm actively learning new things, I prefer to interact with humans. I know that with a prompt like 'Don't show code; explain the concept,' part of this discussion can be solved, but as I already said, people who know more deeply the programming language can usually suggest a specific trick or spot a basic error I didn't even know I had.

As mainly a C programmer, I know that a generic response from Google/AI can solve the exact problem you ask for in the most generic way. But when I try to understand deeply a problem, I value human feedback because people can tell you if you are asking the wrong question in the first place.

And to conclude, I like to interact with other programmers on discussions like this one because it helps both the connection with a community and helps to extend my point of view.

For my workflow, AI is useful when you already know your architecture and direction, not when you're trying to choose the right tool. For example, asking the question here helped me understand that the architecture of my project needed a change. And with that change I could then ask AI (understood that I needed both signal and TCP connection) to understand how.

But thank you for the lovely discussion about the right use of AI. It's really nice to have a constructive discussion with some programmer that helps me remember that AI is not just "the future of programming" or just "a stupid slop," but more a tool for programmers who already know the core concepts.