Linux Signal Demonstrations

A collection of C programs demonstrating Linux Signals. This project shows how to catch SIGINT (Ctrl+C), ignore signals, and use signals for basic Inter-Process Communication (IPC).

Inspired by the 'Core Dumped' YouTube channel: Signals: Make Ctrl+C Do Anything You Want

---

🛠️ How to Compile and Run

This project includes a Makefile to simplify compilation. You will need gcc (or clang) and make installed.

1. Clone the repository (or download and extract the files).

2. Create the build directory:

   mkdir build

3. Compile all programs:

   make all

4. Run a specific example (see below).

5. To clean up compiled files:

   make clean

---

🚀 The Examples

1. src/01-catch-sigint.c

• What it does: Demonstrates how to "catch" the SIGINT signal (sent by Ctrl+C).
• How it works: Instead of quitting, the program catches the signal and prints a message ("Ouch! Don't do that!"). It keeps a counter and will only exit after you press Ctrl+C 5 times.
• To Run:

  ./build/01-catch-sigint

2. src/02-ignore-signal.c

• What it does: Shows how to completely ignore a signal.
• How it works: This program tells the OS to ignore SIGINT. When you press Ctrl+C, nothing happens. It prints its own PID so you can stop it.
• To Run:

  ./build/02-ignore-signal

• To Stop: You must open a second terminal and use the kill -9 command with the PID it printed.

  kill -9 <PID_from_program>

3. src/03-ipc-demo/

• What it does: A two-part demo showing how signals are used for Inter-Process Communication (IPC).
• How it works:
  1. Run the receiver in one terminal. It will print its PID and wait.
  2. Run the sender in a second terminal, giving it the receiver's PID as an argument.
  3. The sender uses the kill() system call to send a SIGUSR1 signal.
  4. The receiver catches this signal and prints ">>> Signal Received! <<<".
• To Run (Terminal 1):

  ./build/receiver
  # It will print: Receiver PID is: 12345

• To Run (Terminal 2):

  # Use the PID from Terminal 1
  ./build/sender 12345

---

Output

--

--