What signals exist in the Linux operating system…

POSIX-compatible signals:

SIGINT: Interrupt request from the user (Ctrl+C).
SIGTERM: Request to terminate the program.
SIGKILL: Unconditional termination of the program (cannot be caught).
SIGQUIT: Request to terminate and dump memory (Ctrl+).
SIGHUP: Hangup detected on controlling terminal; restart daemon.
SIGFPE: Arithmetic error (e.g., division by zero).
SIGSEGV: Segmentation fault (invalid memory access).
SIGBUS: Bus error (invalid memory access).
SIGILL: Illegal instruction.
SIGTRAP: Trace/breakpoint trap.
SIGABRT: Abort signal (e.g., from abort()).
SIGUSR1, SIGUSR2: User-defined signals (for applications).
SIGSTOP: Stop process (cannot be caught).
SIGTSTP: Stop process from terminal (Ctrl+Z).
SIGCONT: Continue a stopped process.
SIGCHLD: Child process status change.
SIGTTIN: Background process reading from terminal.
SIGTTOU: Background process writing to terminal.
SIGPOLL (SIGIO): I/O now possible on a file descriptor.
SIGPROF: Profiling timer expired.
SIGSYS: Bad system call.
SIGURG: Urgent condition on socket.
SIGVTALRM: Virtual timer expired.
SIGXCPU: CPU time limit exceeded.
SIGXFSZ: File size limit exceeded.

Real-time signals: Start from SIGRTMIN and end with SIGRTMAX. They are used for specific scheduling and communication tasks between processes, with their numbers depending on the implementation.

Signal handling in Python:

import signal
import os
import time

def handler(signum, frame):
    # Signal handler
    print(f"\nReceived signal: {signal.Signals(signum).name}")
    if signum == signal.SIGTERM:
        print("Terminating gracefully...")
        # Code for clean shutdown can be placed here
        exit(0)

# Setting handlers for SIGTERM and SIGINT
signal.signal(signal.SIGTERM, handler)
signal.signal(signal.SIGINT, handler)

print(f"My PID: {os.getpid()}")
print("Press Ctrl+C or send SIGTERM...")

while True:
    # Program runs
    time.sleep(1)
    print("Working...")

Sending signals from the command line:

# Send SIGTERM to process with PID 12345
kill 12345

# Send SIGKILL to process with PID 12345
kill -9 12345

# Send SIGINT (equivalent to Ctrl+C)
# In another terminal window, if the process is not running in background
# kill -INT <PID>

What signals exist in the Linux operating system?