Explain what signals are in the Linux operating system and how to work with them.

In Linux, signals are a mechanism for asynchronous notification of processes about events (for example, interruption, termination of a child process, timeout).

Main points:

• Signals have numeric identifiers (e.g., SIGINT, SIGTERM).
• A process can handle a signal using a signal handler or ignore it.
• If a signal is not handled, the default action is applied (for example, process termination).

Example of handling SIGINT (Ctrl+C) in C:

#include <signal.h>
#include <stdio.h>
#include <unistd.h>

void handler(int signum) {
    printf("Received signal %d, terminating\n", signum);
    _exit(0);
}

int main() {
    signal(SIGINT, handler);
    while(1) {
        printf("Working...\n");
        sleep(1);
    }
    return 0;
}

In shell, signals can be sent using the kill command by PID, for example, kill -SIGTERM 1234.