call a function when the program is finished with ctrl c

Question

Hello, I am working in the Linux environment, and I have a C++ program, what I want is when I cancel the program with ctrl+c I would like that the program executes a function, to close some files and print some sutff, is there any way to do this?. Thank you.

Answer 1

Short answer: look into the signal function, specifically catching SIGINT. You write a callback function and pass it to the system via the signal function, then when that particular signal happens, the system calls your callback function. You can close files and do whatever other cleanup stuff you want in there.

Answer 2

You have to catch the SIGINT. Something like this:

void sigint_handler(int sig)
{
    [do some cleanup]
    signal(SIGINT, SIG_DFL);
    kill(getpid(), SIGINT);
}

loads more detail here

Answer 3

For a full working example you can try the following code:

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

volatile bool STOP = false;
void sigint_handler(int sig);

int main() {
    signal(SIGINT, sigint_handler);
    while(true) {
        if (STOP) {
            break;
        }
    }
    return 0;
}

void sigint_handler(int sig) {
    printf("\nCTRL-C detected\n");
    STOP = true;
}

Example run:

[user@host]$ ./a.out 
^C
CTRL-C detected

Answer 4

Note to people who might stumble upon this question, looking for the answer in Windows instead:

Use the SetConsoleCtrlHandler API call to set a custom handler and watch for CTRL_C_EVENT, CTRL_BREAK_EVENT or CTRL_CLOSE_EVENT.

Answer 5

signal() can be dangerous on some OSes and is deprecated on Linux in favor of sigaction(). "signal versus sigaction"

Here's an example that I ran across recently ("Tap the interrupt signal") and modified as I was playing around with it.

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

struct sigaction old_action;

void sigint_handler(int sig_no)
{
    printf("CTRL-C pressed\n");
    sigaction(SIGINT, &old_action, NULL);
    kill(0, SIGINT);
}

int main()
{

    struct sigaction action, old_action;
    memset(&action, 0, sizeof(action));
    action.sa_handler = &sigint_handler;
    sigaction(SIGINT, &action, &old_action);

    pause();

    return 0;
}