Write a C program that doesn’t terminate when Ctrl+C is pressed. It prints a message “Cannot be terminated using Ctrl+c” and continues execution.

We can use signal handling in C for this. When Ctrl+C is pressed, SIGINT signal is generated, we can catch this signal and run our defined signal handler. C standard defines following 6 signals in signal.h header file.

SIGABRT – abnormal termination.
SIGFPE – floating point exception.
SIGILL – invalid instruction.
SIGINT – interactive attention request sent to the program.
SIGSEGV – invalid memory access.
SIGTERM – termination request sent to the program.

Additional signals are specified Unix and Unix-like operating systems (such as Linux) defines more than 15 additional signals. See http://en.wikipedia.org/wiki/Unix_signal#POSIX_signals
The standard C library function signal() can be used to set up a handler for any of the above signals.
/* A C program that does not terminate when Ctrl+C is pressed */
#include
#include

/* Signal Handler for SIGINT */
void sigintHandler(int sig_num)
{
/* Reset handler to catch SIGINT next time.
Refer http://en.cppreference.com/w/c/program/signal */
signal(SIGINT, sigintHandler);
printf(“\n Cannot be terminated using Ctrl+C \n”);
fflush(stdout);
}

int main ()
{
/* Set the SIGINT (Ctrl-C) signal handler to sigintHandler
Refer http://en.cppreference.com/w/c/program/signal */
signal(SIGINT, sigintHandler);

/* Infinite loop */
while(1)
{
}
return 0;
}

Ouput: When Ctrl+C was pressed two times

Cannot be terminated using Ctrl+C

Cannot be terminated using Ctrl+C