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C program that does not suspend when Ctrl+Z is pressed

  • Difficulty Level : Hard
  • Last Updated : 26 Sep, 2017

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

We can use Unix signal for this. When Ctrl+Z is pressed, SIGTSTP signal is generated.

SIGTSTP signal is sent to a process by its controlling terminal to request it to stop (terminal stop). We can catch this signal and run our own defined signal.
The standard C library function signal() can be used to set up a handler for any of the above signals.

// C program that does not suspend when
// Ctrl+Z is pressed
#include <stdio.h>
#include <signal.h>
// Signal Handler for SIGTSTP
void sighandler(int sig_num)
    // Reset handler to catch SIGTSTP next time
    signal(SIGTSTP, sighandler);
    printf("Cannot execute Ctrl+Z\n");
int main()
    // Set the SIGTSTP (Ctrl-Z) signal handler
    // to sigHandler
    signal(SIGTSTP, sighandler);
    return 0;


Cannot execute Ctrl+Z

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