Thread: using signals to pause and unpause a program via terminal

I'm writing a program that counts down from a user desired number. it should pause when ctrl-c is pressed and terminated when ctrl-\ is pressed. I cant seem to get it to pause or countdown. Im new to using signals so i may have done it incorectly.

Code:

#include <stdbool.h>
#include <stdio.h>
#include <termios.h>
#include <stdlib.h>
#include <unistd.h>


//global variable
bool cont = true;


//signal handling function
void sigHandler(int signal)
{
    if(signal == SIGINT)
    {
        printf("pausing");
        cont = false;
    }
    else
    {
        cont = false;
    }
}


int main(int argc, const char * argv[])
{
    // install the handler
    signal( SIGINT, sigHandler);
    
    //create terminal interface with termio
    struct termios oldTerm;
    struct termios newTerm;
    //Get the attributes of the terminal
    tcgetattr(0, &oldTerm);
    //If wrong number of arguments
    if(argc != 2)
    {
        printf("Wrong number of arguments. ");
    }
    else
    {
        printf("Initiating Countdown.\n");
        //get the Number from argv
        int startNum = atoi(argv[1]);
        //printf("%d", startNum);
        printf("\n");
        newTerm.c_iflag &= ~IXOFF;
        //set terminal attributes to take effect immediatly
        tcsetattr(1, TCSANOW, &newTerm);
        while(cont)
        {
            printf("%d", startNum);
            fflush(stdout);
            printf("\n");
            sleep(1);
        }
    }
    tcsetattr(1,TCSAFLUSH,&oldTerm);
    return 0;
}

this is my original code im now modifying to use signals.

Code:

#include <stdio.h>
#include <termios.h>
#include <stdlib.h>
#include <unistd.h>


int main(int argc, const char * argv[])
{
    //create terminal interface with termio
    struct termios oldTerm;
    struct termios newTerm;
    //Get the attributes of the terminal
    tcgetattr(0, &oldTerm);
    //If wrong number of arguments
    if(argc != 2)
    {
        printf("Wrong number of arguments. ");
    }
    else
    {
        printf("Initiating Countdown.\n");
        //get the Number from argv
        int startNum = atoi(argv[1]);
        //printf("%d", startNum);
        printf("\n");
        newTerm.c_iflag &= ~IXOFF;
        //Set P to pause countdown
        newTerm.c_cc[VSTOP] = 'p';
        //set U to resume countdown
        newTerm.c_cc[VSTART] = 'u';
        //set terminal attributes to take effect immediatly
        tcsetattr(1, TCSANOW, &newTerm);
        //create buffer for int to char conversion
        //char numToWord[25];
        //setvbuf(stdout, (char *)NULL, _IONBF, 0);
        for(; startNum > 0; startNum--)
        {
            //sprintf(numToWord, "%d", startNum);
            printf("%d", startNum);
            fflush(stdout);
            printf("\n");
            sleep(1);
        }
    }
    tcsetattr(1,TCSAFLUSH,&oldTerm);
    return 0;
}

Ohhh i see. The nested while loops were throwing me off when i tried to write that portion because i still wanted to keep my for loop despite while loops making more sense. Thank you for linking linux manual page and your help!