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

int global;

void *handleInput(void*);

int main() {
        pthread_t inputHandler;         //basically our thread ID

        //create thread
        if(pthread_create(&inputHandler, NULL, handleInput, NULL))
                perror("Failed to spawn inputHandler thread");

        global = 1;
        sleep(1);
        printf("Global = %i\n", global);

        //send SIGUSR1 signal to our input handler
        pthread_kill(inputHandler, SIGUSR1);

        //wait for inputHandler to return
        pthread_join(inputHandler, NULL);
        
        printf("Global = %i\n", global);
        pthread_detach(inputHandler);
        return 0;
}

//The thread will jump into this function
void *handleInput(void *lol) {
        int signo;

        //Let's add the signal SIGUSR1 to the set of signals we're waiting for
        sigset_t set;
        sigemptyset(&set);
        sigaddset(&set, SIGUSR1);

        //block until SIGUSR1 is received
        while(!sigwait(&set, &signo)) {
                global=5;
                return;
        }
}

/*Output
john@lenin:~/school/cs4061/sandbox$ gcc threadsig.c -lpthread
john@lenin:~/school/cs4061/sandbox$ ./a.out
Global = 1
Global = 5
john@lenin:~/school/cs4061/sandbox$ 
*/