Unix, creating and stopping processes

/*
Задание: обработка сигналов SIGQUIT, SIGINT, SIGTTIN.
Сборка:
gcc one.c -o one.out
gcc two.c -o two.out
./two.out
*/
/// two.c:
// includes:
#include <stdlib.h> // exit(code)
#include <stdio.h>  // printf(...), scanf(...)
#include <unistd.h> // execl()
#include <signal.h> // sig, kill, ...

int main(int agrc, char *argv[]) {
    int code, input; // return code, input number
    pid_t pid; // process id of child process
    // display sort of menu:
    printf("What will you do?\n");
    printf("1 - SIGQUIT (end process 'on its own')\n");
    printf("2 - SIGINT (end process)\n");
    printf("3 - SIGTTIN (stop process)\n");
    scanf("%i", &input);
    pid = fork(); // fork process
    switch (pid) { // do depending on result of fork
    case -1: // fork fail
        printf(" ~ Failed to fork");
        exit(1);
        break;
    case 0: // child process:
        if ((execl("one.out", "1", NULL)) == -1) break;
        // Error in execl.
        perror("\n ~ Error in execl()");
        printf("\n ~ Did you try 'gcc one.c -o one.out'?");
        exit(1);
    default: // parent process:
        switch(input) { // send code depending on input
        case 1:
            kill(pid, SIGQUIT);
            break;
        case 2:
            kill(pid, SIGINT);
            break;
        case 3:
            kill(pid, SIGTTIN);
            break;
        }
        wait(&code); // wait until child process finishes
        switch (code) { // display text depending on returned code:
        case SIGQUIT:
            printf("Process ended by SIGQUIT.");
            break;
        case SIGINT:
            printf("Process ended by SIGINT.");
            break;
        default:
            printf("Process ended.");
        }
        printf(" Returned code %d\n", code);
        break;
    }
}
/// one.c:
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
// procedure to make process end 'by itself':
void do_exit() {
    exit(1);
}

int main(int agrc, char *argv[])
{
    struct sigaction sa;
    sigset_t signal_set;
    // try to set signal
    if(signal(SIGTTIN, do_exit) < 0) {
        perror("Error setting signal");
    }
    for(;;) { // wait until stopped by host.
        sleep(1);
    }
}