#include <signal.h>
#include <stdio.h>
#include <unistd.h> /* for write*/ 
#include <stdlib.h>  /* for exit */
#include <errno.h>  /* for EINTR*/

static void	sig_alrm(int);

#define MAXLINE 200

void  err_sys(char * msg) {
    printf("%s \n", msg);
    exit(-1); 
}

int main(void)
{
    int		n;
    char	line[MAXLINE];
    extern int errno;
    struct sigaction act;
    
      /*if (signal(SIGALRM, sig_alrm) == SIG_ERR)
        err_sys("signal(SIGALRM) error");*/
  
      /* this code is equivalent to the former; however, it allows us
         to change the default action when a blocking system call is called.
         The default is to restart it when a signal comes. Here we force
         it to be interrupted. */
  
    act.sa_handler = sig_alrm;
    sigemptyset(&act.sa_mask);
    act.sa_flags=SA_INTERRUPT;  /* use SA_RESTART to restart system call*/
    sigaction(SIGALRM, &act, NULL);
  
    alarm(2);
      /* 1. There is a race condition here. Think of having this process
         blocked for more than "2" seconds (or the number we set).
         2. If the system call (read) is restarted automatically (default
         action since 2001, the timeout does nothing! */
    if ( (n = read(STDIN_FILENO, line, MAXLINE)) < 0) 
        if (errno!=EINTR)
            err_sys("read error");
        else
            write(STDOUT_FILENO, "Interrumpted\n", 13);
    alarm(0);
    write(STDOUT_FILENO, line, n);
    exit(0);
}

static void sig_alrm(int signo)
{
    printf("Paso la alarma !!!\n");
    return;	/* nothing to do, just return to interrupt the read */
}