mkfifo fifo1
mkfifo fifo2
./es1 fifo1 fifo2

cat > fifo1
write here and my program will print out the lines

/* Scrivere un programma C che prese in input da riga comando il pathname 
 * di molteplici FIFO (almeno 1, numero imprecisato) metta in output tutt
 * o cio' che arriva da qualsiasi di esse. Il programma non deve usare fo
 * rk ma una chiamata a scelta fra select o poll.
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <limits.h>

#define BUFFER PIPE_BUF

int max(int a[], int num_elements)
{
   int i, max = a[0];
   for (i=0; i<num_elements; i++)
   {
     if (a[i] > max)
     {
        max = a[i];
     }
   }
   return (max);
}


int main(int argc, char **argv)
{
    register int i;
    int* fifos;
    int ready_fd;
    int nfds;
    int buff_count,count;
    fd_set fdset,tmpset;
    char buff[BUFFER];
    struct stat buf_fstat;

//    buff = (char *)malloc(sizeof(char)*4096);

    if (argc==1) /* wrong usage of args*/
    {
        printf("Usage: ./a.out 1st-fifo-path [2nd-fifo-path] ... [n-fifo-path]\n");
        return(-1);
    }
    else /* right usage of args */
    {
        FD_ZERO(&fdset); /* clear the fd_set */
        fifos = (int*) malloc(sizeof(int) * (argc-1));

        for (i=0;i<argc-1;i++)
        {
            if ((fifos[i] = open(argv[i+1],O_RDWR|O_NONBLOCK))<0)
            {
                perror("open");
                return(-2);
            }
            else
            {
                if (fstat(fifos[i],&buf_fstat))
                    perror("fstat");
                else if (! S_ISFIFO(buf_fstat.st_mode))
                {
                        printf("%s is not a pipe. Aborting\n",argv[i+1]);
                        return(-2);
                }
                else
                    FD_SET(fifos[i],&fdset);
            }
        }

        nfds = max(fifos,(argc-1))+1;
        memcpy((void *) &tmpset,(void *) &fdset, sizeof(fd_set));

        while (1)
        {
            /* we will use timeout=NULL to block indefinitely */
            if ((ready_fd = select(nfds,&fdset,NULL,NULL,NULL))<0)
                perror("select");
            else
            {
                #ifdef DEBUG
                    printf("ready fd: %d\n",ready_fd);
                #endif
                for (i=0,count=0;count<ready_fd||i<=(argc-1);i++)
                {
                    if (FD_ISSET(fifos[i],&fdset))
                    {
                        count++;
                        #ifdef DEBUG
                            printf("fifo: %d\n",i);
                        #endif
                        if ((buff_count=read(fifos[i],&buff,BUFFER))<0) 
                            perror("read");
                        else
                        {
                            #ifdef DEBUG
                                printf("read %d bytes\n",buff_count);
                            #endif
                            if (write(STDOUT_FILENO, buff, sizeof(char) * (unsigned int) buff_count)<0)
                                perror("write");
                        }
                    }      
                }
                memcpy((void *) &fdset,(void *) &tmpset, sizeof(fd_set));
            }
        }
    }
}