/*--------------------------------------------------------------------*/
/* testdupin.c                                                        */
/* Author: Bob Dondero
   Modified by Xiaoyan In August 2018
   (add fstat() to check ) the status of a file                         
*/
/*--------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h> /*needed for fstat()*/

/*--------------------------------------------------------------------*/

/* Demonstrate the open(), close(), dup(), and fstat() system-level functions.
   As usual, argc is the command-line argument count, and argv contains
   the command-line arguments.  Return 0. */

int main(int argc, char *argv[])
{
   enum {BUFFER_LENGTH = 100};
   int iFd;
   int iRet;
   char acBuffer[BUFFER_LENGTH];
   struct stat fInfo;

   iFd = open("tmpfile.txt", O_RDONLY);
   if (iFd == -1) {perror(argv[0]); exit(EXIT_FAILURE); }

   iRet = close(0);
   if (iRet == -1) {perror(argv[0]); exit(EXIT_FAILURE); }

   iRet = dup(iFd);
   if (iRet == -1) {perror(argv[0]); exit(EXIT_FAILURE); }

   iRet = close(iFd);
   if (iRet == -1) {perror(argv[0]); exit(EXIT_FAILURE); }

   fgets(acBuffer, BUFFER_LENGTH, stdin);

   /* Write the data to verify that the call of fgets worked. */
   fputs(acBuffer, stdout);

   /* test whether a file descriptor is closed. Print a message if not. */
   if (fstat(iFd, &fInfo)>=0){
      printf("File descriptor %d is not closed!", iFd);
   }
   if (fstat(1, &fInfo)>=0){
      printf("File descriptor %d is not closed!\n", 1);
   }

   
   return 0;
}

/*--------------------------------------------------------------------*/

/* Sample execution (assume tmpfile.txt has only one line which is "testing!!"):

$ gcc217 testdupin.c -o testdupin

$ ./testdupin
testing!!
File descriptor 1 is not closed!
*/