/*------------------------------------------------------------------*/
/* testlowlevelin.c                                                 */
/* Author: Bob Dondero                                              */
/* The open, read, and close system calls.                          */
/*------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
   int iFd;
   int iRet;
   ssize_t iBytesRead;
   ssize_t iTotalBytesRead;
   char pcBuffer[9];
   int i;

   /* Read "somedata\n" from a file named tempfile. */

   iFd = open("tempfile", O_RDONLY);
   if (iFd == -1) {perror(argv[0]); return EXIT_FAILURE; }

   iTotalBytesRead = 0;
   while (iTotalBytesRead < 9)
   {
      iBytesRead =
         read(iFd, pcBuffer + iTotalBytesRead,
              (size_t)(9 - iTotalBytesRead));
      if (iBytesRead == -1) {perror(argv[0]); return EXIT_FAILURE;}
      iTotalBytesRead += iBytesRead;
   }

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

   /* Print the data to verify that the previous worked. */

   for (i = 0; i < 9; i++)
      putchar(pcBuffer[i]);

   return 0;
}

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

/* Sample execution:

$ gcc -Wall -ansi -pedantic testlowlevelin.c -o testlowlevelin

$ testlowlevelin
somedata

*/