/*-------------------------------------------------------------------*/
/* testlowlevelio.c                                                  */
/* The creat, open, write, read, and close system calls.             */
/*-------------------------------------------------------------------*/

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

int main(int argc, char *argv[])
{
   int iFd;
   int iRet;
   int iBytesWritten;
   int iBytesRead;
   char pcWriteBuffer[] = "hello";
   char pcReadBuffer[6];

   /* Write "hello" to a file named tempfile. */

   iFd = creat("tempfile", 0644);
   if (iFd == -1)
   {
      perror(argv[0]);
      return 1;
   }

   iBytesWritten = 0;
   while (iBytesWritten < 6)
   {
      iRet = write(iFd, pcWriteBuffer + iBytesWritten, 6 - iBytesWritten);
      if (iRet == -1)
      {
         perror(argv[0]);
         return 1;
      }
      iBytesWritten += iRet;
   }

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

   /* Read "hello" from a file named tempfile. */

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

   iBytesRead = 0;
   while (iBytesRead < 6)
   {
      iRet = read(iFd, pcReadBuffer + iBytesRead, 6 - iBytesRead);
      if (iRet == -1)
      {
         perror(argv[0]);
         return 1;
      }
      iBytesRead += iRet;
   }

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

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

   printf("%s\n", pcReadBuffer);
   return 0;
}


/* Sample execution:

--> gcc -Wall -ansi -pedantic -o testlowlevelio testlowlevelio.c
--> testlowlevelio
hello
-->

*/