/* file: simple_fork1.c

   See comments and questions at the end of this file.
   Compare against simple_fork0.c and simple-fork1.cc.

*/

#define _XOPEN_SOURCE 500

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

int main(int argc, char *argv[])
{
  char pathname [32];
  int i = 0;
  int outfildes;
  FILE *ofstream;

  if (argc < 2) {
    fprintf (stdout, "Please enter a filename or pathname: ");
    if (!gets (pathname)) {
      /* use of gets() is very bad programming here -- Why?
                          ====================             */
      fprintf (stderr, "you must provide a filename\n");
      exit (-1);
    }
  } else strcpy (pathname, argv[1]);
    /* use of strcpy() is very bad programming here -- Why?
                          ====================             */
  if ((outfildes =
       open (pathname, O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR)) == -1) {
    fprintf (stderr,
      "could not open file \"%s\" for writing: %s\n",
      pathname, strerror (errno));
    exit (-2);
  }

  if (!(ofstream = fdopen (outfildes, "w"))) {
    perror ("could not open stream for writing");
    exit (-3);
  }

  while (i < 3) {
    fprintf (stdout, "i = %d in %d\n", i, getpid ());
    fprintf (ofstream, "i = %d in %d\n", i, getpid ());
    fork ();
    i++;
  }

  fclose (ofstream);
  close (outfildes);
  return 0;
}

/* 

   Purpose: 

   Extend the simple_fork0.c to illustrate the effects
   of fork() on bufffered output.

   Illustrate how one opens a named file and associates it
   with a stream in C, versus C++.

   To compile this program:

     gcc -o simple_fork1 simple_fork1.c

   To run this program:

     ./simple_fork1 abc

   Sample terminal output, when the above was done
   on a Linux machine with two CPU's:

[cop4610@websrv forkexec]$ ./simple_fork1 abc
i = 0 in 27398
i = 1 in 27398
i = 1 in 27399
i = 2 in 27398
i = 2 in 27399
i = 2 in 27400
[cop4610@websrv forkexec]$ i = 2 in 27401

   Why is there output after the second prompt?

   Sample output on file "abc", for same run:

i = 0 in 27561
i = 1 in 27562
i = 2 in 27562
i = 0 in 27561
i = 1 in 27562
i = 2 in 27564
i = 0 in 27561
i = 1 in 27562
i = 2 in 27564
i = 0 in 27561
i = 1 in 27562
i = 2 in 27562
i = 0 in 27561
i = 1 in 27561
i = 2 in 27563
i = 0 in 27561
i = 1 in 27561
i = 2 in 27563
i = 0 in 27561
i = 1 in 27561
i = 2 in 27561
i = 0 in 27561
i = 1 in 27561
i = 2 in 27561

   Why are there more lines of output written to the file "abc" than
   to the terminal?

   Why does the C++ version (simple-fork0.cc) not have these extra lines?

   If there is any detail of this program that you cannot figure out,
   ask questions, either in class, on the course discussion board,
   or by e-mail to one of the instructors for this course.

*/