/* Creating a Pipe

   Copyright (C) 1991-2018 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or

   modify it under the terms of the GNU General Public License

   as published by the Free Software Foundation; either version 2

   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, if not, see <http://www.gnu.org/licenses/>.

*/

#include <sys/types.h>

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

/* Read characters from the pipe and echo them to @code{stdout}.  */

void

read_from_pipe (int file)

{

  FILE *stream;

  int c;

  stream = fdopen (file, "r");

  while ((c = fgetc (stream)) != EOF)

    putchar (c);

  fclose (stream);

}

/* Write some random text to the pipe. */

void

write_to_pipe (int file)

{

  FILE *stream;

  stream = fdopen (file, "w");

  fprintf (stream, "hello, world!\n");

  fprintf (stream, "goodbye, world!\n");

  fclose (stream);

}

int

main (void)

{

  pid_t pid;

  int mypipe[2];

/*@group*/

  /* Create the pipe.  */

  if (pipe (mypipe))

    {

      fprintf (stderr, "Pipe failed.\n");

      return EXIT_FAILURE;

    }

/*@end group*/

  /* Create the child process.  */

  pid = fork ();

  if (pid == (pid_t) 0)

    {

      /* This is the child process.

	 Close other end first.  */

      close (mypipe[1]);

      read_from_pipe (mypipe[0]);

      return EXIT_SUCCESS;

    }

  else if (pid < (pid_t) 0)

    {

      /* The fork failed.  */

      fprintf (stderr, "Fork failed.\n");

      return EXIT_FAILURE;

    }

  else

    {

      /* This is the parent process.

	 Close other end first.  */

      close (mypipe[0]);

      write_to_pipe (mypipe[1]);

      return EXIT_SUCCESS;

    }

}