
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

/* @r{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);
@}

/* @r{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
  /* @r{Create the pipe.} */
  if (pipe (mypipe))
    @{
      fprintf (stderr, "Pipe failed.\n");
      return EXIT_FAILURE;
    @}
@end group

  /* @r{Create the child process.} */
  pid = fork ();
  if (pid == (pid_t) 0)
    @{
      /* @r{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)
    @{
      /* @r{The fork failed.} */
      fprintf (stderr, "Fork failed.\n");
      return EXIT_FAILURE;
    @}
  else
    @{
      /* @r{This is the parent process.
         Close other end first.} */
      close (mypipe[0]);
      write_to_pipe (mypipe[1]);
      return EXIT_SUCCESS;
    @}
@}
