manual/examples/pipe.c

   1 #include <sys/types.h>
   2 #include <unistd.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 /* Read characters from the pipe and echo them to @code{stdout}.  */
   7
   8 void
   9 read_from_pipe (int file)
  10 {
  11   FILE *stream;
  12   int c;
  13   stream = fdopen (file, "r");
  14   while ((c = fgetc (stream)) != EOF)
  15     putchar (c);
  16   fclose (stream);
  17 }
  18
  19 /* Write some random text to the pipe. */
  20
  21 void
  22 write_to_pipe (int file)
  23 {
  24   FILE *stream;
  25   stream = fdopen (file, "w");
  26   fprintf (stream, "hello, world!\n");
  27   fprintf (stream, "goodbye, world!\n");
  28   fclose (stream);
  29 }
  30
  31 int
  32 main (void)
  33 {
  34   pid_t pid;
  35   int mypipe[2];
  36
  37 /*@group*/
  38   /* Create the pipe.  */
  39   if (pipe (mypipe))
  40     {
  41       fprintf (stderr, "Pipe failed.\n");
  42       return EXIT_FAILURE;
  43     }
  44 /*@end group*/
  45
  46   /* Create the child process.  */
  47   pid = fork ();
  48   if (pid == (pid_t) 0)
  49     {
  50       /* This is the child process.
  51          Close other end first.  */
  52       close (mypipe[1]);
  53       read_from_pipe (mypipe[0]);
  54       return EXIT_SUCCESS;
  55     }
  56   else if (pid < (pid_t) 0)
  57     {
  58       /* The fork failed.  */
  59       fprintf (stderr, "Fork failed.\n");
  60       return EXIT_FAILURE;
  61     }
  62   else
  63     {
  64       /* This is the parent process.
  65          Close other end first.  */
  66       close (mypipe[0]);
  67       write_to_pipe (mypipe[1]);
  68       return EXIT_SUCCESS;
  69     }
  70 }