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

int main()
{
	int fds[2];
	pid_t pid;

	/*	Create a pipe. File descriptors for the two ends of
		the pipe are placed in fds*/
	pipe(fds);
	/* 	Fork a child process. */
	pid = fork();
	if(pid == (pid_t) 0){
		/*	This is the child process. Close our copy of the
			write end of the file descriptor. */
		close(fds[1]);
		/*	Connect the read end of the pipe to standard input. */
		dup2(fds[0], STDIN_FILENO);
		/*	Replace the child process with the "sort" program. 	*/
		execlp("sort", "sort", 0);
	} else{
		/*	This is the parent process. */
		FILE* stream;
		/* 	Close our copy of the read end of the file descriptor. */
		close(fds[0]);
		/*	Convert the write file descriptor to a FILE object,
			and write to it */
		stream = fdopen(fds[1], "w");
		fprintf(stream, "This is a test.\n");
		fprintf(stream, "Hello, world.\n");
		fprintf(stream, "This program works.\n");
		fflush(stream);
		close(fds[1]);
		/*	Wait for the child process to finish. */
		waitpid(pid, NULL, 0);
	}
	return 0;
}