fork download 
  1. #include <unistd.h>
  2. #include <fcntl.h>
  3.  
  4. int main(int argc, char* argv[]) {
  5. 	/**
  6. 	 * pipefd[0]: read end
  7. 	 * pipefd[1]: write end
  8. 	 */
  9. 	int pipefd[2];
  10. 	pid_t cat_pid;
  11. 	pid_t echo_pid;
  12.  
  13. 	if (pipe(pipefd) < 0) {
  14. 		perror("pipe");
  15. 		exit(-1);
  16. 	}
  17.  
  18. 	cat_pid = fork();
  19. 	if (cat_pid == 0) {
  20. 		close(pipefd[1]); /* close unused end */
  21. 		dup2(pipefd[0], 0);
  22. 		execl("/bin/cat", "/bin/cat", NULL);
  23. 		perror("execl /bin/echo");
  24. 		return -1;
  25. 	}
  26.  
  27. 	echo_pid = fork();
  28. 	if (echo_pid == 0) {
  29. 		close(pipefd[0]); /* close unused end */
  30. 		dup2(pipefd[1], 1);
  31. 		execl("/bin/echo", "/bin/echo", argv[0], NULL);
  32. 		perror("execl /bin/echo");
  33. 		return -1;
  34. 	}
  35.  
  36. 	close(pipefd[0]);
  37. 	close(pipefd[1]);
  38. 	waitpid(cat_pid, NULL, 0);
  39. 	waitpid(echo_pid, NULL, 0);
  40. 	return 0;
  41. }
  42.  
Success #stdin #stdout 0s 3756KB
comments (?)
stdin 
123
stdout 
./prog
https://ideone.com/it1rnG
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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