#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>

void run_pipe(char  **command);
int  pipes[4], pipeline;

int main(void){
	
	char* cmd1[]={"cat",  "data", NULL};
	char* cmd2[]={"grep", "int" , NULL};
	char* cmd3[]={"cut",  "-b", "1-10", NULL};
	
	pipeline = 0;
	pipe(pipes);
	pipe(pipes + 2);
	
	run_pipe(cmd1);	
	run_pipe(cmd2);
	run_pipe(cmd3);
}

void run_pipe(char  **command){
  	int status, j;

  	if (!command)	return;

	switch (pipeline){
		case 0:	dup2(pipes[1], 1);	break;

		case 1:	
                     pipe(pipes + 2);
                     dup2(pipes[0], 0);
                     dup2(pipes[3], 1);
                     break;

		case 2:	
                     pipe(pipes);
                     dup2(pipes[2], 0);
                     dup2(pipes[1], 1);
                     break;

	}  for (j=0; j<4; j++) 
		close(pipes[j]);

	if (fork() == 0){
		execvp(*command, command);
	}

	wait(&status);

	pipeline++;
	if (pipeline == 3)	pipeline = 1;
}

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

void run_pipe(char **path, int read_fd, int write_fd);

int main (int argc, char **argv){
	
	int i;
	int pipe_count = 2;
	int proc_count = 3;
	int (*pipes)[2] = malloc(sizeof(*pipes) * pipe_count);

	char *cmd1 [] = {"cat",  "test2.c",    NULL};
	char *cmd2 [] = {"grep", "printf",     NULL};
	char *cmd3 [] = {"cut",  "-b", "1-6",  NULL};
       
	for (i = 0; i < pipe_count; i++)	pipe(pipes[i]);
        
    for (i = 0; i < proc_count; i++) {
		
		if (i == 0){						
            run_pipe(cmd1, 0, pipes[i][1]);
        }else if (i < proc_count - 1){		
           run_pipe(cmd2,	 pipes[i-1][0], pipes[i][1]);
        }else{								
             run_pipe(cmd3,	 pipes[i-1][0], 0);}
    }
}

void run_pipe(char **path, int read_fd, int write_fd){
        
	int pid = fork();

    if (pid){		//parent
		if (read_fd)	close(read_fd);
        if (write_fd)	close(write_fd);
        return;
    }

    if (read_fd)		dup2(read_fd , 0);
    if (write_fd)		dup2(write_fd, 1);

    execvp(*path, path);
}