求问下关于管道的四个函数的填写方法?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<ctype.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/wait.h>
#include<sys/stat.h>

#include<errno.h>
#include<assert.h>

#define ERROR_MSG(x)  fprintf(stderr, "%s\n", (x))

#define BUF_SIZE    1024
#define MAX_TASKS   10

typedef struct program_tag {
    char**   args;      // array of pointers to arguments                              
    int      num_args;  // number of arguments                                         
    int      pid;       // process ID of this program                                  
    int      fd_in;     // FD for stdin                                                
    int      fd_out;    // FD for stdout                                               
} Program;

void start_program(Program *progs, int total, int cur)
{
    // TODO
    int i=0;     
    for(;i<total;i++){
if(i==cur){

    }else{

      }
  }

}

int wait_on_program(Program *prog)
{

    return 0;
}


void prepare_pipes(Program *prog, int num_programs)
{
    // TODO
   int i=0;    
   for(i=0;i<num_programs;i++){
           prog[i].pid = i;
           prog[i].fd_in = i-1;
           prog[i].fd_out =i+1;
   }                                   

}


void cleanup_programs(Program *prog, int num_programs)
{
    // TODO                
   for(int i=0;i<num_programs;i++){
      free(prog->args[i]);
   }                                                            
}


void init_program(Program *prog, int na)
{
    // allocate memory for array of arguments                                          
    prog->args = malloc(na * sizeof(char *));
    assert(prog->args != NULL);
    prog->num_args = 0;
    prog->pid = prog->fd_in = prog->fd_out =  -1;
}

int main(int argc, char **argv)
{
    Program progs[MAX_TASKS];
    int     num_programs;

    if (argc <= 1) {
        ERROR_MSG("Specify at least one program to run. Multiple programs are separate\
d by --");
        exit(-1);
    }

    fprintf(stderr, "Parent started. pid=%d\n", getpid());

    // Prepare programs and their arguments                                            
    num_programs = 0;
    int     cur_arg = 1;
    while (cur_arg < argc) {

        init_program(&progs[num_programs], argc);

        int     ia;
        for (ia = 0; cur_arg < argc; cur_arg ++) {
            if (!strcmp(argv[cur_arg], "--")) {
                if (num_programs == MAX_TASKS -  1) {
                    ERROR_MSG("Too many programs.");
                    exit(-1);
                }
                if (cur_arg + 1 == argc) {
                    ERROR_MSG("The last program is empty.");
                    exit(-1);
                }
                cur_arg ++;
                break;
            }
            progs[num_programs].args[ia++] = argv[cur_arg];
        }
        if (ia == 0) {
            ERROR_MSG("Empty program.");
            exit(-1);
        }
            progs[num_programs].args[ia] = NULL;
        progs[num_programs].num_args = ia;
        num_programs ++;
    }

    // Prepare pipes                                                                   
    prepare_pipes(progs, num_programs);

    // spawn children                                                                  
    for (int i = 0; i < num_programs; i ++) {
        start_program(progs, num_programs, i);
    }

    // wait for children                                                               
    for (int i = 0; i < num_programs; i ++) {
        fprintf(stderr, "Waiting for child %2d (%5d)...\n", i, progs[i].pid);
        wait_on_program(&progs[i]);
    }

    // cleanup                                                                         
    cleanup_programs(progs, num_programs);

    fprintf(stderr, "Everything is good.\n");
    return 0;
}

求问四个关于管道的函数怎么写好，菜鸟一个，求问大神

https://www.cnblogs.com/advocate/p/3730285.html