CGI Principle Parsing Series three----CGI how to complete get Web server data

Simulates the process of starting CGI on a server-side httpd process,
Full presentation of Get,post method support
Gcc-g Httpd_all.c-o httpd_all.ums;

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>

#define CGI_NAME "Get_post.ums"
#define REQUEST_METHOD "Request_method=post"
#define Request_parameter "Myname=huangzhihui"

int main (int argc, char *argv[])
{
int parent[2],child[2];
if (pipe (parent) < 0)
{
printf ("Create pipe fail.\n");
}

if (pipe (child) < 0)
{
Close (parent[0]);
Close (parent[1]);
printf ("Create pipe fail.\n");
}

 pid_t pid;
 if (pid = fork ()) < 0)
 {
  printf ("fork fail.\n");
 }
 else if (pid > 0)
 {
  /* Parent */
  //Close redundant handles, construct a single function read-write channel
  close (Parent[0]);
  close (child[1]);
  
  //simulates transmitting data to CGI
  ssize_t length = strlen (request_parameter);
  if (Write (parent[1], request_parameter, length)! = length)
  {
   printf ("Write error to pipe\n");
  }
  close (parent[1]);
  
  //wait for the CGI child process to write the data completely,
  //the actual situation should be using Select or Epoll listening
   //usleep (+);

  //simulates receiving data    the CGI response;
  char buff[256] = {0};
  length = Read (child[0], buff, sizeof (buff));
  if (length <= 0)
  {
   printf ("read error from pipe\n");
  }
  else
  {
   printf ("pid%d read data=%u\n%s", Getpid () , length, buff);
  }
  close (child[0]);

  if (Waitpid (PID, NULL, 0) < 0)
  {
   printf ("Waitpid error\n");
  }
  exit (0);
 }
 else
 {
  /* Child */
  
  //Close redundant handles, construct a single-function read-write channel
  close (parent[1]);
  close (child[0]);
  
  //The input end of the redirect pipeline to the standard input
  if (parent[0]! = Stdin_fileno)
  {
   if (dup2 (parent[0), Stdin_fileno)! = Stdin_fileno)
   {
     printf ("Dup2 error to stdin");
   }
   close (parent[0]);
  }

Redirect the output of the pipeline to standard output
if (child[1]! = Stdout_fileno)
{
if (Dup2 (child[1], stdout_fileno)! = Stdout_fileno)
{
printf ("Dup2 error to stdout");
}
Close (child[1]);
}

Overwrite process space, set CGI environment variables
Char content_length[128] = {0};
sprintf (Content_length, "content_length=%u", strlen (Request_parameter));
Char *exec_argv[3] = {request_method, content_length};
if (Execve (CGI_NAME,ARGV,EXEC_ARGV) < 0)
{
printf ("Execl error for%s", cgi_name);
}
Exit (0);
}
Exit (0);
}

CGI Principle Parsing Series three----CGI how to complete get Web server data