dup2实现重定向 ls --help |more

#include
#include
#include

int main()
{
 pid_t pid;
 int fds[2];
 if((pipe(fds))==-1)
 {
  perror("pipe error");
  exit(EXIT_FAILURE);
 }
 else
 {
  pid=fork();
  if(pid==-1)
  {
   perror("fork error");
   exit(EXIT_FAILURE);
  }
  else if(pid==0)
  {
   close(fds[0]);//close the parent prcoess writer operation
   dup2(fds[1],1);//read the data from the pipe
   
   execlp("ls","ls","--help",NULL);
   perror("dup2 error");
   exit(EXIT_SUCCESS);
  }
  else if(pid > 0)
  {
   close(fds[1]);//close the parent prcoess writer operation
   dup2(fds[0],0);//read the data from the pipe
   
   execlp("more","more",NULL);
   perror("dup2 error");
   exit(EXIT_FAILURE);

  }
 }
 return 0;
}