Linux C programming, choose Popen () to get a relative path of absolute path __ block chain

Linux C programming, get a relative path of the absolute path, the following program is very simple, you can encapsulate it into a function, sometimes used in the work.

#include <iostream>
using namespace Std;
#include <unistd.h>
#include <cstring>

int main ()
{
String Dir_path = "./.. /..          /"; Relative path
std::string command = "CD" +dir_path + "; pwd; ";
FILE *pp=null;
if (pp = Popen (Command.c_str (), "r") = = NULL)
{
return-1;
}

Char buf[333] = {0};
Fgets (buf, sizeof (BUF), pp);

printf ("%s", buf); Print absolute path
Pclose (PP);

When the task is complete, the current absolute path is not changed.
System ("PWD");
return 0;
}