#include <iostream>

#include <unistd.h>  // get/set hostname
#include <limits.h>   // for HOST_NAME_MAX

//#include <stdio.h>    // perror
#include <errno.h>    //errno

using namespace std;

const int LEN = HOST_NAME_MAX;

int main() {
     char name[LEN];
     char eName[1];

     cout << "Before the call errno is " << errno << endl;
     gethostname(eName, 1);
     cout << "After the first call errno is " << errno << endl;
     sethostname(eName, 1);
     cout << "After the second call errno is " << errno << endl;
     cout << "After the second call errno is " << errno << endl;

     return 0;
}