source: testjes/ranpw.cpp @ 10

#include <iostream>
#include <stdlib.h>
#include <algorithm>
#include <sys/time.h>
void gen_random(std::string &s, const int len) {
 timeval t1;
 gettimeofday(&t1, NULL);
 std::srand(t1.tv_usec * t1.tv_sec);
 static const char alphanum[] =
   "0123456789"
   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
   "abcdefghijklmnopqrstuvwxyz";

  s.resize(len);
  for (int i = 0; i < len; ++i) {
      s[i] = alphanum[std::rand() % (sizeof(alphanum) - 1)];
  }
}
int main()
{
  std::string s;
  for (int i=0; i<6; i++)
  {
    gen_random(s,8);
    std::cout << s << " ";
  }
  std::cout << std::endl;
}