c++ tolower command line tool

tolower.cpp

#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>

using namespace std;

int main(int argc, char *argv[]) {
  if (argc < 2) {
    exit(1);
  }
  string input = argv[1];
  transform(input.begin(), input.end(), input.begin(), towlower);
  cout << input << endl;
}