// head.cc    g++ -g -o head head.cc
// example of command line arguments in C++ and named files
// Usage:   head -20 file1 file2 ...
// This would output the first 20 lines of each file
// Default number of lines is 10.

#include <fstream>  // named files
#include <stdlib.h> // atoi()
#include <iostream>
#include <string>
using namespace std;
int main( int argc, char* argv[] ) {
 int nlines = 10;
 for( int i = 1; i < argc; i++ )
  if ( *argv[i] == '-' )
   nlines = atoi( argv[i]+1 ); // skip over '-' sign
  else {
   ifstream in( argv[i] );     // try to open the file
   if ( ! in ) cerr << "Unable to open: " << argv[i] << endl;
   else {
    cout << "==> " << argv[i] << " <==\n";
    string line; // used as buffer
    for( int j = 0 ; j < nlines && getline( in, line, '\n' ); j++ )
     cout << line << endl;
   }
  }
}