文本文件读写（1.5.1 文件输入和输出）？

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
ofstream outfile( "out_file.txt" );
ifstream infile( "in_file.txt" );
if ( ! infile ) {
cerr << "error: unable to open input file!\n";
return -1;
}
if ( ! outfile ) {
cerr << "error: unable to open output file!\n";
return -2;
}
string word;
while ( infile >> word )
outfile << word << ' ';

return 0;
}