Simple File-Comparison Utility - C++ File Stream

C++ examples for File Stream:File Operation

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Description

Simple File-Comparison Utility

Demo Code

#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char *argv[])
{
   bool equal = true;
   bool ferr = false;
   unsigned char buf1[1024], buf2[1024];
   if(argc!=3) {//w w w  . j  ava 2 s.c  om
      cout << "Usage: compfiles <file1> <file2>\n";
      return 1;
   }
   // Open both files for binary operations.
   ifstream f1(argv[1], ios::in | ios::binary);
   if(!f1) {
      cout << "Cannot open " << argv[1] << endl;
      return 1;
   }
   ifstream f2(argv[2], ios::in | ios::binary);
   if(!f2) {
      cout << "Cannot open " << argv[2] << endl;
      f1.close();
      if(!f1.good())
         cout << "Error closing " << argv[1] << endl;
      return 1;
   }
   cout << "Comparing files...\n";
   do {
      // Read a buffer full of data from both files.
      f1.read((char *) buf1, sizeof buf1);
      f2.read((char *) buf2, sizeof buf2);
      // Check for read errors.
      if(!f1.eof() && !f1.good()) {
         cout << "Error reading " << argv[1] << endl;
         ferr = true;
         break;
      }
      if(!f2.eof() && !f2.good()) {
         cout << "Error reading " << argv[2] << endl;
         ferr = true;
         break;
      }
      // If the two files differ in length, then at the
      // end of the file, the gcounts will be different.
      if(f1.gcount() != f2.gcount()) {
         cout << "Files are different lengths.\n";
         equal = false;
         break;
      }
      // Compare contents of buffers.
      for(int i=0; i < f1.gcount(); ++i)
      if(buf1[i] != buf2[i]) {
         cout << "Files differ.\n";
         equal = false;
         break;
      }
   } while(!f1.eof() && !f2.eof() && equal);
   if(!ferr && equal) cout << "Files are the same.\n";
   // Clear eofbit, and possibly error bits.
   f1.clear();
   f2.clear();
   f1.close();
   f2.close();
   if(!f1.good() || !f2.good()) {
      cout << "Error closing files.\n";
      return 1;
   }
   return 0;
}

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