Copy File

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

int main() {
    string sourceFile = "data.txt";
    string destFile = "data_copy.txt";
    
    // Method 1: Using filesystem (C++17) - Simple
    try {
        copy_file(sourceFile, destFile);
        cout << "File copied successfully using filesystem!" << endl;
    } catch (const filesystem_error& e) {
        cout << "Error: " << e.what() << endl;
    }
    
    // Method 2: Manual copy - Read and write
    ifstream source(sourceFile, ios::binary);
    ofstream dest(destFile + "_manual", ios::binary);
    
    if (source.is_open() && dest.is_open()) {
        dest << source.rdbuf();  // Copy entire file buffer
        
        source.close();
        dest.close();
        
        cout << "File copied manually!" << endl;
    } else {
        cout << "Error opening files for manual copy." << endl;
    }
    
    // Verify copy
    if (exists(destFile)) {
        cout << "\nVerification:" << endl;
        cout << "Source size: " << file_size(sourceFile) << " bytes" << endl;
        cout << "Copy size: " << file_size(destFile) << " bytes" << endl;
        
        if (file_size(sourceFile) == file_size(destFile)) {
            cout << "File sizes match - Copy verified!" << endl;
        }
    }
    
    return 0;
}

File copied successfully using filesystem!
File copied manually!

Verification:
Source size: 156 bytes
Copy size: 156 bytes
File sizes match - Copy verified!

This program teaches you how to Copy a File in C++. File copying duplicates a source file to a destination file, preserving all content. Multiple methods are available, with the filesystem library (C++17) providing the simplest approach.

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1. What This Program Does

The program demonstrates file copying:

• Method 1: Using filesystem::copy_file() (C++17)
• Method 2: Manual copy using read/write
• Using rdbuf() for efficient buffer copying
• Verifying copy by comparing file sizes

File copying enables backup, duplication, and file management.

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2. Header Files Used

1. #include <iostream>

   • Provides cout and cin for input/output operations.

2. #include <fstream>

   • Provides file stream classes (ifstream, ofstream).

3. #include <filesystem>

   • Provides filesystem operations (C++17).

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3. Understanding File Copying

Copy Concept:

• Duplicate source file to destination
• Preserve all content exactly
• Create new file with same data
• Essential for backup and management

Copy Methods:

• filesystem::copy_file(): simple, C++17
• Manual read/write: more control
• rdbuf(): efficient buffer copy
• Binary mode for exact copy

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4. Method 1: Using filesystem::copy_file()

Simple Copy:

copy_file(sourceFile, destFile);

How it works:

• One-line file copy
• Handles all details automatically
• Exception on error
• C++17 required

Error Handling:

try { copy_file(sourceFile, destFile); } catch (const filesystem_error& e) { cout << "Error: " << e.what() << endl; }

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5. Method 2: Manual Copy

Using rdbuf():

ifstream source(sourceFile, ios::binary); ofstream dest(destFile, ios::binary); dest << source.rdbuf();

How it works:

• rdbuf(): copies entire file buffer
• Efficient one-operation copy
• Works with binary mode
• Preserves exact content

Binary Mode:

• ios::binary: exact byte copy
• No text conversion
• Preserves all data
• Recommended for exact copy

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6. Verifying Copy

Comparing File Sizes:

if (file_size(sourceFile) == file_size(destFile)) { cout << "Copy verified!" << endl; }

How it works:

• Compare source and destination sizes
• Same size indicates successful copy
• Can also compare contents
• Verifies copy operation

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7. When to Use Each Method

filesystem::copy_file():

• C++17 available
• Simple one-line copy
• Automatic error handling
• Recommended for new code

Manual Copy:

• More control needed
• Older C++ standards
• Custom copy logic
• Binary file handling

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8. Important Considerations

File Modes:

• Use ios::binary for exact copy
• Preserves all data types
• No text conversion issues
• Essential for binary files

Error Handling:

• Check if source exists
• Handle write permissions
• Verify destination writable
• Provide user feedback

File Overwriting:

• Destination may be overwritten
• Check if destination exists
• Ask user confirmation if needed
• Handle overwrite carefully

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9. return 0;

This ends the program successfully.

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Summary

• File copying: duplicate source file to destination, preserve all content.
• Method 1: filesystem::copy_file() (C++17) - simplest, one-line copy.
• Method 2: Manual copy using rdbuf() - efficient buffer copy.
• Use ios::binary mode for exact byte copy, preserves all data.
• Verify copy by comparing file sizes or contents.
• Understanding file copying enables backup and file management.
• Essential for duplicating files, creating backups, and file operations.

This program is fundamental for learning file management, understanding file duplication, and preparing for backup and file handling operations in C++ programs.