C++ File handling: Merge multiple text files

Last update on December 20 2024 12:22:54 (UTC/GMT +8 hours)

Write a C++ program to merge multiple text files into a single file.

Sample Solution:

C Code:

#include <iostream>   // Including the input/output stream library
#include <fstream>    // Including the file stream library
#include <string>     // Including the string handling library
#include <vector>     // Including the vector container

// Function to display the content of a file
void displayFileContent(const std::string & filename) {
  std::ifstream file(filename); // Open file with given filename for reading
  std::string line; // Declare a string to store each line of text

  if (file.is_open()) { // Check if the file was successfully opened
    std::cout << "File content:" << std::endl; // Displaying a message indicating file content
    while (std::getline(file, line)) { // Read each line from the file
      std::cout << line << std::endl; // Display each line of the file
    }
    file.close(); // Close the file
  } else {
    std::cout << "Failed to open the file." << std::endl; // Display an error message if file opening failed
  }
}

int main() {
  std::vector<std::string> inputFiles = { // List of input files
    "test1.txt",
    "test2.txt",
    "test3.txt",
    "test4.txt"
  };
  std::cout << "Content of test1.txt, test2.txt, test3.txt, text4.txt: " << std::endl;

  displayFileContent("test1.txt"); // Display content of "test1.txt"
  displayFileContent("test2.txt"); // Display content of "test2.txt"
  displayFileContent("test3.txt"); // Display content of "test3.txt"
  displayFileContent("test4.txt"); // Display content of "test4.txt"

  std::string outputFile = "merged_test_file.txt"; // Output file

  std::ofstream mergedFile(outputFile); // Create or overwrite the output file named "merged_test_file.txt" for writing

  if (mergedFile.is_open()) { // Check if the output file was successfully opened
    for (const auto & inputFile: inputFiles) { // Iterate through each input file
      std::ifstream inputFileStream(inputFile); // Open each input file for reading

      if (inputFileStream.is_open()) { // Check if the input file was successfully opened
        std::string line; // Declare a string to store each line of text

        while (std::getline(inputFileStream, line)) { // Read each line from the input file
          mergedFile << line << "\n"; // Write each line to the merged file
        }

        inputFileStream.close(); // Close the input file
      } else {
        std::cout << "Failed to open input file: " << inputFile << std::endl; // Display an error message if file opening failed
      }
    }

    mergedFile.close(); // Close the merged file
    std::cout << "\nFiles merged successfully." << std::endl; // Display a success message
    std::cout << "\nContent of the merged file:" << std::endl;
    displayFileContent("merged_test_file.txt"); // Display content of "merged_test_file.txt"
  } else {
    std::cout << "Failed to open the output file." << std::endl; // Display an error message if output file opening failed
  }

  return 0; // Return 0 to indicate successful execution
}

Sample Output:

Content of test1.txt, test2.txt, test3.txt, text4.txt:
File content:
Many vendors provide C++ compilers, including the Free Software Foundation, LLVM, Microsoft, Intel, Embarcadero, Oracle, and IBM.
File content:
C++ is a high-level, general-purpose programming language created by Danish computer scientist Bjarne Stroustrup.
File content:
It is almost always implemented in a compiled language.
File content:
Modern C++ currently has object-oriented, generic, and functional features, in addition to facilities for low-level memory manipulation.
First released in 1985 as an extension of the C programming language, it has since expanded significantly over time.

Files merged successfully.

Content of the merged file:
File content:
Many vendors provide C++ compilers, including the Free Software Foundation, LLVM, Microsoft, Intel, Embarcadero, Oracle, and IBM.
C++ is a high-level, general-purpose programming language created by Danish computer scientist Bjarne Stroustrup.
It is almost always implemented in a compiled language.
Modern C++ currently has object-oriented, generic, and functional features, in addition to facilities for low-level memory manipulation.
First released in 1985 as an extension of the C programming language, it has since expanded significantly over time.

Explanation:

In the above exercise,

• Define a vector inputFiles that contains the names of the input files to be merged.
• Specify the output file name as a string outputFile.
• The program uses an output file stream mergedFile to create or overwrite the output file.
• Iterate over each input file in the inputFiles vector.
• For each input file, open it using an input file stream inputFileStream.
• If the input file is successfully opened, read each line from the input file using std::getline() and write it to the merged file using the output file stream mergedFile.
• After merging all the files, close the merged file and display a success message.

Flowchart:

CPP Code Editor:

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