Fisiere text în C++

File Input/Output in C++

• File input/output (I/O) in C++ involves reading from and writing to files using file streams.
• File streams are objects that represent files and facilitate operations like reading, writing, and appending.
• fstream is the header file needed for file stream operations.

File Streams

• File streams are derived from the stream class and offer functions for file manipulation.
• ifstream for input (reading) from a file.
• ofstream for output (writing) to a file.
• fstream for both input and output (reading and writing) to a file.

Opening a File

• Opening a file involves associating a file stream object with a specific file on the computer's file system.
• Use the open() member function of the file stream object.
• The open() function takes the file name as a string argument.
• Specify the mode in which the file should be opened (e.g., reading, writing, appending).

File Opening Modes

• ios::in: Open for input (reading).
• ios::out: Open for output (writing); if the file exists, it will be overwritten.
• ios::app: Open for output (writing); appends to the end of the file. If the file does not exist, a new file will be created.
• ios::binary: Open in binary mode; important for non-text files (e.g., images).
• ios::ate: Open and position the pointer to end of file. Useful for appending or reading from the end.
• Combining modes: You can combine modes (e.g., ios::out | ios::app).

Creating and Using File Streams

• Creating: Declare a fstream, ifstream, or ofstream object as needed.
• Opening: Use the open() method to associate the object with the file.
• Reading: ifstream supports >> for extracting data from a file to variables.
• Reading line by line: Use getline() to extract entire lines of text.

#include <fstream>
#include <iostream>
#include <string>

int main() {
    std::ifstream inputFile("myFile.txt");

    if (inputFile.is_open()){
        std::string line;
        while (std::getline(inputFile, line)) {
            std::cout << line << std::endl;
        }
        inputFile.close();
    } else {
        std::cerr << "Unable to open file";
    }

    return 0;
}

• Writing: ofstream supports the insertion operator (<<) to write data into files.
• Writing lines: Use << and endl.

#include <fstream>
#include <iostream>
#include <string>

int main() {
    std::ofstream outputFile("myOutputFile.txt");

    if (outputFile.is_open()){
        outputFile << "This is the first line.\n";
        outputFile << "This is the second line.\n";

        outputFile.close();
    } else {
        std::cerr << "Unable to open file";
    }

    return 0;
}

Error Handling

• Always check if the file was opened successfully using is_open().
• Use exception handling (try-catch) or error flags (fail()).
• Close the file using close() when you have finished with it.

Closing Files

• The close() method is crucial for releasing resources and ensuring data is written to disk.

File Positioning

• seekg() and seekp() control the file read/write pointer position.
• Use tellg() or tellp() to get current position.

Important Considerations

• Binary vs. Text Mode: The difference affects how character data is handled; text mode assumes line breaks are encoded as '\n' while binary mode does not.
• Large Files: For huge files and performance, use buffers and avoid unnecessary reads and writes.
• File Existence: Check if a file exists before opening it to prevent errors.
• File Handling in Larger Programs: In larger applications, error handling, robust input validation, and proper resource management are paramount.

Acest quiz abordează conceptul de input/output în C++ folosind fișiere. Vei învăța despre fluxurile de fișiere și modul lor de utilizare pentru citirea și scrierea datelor. De asemenea, se vor discuta modurile de deschidere a fișierelor și utilizarea funcțiilor corecte.