How Can I Accurately Determine a File's Size Using C 's `tellg()` Function?

tellg() Misinterpretation in Estimating File Size

The tellg() function in C is designed to return a token value that represents a specific position within a file. This value can be used to jump back to that position later using the seekg() function. However, it's important to note that tellg() does not directly provide the size of a file in bytes.

In the code provided:

void read_file(const char* name, int *size, char*& buffer) {
  ifstream file;

  file.open(name, ios::in | ios::binary);
  *size = 0;
  if (file.is_open()) {
    // Get length of file
    file.seekg(0, std::ios_base::end);
    int length = *size = file.tellg();
    file.seekg(0, std::ios_base::beg);

    // Allocate buffer in size of file
    buffer = new char[length];

    // Read
    file.read(buffer, length);
    cout <p>The call to file.tellg() is used to estimate the size of the file. However, this approach is incorrect as tellg() does not return the file size directly.</p><p><strong>Correct Approach to Determine File Size</strong></p><p>To accurately determine the size of a file in bytes, it's recommended to use the following approach:</p><pre class="brush:php;toolbar:false">#include <limits>

file.ignore(std::numeric_limits<:streamsize>::max());
std::streamsize length = file.gcount();
file.clear();   // Since ignore will have set eof.
file.seekg(0, std::ios_base::beg);</:streamsize></limits>

This code reads the file until the end, and the gcount() function returns the number of bytes read. This value represents the actual size of the file.

Additional Notes

• The variable buffer should be declared as a char** instead of char* to correctly point to a character array.
• It's advisable to use a std::vector or std::string instead of dynamically allocating memory to simplify memory management and avoid leaks.
• The loop condition in the final print loop should be i

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