Relative Paths Between Absolute Paths

How do I find the relative path between two absolute paths?

To find the relative path between two absolute paths in C++, you can use the std::filesystem::relative() function.

This function computes the relative path from one absolute path to another. Here's how you can do it:

#include <filesystem>
#include <iostream>

int main() {
  std::filesystem::path base{
    R"(C:\Users\example\projects)"};
  std::filesystem::path target{
    R"(C:\Users\example\projects\subdir\file.txt)"};

  std::filesystem::path relativePath =
    std::filesystem::relative(target, base);
  std::cout << "Relative Path: "
    << relativePath.string();
}
Relative Path: subdir\file.txt

Key Points

  1. Base Path: The starting point from which you want to calculate the relative path.
  2. Target Path: The destination path you want to reach relative to the base path.
  3. Function: Use std::filesystem::relative(target, base) to compute the relative path.

Understanding Relative Paths

Relative paths are crucial when you want to specify paths relative to a certain directory, especially in projects that may be moved between different environments. This makes your code more flexible and portable.

Handling Different Platforms

std::filesystem::relative() handles platform-specific path separators, making it a robust solution for cross-platform applications. Whether you're working on Windows with backslashes (\) or on Unix-like systems with forward slashes (/), the function ensures the correct path format.

Error Handling

Ensure both paths are absolute. If you pass relative paths to std::filesystem::relative(), it will throw an error. Here's how to handle it:

#include <filesystem>
#include <iostream>

namespace fs = std::filesystem;

int main() {
  fs::path base{
    R"(C:\Users\example\projects)"};
  fs::path target{
    R"(C:\Users\example\projects\subdir\file.txt)"};

  try {
    fs::path relativePath =
      fs::relative(target, base);
    std::cout << "Relative Path: "
      << relativePath.string();
  } catch (const fs::filesystem_error& e) {
    std::cerr << "Error: " << e.what();
  }
}
Relative Path: subdir\file.txt

Conclusion

Finding the relative path between two absolute paths using std::filesystem::relative() is straightforward and ensures your paths remain flexible and portable. Always handle exceptions to manage any potential errors gracefully.

File System Paths

A guide to effectively working with file system paths, using the std::filesystem::path type.

Questions & Answers

Answers are generated by AI models and may not have been reviewed. Be mindful when running any code on your device.

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