Checking if a File Exists

To check if a file exists before trying to open it in C++, you can use the <filesystem> library, which provides a straightforward way to handle filesystem operations.

The function std::filesystem::exists() can be used to check if a file exists. Here's an example of how to use it:

1#include <filesystem>
2#include <iostream>
3
4int main() {
5  std::filesystem::path filePath{R"(c:\test\file.txt)"};
6
7  if (std::filesystem::exists(filePath)) {
8    std::cout << "The file exists.\n";
9  } else {
10    std::cout << "The file does not exist.\n";
11  }
12}

1The file does not exist.

In this example, we include the <filesystem> header and create a std::filesystem::path object with the path to the file we want to check. We then use std::filesystem::exists() to determine if the file exists. The function returns a boolean value: true if the file exists, and false otherwise.

Using this approach is beneficial because it allows your program to handle situations where the file might not be present, thus preventing runtime errors that could occur when trying to open a non-existent file. This is particularly useful in scenarios where the file's presence cannot be guaranteed, such as reading user-generated files or accessing files on a network.

By incorporating std::filesystem::exists() into your file handling logic, you can create more robust and error-resistant applications. This method is part of the C++17 standard, so ensure your compiler supports C++17 or later.

If you need more advanced file handling, like checking permissions or differentiating between files and directories, std::filesystem provides additional functions like is_regular_file() and status() that can be very helpful.