std::filesystem::exists(3)

💖 std::filesystem::exists(3) 💖

okay bestie, welcome to the C++ Standard Libary page for std::filesystem::exists — yes, “Libary,” that’s literally the manual name up top, and we are keeping it because it’s iconic 💅.

This one is literally checking if your path or file status points at something that exists — file or directory, no cap.

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🌸 NAME 🌸

std::filesystem::exists — std::filesystem::exists

like… that’s the whole NAME section. it’s just the function name doing a little mirror selfie. periodt.

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📜 Synopsis 📜

It’s defined in header <filesystem> ✨

bool exists( std::filesystem::file_status s ) noexcept;
(1) (since C++17)
bool exists( const std::filesystem::path& p );
(2) (since C++17)
bool exists( const std::filesystem::path& p, std::error_code& ec )
(3) (since C++17)
noexcept;

Checks if the given file status or path corresponds to an existing file or directory.

• 1) Equivalent to status_known(s) && s.type() != file_type::not_found.
• 2,3) Let s be a std::filesystem::file_status determined as if by status(p) or status(p, ec) (symlinks are followed), respectively. Returns exists(s). The non-throwing overload calls ec.clear() if status_known(s).

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🎀 Parameters 🎀

• s — file status to check
• p — path to examine
• ec — out-parameter for error reporting in the non-throwing overload

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✅ Return value ✅

true if the given path or file status corresponds to an existing file or directory, false otherwise.

like, that’s it. that’s the vibe check. 🫶

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😭 Exceptions 😭

• Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.
• 2) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with p as the first path argument and the OS error code as the error code argument.
• 3) Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur.

🚨 No filesystem exception is thrown if the object does not exist — use the return value, bestie. don’t be dramatic about it.

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🧚 Notes 🧚

The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling exists(*iterator) is less efficient than exists(iterator->status()).

so like… if you already have the status cached from the directory entry, use that. your future self will thank you 💖

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🖥️ Example 🖥️

// Run this code

#include <cstdint>
#include <filesystem>
#include <fstream>
#include <iostream>
namespace fs = std::filesystem;

void demo_exists(const fs::path& p, fs::file_status s =
fs::file_status{})
{
    std::cout << p;
    if (fs::status_known(s) ? fs::exists(s) : fs::exists(p))
        std::cout << " exists\n";
    else
        std::cout << " does not exist\n";
}

int main()
{
    const fs::path sandbox{"sandbox"};
    fs::create_directory(sandbox);
    std::ofstream{sandbox/"file"}; // create regular file
    fs::create_symlink("non-existing", sandbox/"symlink");

    demo_exists(sandbox);

    for (const auto& entry : fs::directory_iterator(sandbox))
        demo_exists(entry, entry.status()); // use cached status from
directory entry

    fs::remove_all(sandbox);
}

✨ Output ✨

"sandbox" exists
"sandbox/symlink" does not exist
"sandbox/file" exists

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👀 See also 👀

• status — determines file attributes; (C++17); (function)
• symlink_status — determines file attributes, checking the symlink target; (C++17); (function)
• file_status — represents file type and permissions; (C++17); (class)
• exists — checks whether directory entry refers to existing file system object; public member function of std::filesystem::directory_entry

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okay that’s the whole page, bestie 💖 source: http://cppreference.com · version/date: 2024.06.10 · page: std::filesystem::exists(3) — now go check if your file exists and slay ✨