std::filesy...try::exists(3)

💅 std::filesystem::directory_entry::exists

okay bestie, welcome to the std::filesystem::directory_entry::exists page — straight out of the C++ Standard Libary manual (yes that's how the manual spells it, we don't gatekeep spelling here 🫶). This is the one that answers the most iconic question of all time: does this thing even exist? 💀

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✨ NAME ✨

std::filesystem::directory_entry::exists — std::filesystem::directory_entry::exists. that's it. that's the whole name. she's her own name twin, main character energy only 👑

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🌸 Synopsis 🌸

bool exists() const;                               (1) (since C++17)
bool exists( std::error_code& ec ) const noexcept; (2) (since C++17)

so what she does: she checks whether the pointed-to object exists ✨. effectively, she returns:

1. std::filesystem::exists(status()),
2. std::filesystem::exists(status(ec)).

⚠️ lowkey important: status() follows symlinks to their targets. so you're not asking "does the link exist", you're asking about the thing it points at. iykyk 🦋

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🎀 Parameters 🎀

• ec — the out-parameter for error reporting in the non-throwing overload. like a little bucket where the error info goes if anything goes wrong 🙈

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⭐ Return value ⭐

true if the referred-to filesystem object exists. 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 😭 (rude, but ok).

1. 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.
2. 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. so like, she cleans up after herself 💅

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🧚 Example 🧚

run this code fr fr:

#include <filesystem>
#include <iostream>

int main()
{
    for (auto const str:
    {
        "/usr/bin/cat",
        "/usr/bin/mouse",
        "/usr/bin/python",
        "/usr/bin/bison",
        "/usr/bin/yacc",
        "/usr/bin/c++",
    })
    {
        std::filesystem::directory_entry entry{str};

        std::cout << "directory entry " << entry
                  << (entry.exists() ? " exists\n" : " does not exist\n");
    }
}

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🌈 Possible output 🌈

output on a POSIX system, bestie:

directory entry "/usr/bin/cat" exist
directory entry "/usr/bin/mouse" does not exist
directory entry "/usr/bin/python" exists
directory entry "/usr/bin/bison" exists
directory entry "/usr/bin/yacc" does not exist
directory entry "/usr/bin/c++" exists

(not me noticing the first line says exist and the rest say exists 😭 that's literally in the original, i don't make the rules 💀)

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🦋 See also 🦋

• exists — checks whether path refers to existing file system object (C++17) (function) ✨

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okay pookie that's the whole page, you ate that 🫶 go forth and check if things exist 💖

source: http://cppreference.com · version date: 2024.06.10 · this was std::filesy...try::exists(3) — mwah, bye bestie 👋💅