std::filesystem::is_socket(3)

💖 std::filesystem::is_socket(3) — C++ Standard Library 💖

okay so bestie, welcome to the C++ Standard Library manual page for std::filesystem::is_socket(3) — and yes, this is literally the function that checks whether something is a named IPC socket. iconic behavior only. 🧚✨

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🌸 NAME 🌸

std::filesystem::is_socket — std::filesystem::is_socket

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🎀 Synopsis 🎀

Defined in header <filesystem>:

   Defined in header <filesystem>
   bool is_socket( std::filesystem::file_status s ) noexcept;
(1) (since C++17)
   bool is_socket( const std::filesystem::path& p );
(2) (since C++17)
   bool is_socket( const std::filesystem::path& p, std::error_code&
(3) (since C++17)
ec ) noexcept;

So what does it do? It checks if the given file status or path corresponds to a named IPC socket, as if determined by the POSIX S_IFSOCK. 💅

• Overload (1) is equivalent to s.type() == file_type::socket.
• Overloads (2) and (3) are equivalent to is_socket(status(p)) or is_socket(status(p, ec)).

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🦋 Parameters 🦋

• s — file status to check, bestie.
• p — path to examine. go look at it, queen.
• ec — out-parameter for error reporting in the non-throwing overload. it catches the messy stuff so you don't have to 😭

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🌈 Return value 🌈

returns true if the file indicated by p or if the type indicated by s refers to a named socket.

the non-throwing overload returns false if an error occurs. no drama, just false. 💅

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🔥 Exceptions 🔥

any overload not marked noexcept may throw std::bad_alloc if memory allocation fails. rude, but okay.

for overloads 2 and 3: they set a std::error_code& parameter to the OS API error code if an OS API call fails, and execute ec.clear() if no errors occur. very "i handle my own problems" energy. ✨

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💜 Notes 💜

Named sockets are UNIX domain sockets constructed with socket and bind POSIX APIs, which may be used for advanced interprocess communication. in particular, they may be used to transport open file descriptors from one running process to another. that's giving main character IPC energy, no cap. 🫶

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🍓 Example 🍓

// Run this code

#include <cstdio>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.h>

namespace fs = std::filesystem;

void demo_status(const fs::path& p, fs::file_status s)
{
    std::cout << p;
    // alternative: switch(s.type()) { case fs::file_type::regular: ...}
    if (fs::is_regular_file(s))
        std::cout << " is a regular file\n";
    if (fs::is_directory(s))
        std::cout << " is a directory\n";
    if (fs::is_block_file(s))
        std::cout << " is a block device\n";
    if (fs::is_character_file(s))
        std::cout << " is a character device\n";
    if (fs::is_fifo(s))
        std::cout << " is a named IPC pipe\n";
    if (fs::is_socket(s))
        std::cout << " is a named IPC socket\n";
    if (fs::is_symlink(s))
        std::cout << " is a symlink\n";
    if (!fs::exists(s))
        std::cout << " does not exist\n";
}

int main()
{
    // create files of different kinds
    fs::create_directory("sandbox");
    fs::create_directory("sandbox/dir");
    std::ofstream{"sandbox/file"}; // create regular file
    fs::create_symlink("file", "sandbox/symlink");

    mkfifo("sandbox/pipe", 0644);
    sockaddr_un addr;
    addr.sun_family = AF_UNIX;
    std::strcpy(addr.sun_path, "sandbox/sock");
    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
    bind(fd, reinterpret_cast<sockaddr*>(&addr), sizeof addr);

    // demo different status accessors
    for (auto it{fs::directory_iterator("sandbox")}; it !=
fs::directory_iterator(); ++it)
        demo_status(*it, it->symlink_status()); // use cached status
from directory entry
    demo_status("/dev/null", fs::status("/dev/null")); // direct calls
to status
    demo_status("/dev/sda", fs::status("/dev/sda"));
    demo_status("sandbox/no", fs::status("/sandbox/no"));

    // cleanup (prefer std::unique_ptr-based custom deleters)
    close(fd);
    fs::remove_all("sandbox");
}

⭐ Possible output ⭐

"sandbox/file" is a regular file
"sandbox/dir" is a directory
"sandbox/pipe" is a named IPC pipe
"sandbox/sock" is a named IPC socket
"sandbox/symlink" is a symlink
"/dev/null" is a character device
"/dev/sda" is a block device
"sandbox/no" does not exist

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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)
• status_known — checks whether file status is known (C++17) (function)
• is_block_file — checks whether the given path refers to block device (C++17) (function)
• is_character_file — checks whether the given path refers to a character device (C++17) (function)
• is_directory — checks whether the given path refers to a directory (C++17) (function)
• is_fifo — checks whether the given path refers to a named pipe (C++17) (function)
• is_other — checks whether the argument refers to an other file (C++17) (function)
• is_regular_file — checks whether the argument refers to a regular file (C++17) (function)
• is_symlink — checks whether the argument refers to a symbolic link (C++17) (function)
• exists — checks whether path refers to existing file system object (C++17) (function)
• is_socket — checks whether the directory entry refers to a named IPC socket (public member function of std::filesystem::directory_entry)

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that's the whole vibe, bestie. page sourced from http://cppreference.com, version/date 2024.06.10. now go check ur sockets and slay 💅✨🦋