std::experi...::is_socket(3)

💅 std::experimental::filesystem::is_socket

okay so bestie, this is a manual page for std::experimental::filesystem::is_socket — it's from the C++ Standard Library, specifically the filesystem TS (Technical Specification, iykyk). It's giving "niche but iconic" energy. ✨

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✨ NAME ✨

std::experimental::filesystem::is_socket — the function that checks if your file path or file status is giving named IPC socket vibes 🧦🦋

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🌸 SYNOPSIS 🌸

Defined in header <experimental/filesystem>:

bool is_socket( file_status s );                 (1) (filesystem TS)
bool is_socket( const path& p );                 (2) (filesystem TS)
bool is_socket( const path& p, error_code& ec );

So what's the vibe check here? This function checks if the given file status or path corresponds to a named IPC socket, as if determined by the POSIX S_IFSOCK macro. No cap, that's literally what it does. 💅

1. Equivalent to s.type() == file_type::socket. Simple slay.
2. Equivalent to is_socket(status(p)) or is_socket(status(p, ec)). Either way, same energy.

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🎀 PARAMETERS 🎀

• s — file status to check, bestie. Like, what type is this file even?
• p — path to examine. The one you're curious about.
• ec — out-parameter for error reporting in the non-throwing overload. It's the "if something goes wrong, put the tea here" slot. 🙈

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👑 RETURN VALUE 👑

true if the file indicated by p or if the type indicated by s refers to a named socket. Iconic behavior, honestly.

The non-throwing overload returns false if an error occurs. So if something goes wrong, it just says "nah" instead of throwing hands. 💀

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🔥 EXCEPTIONS 🔥

Overload 1 (the file_status one):

noexcept specification: noexcept

So it literally promises not to throw. Periodt. 💅

Overload 2 (the const path& one that doesn't take an error_code&):

• Throws filesystem_error on underlying OS API errors, constructed with p as the first argument and the OS error code as the error code argument. It's giving "the system said no and here's the receipts." 😭
• std::bad_alloc may be thrown if memory allocation fails. Classic memory drama.
• The overload taking an error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. So it's like, "here's your error or here's your clean slate, bestie."
• This overload has noexcept specification: noexcept

So lowkey, the version with ec is the safer bet if you don't want exceptions flying around. iykyk. 🦋

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🌈 NOTES 🌈

Named sockets are UNIX domain sockets constructed with socket and bind POSIX APIs. They may be used for advanced interprocess communication. In particular, they may be used to transport open file descriptors from one running process to another. It's giving "main character energy" for IPC, fr fr. 🎀

The information provided by this function is usually also provided as a byproduct of directory iteration. So during directory iteration, calling is_socket(*iterator) is less efficient than is_socket(iterator->status()). Bestie, use the cached status. It's literally right there. Don't do extra work for no reason. 🫶

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⭐ EXAMPLE ⭐

okay this example is actually so cute, look:

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

namespace fs = std::experimental::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");
    std::ofstream("sandbox/file"); // create regular file
    fs::create_directory("sandbox/dir");
    mkfifo("sandbox/pipe", 0644);
    struct 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, (struct sockaddr*)&addr, sizeof addr);
    fs::create_symlink("file", "sandbox/symlink");

    // 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
    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

Look at that output slaying! It's literally identifying every file type in the sandbox. Obsessed. 💖

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🌸 SEE ALSO 🌸

• status — determines file attributes. The OG.
• symlink_status — determines file attributes, checking the symlink target. (function)
• file_status — represents file type and permissions. (class)
• status_known — checks whether file status is known. (function)
• is_block_file — checks whether the given path refers to block device. (function)
• is_character_file — checks whether the given path refers to a character device. (function)
• is_directory — checks whether the given path refers to a directory. (function)
• is_fifo — checks whether the given path refers to a named pipe. (function)
• is_other — checks whether the argument refers to an other file. (function)
• is_regular_file — checks whether the argument refers to a regular file. (function)
• is_symlink — checks whether the argument refers to a symbolic link. (function)
• exists — checks whether path refers to existing file system object. (function)
• status — cached status of the file designated by this directory entry. (public member function of std::experimental::filesystem::directory_entry)
• symlink_status — cached symlink_status of the file designated by this directory entry. (public member function of std::experimental::filesystem::directory_entry)

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Categories: Noindexed pages, unconditionally noexcept

Hidden categories: Pages with unreviewed unconditional noexcept template, Pages with unreviewed noexcept template

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anyway bestie, that's the whole tea ☕ — this page came from http://cppreference.com, date 2024.06.10, and the manpage title is std::experi...::is_socket(3). Now go forth and check your sockets with confidence! 💅✨🦋🎀