std::filesystem::is_fifo(3)

💅 std::filesystem::is_fifo(3) 💅

okay so bestie, welcome to the std::filesystem::is_fifo(3) page from the C++ Standard Libary manual, section 3. (yes, it’s spelled Libary in the source — keeping it exactly, no cap 💅) This is the little function that asks: “is this file a FIFO or pipe file?” and it’s giving very specific C++17 energy. ✨

🌸 NAME 🌸

std::filesystem::is_fifo - std::filesystem::is_fifo

✨ Synopsis ✨

Defined in header <filesystem> — and it’s been here since C++17:

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

and yeah, overload 3 is split like that in the source layout — leaving it as-is, bestie 💅

Checks if the given file status or path corresponds to a FIFO or pipe file, as if determined by POSIX S_ISFIFO. 💖

1. Equivalent to s.type() == file_type::fifo.
2. 2,3) Equivalent to is_fifo(status(p)) or is_fifo(status(p, ec)) respectively.

💖 Parameters 💖

• s — file status to check
• p — path to query
• ec — error code to modify in case of errors

⭐ Return value ⭐

Returns true if the file indicated by p or if the type indicated s refers to a FIFO pipe, false otherwise. The non-throwing overload returns false if an error occurs. 🫶

🔥 Exceptions 🔥

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails. 😭

2,3) 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.

🎀 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

🦋 See also 🦋

• status — determines file attributes (C++17, function)
• symlink_status — determines file attributes, checking the symlink target (C++17, function) — and there’s a floating (C++17) in the source layout right after this one before file_status, so noting it here 🫶
• 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_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_socket — checks whether the argument refers to a named IPC socket (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_fifo — checks whether the directory entry refers to a named pipe (public member function of std::filesystem::directory_entry)

and that’s the whole page, bestie 💖 source/version: http://cppreference.com, dated 2024.06.10. byeee 🫶