std::filesystem::directory_entry::is_fifo(3)

NAME
std::filesystem::directory_entry::is_fifo - std::filesystem::directory_entry::is_fifo

Synopsis
   bool is_fifo() const; (since C++17)
   bool is_fifo( std::error_code& ec ) const noexcept;
   Checks whether the pointed-to object is a FIFO or pipe file. Effectively returns
   std::filesystem::is_fifo(status()) or std::filesystem::is_fifo(status(ec)),
   respectively.

Parameters
   ec - out-parameter for error reporting in the non-throwing overload

Return value
   true if the referred-to filesystem object is a FIFO or pipe file, false otherwise.

Exceptions
   The overload that does not take a std::error_code& parameter throws
   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. The overload
   taking a std::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. Any overload not marked
   noexcept may throw std::bad_alloc if memory allocation fails.

Example
// Run this code
 #include <cstdio>
 #include <cstring>
 #include <filesystem>
 #include <fstream>
 #include <functional>
 #include <iostream>
 #include <memory>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/un.h>
 #include <unistd.h>
 namespace fs = std::filesystem;
 void print_entry_type(std::filesystem::directory_entry const& entry) {
     std::cout << entry.path() << ": ";
     if (!entry.exists()) std::cout << "does not exist ";
     if (entry.is_block_file()) std::cout << "is a block device ";
     if (entry.is_character_file()) std::cout << "is a character device ";
     if (entry.is_directory()) std::cout << "is a directory ";
     if (entry.is_fifo()) std::cout << "is a named IPC pipe ";
     if (entry.is_regular_file()) std::cout << "is a regular file ";
     if (entry.is_socket()) std::cout << "is a named IPC socket ";
     if (entry.is_symlink()) std::cout << "(a symlink) ";
     if (entry.is_other()) std::cout << "(an `other` file) ";
     std::cout <<'\n';
 }
 template <typename Type, typename Fun>
 class scoped_cleanup {
     std::unique_ptr<Type, std::function<void(const Type*)>> u;
   public:
     scoped_cleanup(Type* ptr, Fun fun) : u{ptr, std::move(fun)} {}
 };
 int main()
 {
     // create files of different kinds
     std::filesystem::current_path(fs::temp_directory_path());
     const std::filesystem::path sandbox{"sandbox"};
     scoped_cleanup remove_all_at_exit{&sandbox, [](const fs::path* p) {
         std::cout << "cleanup: remove_all(" << *p << ")\n";
         fs::remove_all(*p);
     } };
     std::filesystem::create_directory(sandbox);
     std::ofstream{sandbox/"file"}; // creates a regular file
     std::filesystem::create_directory(sandbox/"dir");
     mkfifo((sandbox/"pipe").string().data(), 0644);
     struct sockaddr_un addr; addr.sun_family = AF_UNIX;
     std::strcpy(addr.sun_path, (sandbox/"sock").string().data());
     int fd {socket(PF_UNIX, SOCK_STREAM, 0)};
     scoped_cleanup close_socket_at_exit{&fd, [](const int* f) {
         std::cout << "cleanup: close socket #" << *f << '\n';
         close(*f);
     } };
     bind(fd, reinterpret_cast<sockaddr*>(std::addressof(addr)), sizeof addr);
     fs::create_symlink("file", sandbox/"symlink");
     for (std::filesystem::directory_entry entry: fs::directory_iterator(sandbox)) {
         print_entry_type(entry);
     }
     // direct calls to status:
     for (const char* str: {"/dev/null", "/dev/cpu", "/usr/include/c++",
                        "/usr/include/asm", "/usr/include/time.h"}) {
         print_entry_type(fs::directory_entry{str});
     }
 } // cleanup via `scoped_cleanup` objects

Possible output:
 "sandbox/symlink": is a regular file (a symlink)
 "sandbox/sock": is a named IPC socket (an `other` file)
 "sandbox/pipe": is a named IPC pipe (an `other` file)
 "sandbox/dir": is a directory
 "sandbox/file": is a regular file
 "/dev/null": is a character device (an `other` file)
 "/dev/cpu": does not exist
 "/usr/include/c++": is a directory
 "/usr/include/asm": is a directory (a symlink)
 "/usr/include/time.h": is a regular file
 cleanup: close socket #3
 cleanup: remove_all("sandbox")

See also
   is_fifo checks whether the given path refers to a named pipe
   (C++17) (function)