std::filesystem::directory_entry::is_block_file
From cppreference.com
< cpp | filesystem | directory entry
| bool is_block_file() const; bool is_block_file( std::error_code& ec ) const noexcept; |
(since C++17) | |
Checks whether the pointed-to object is a block device. Effectively returns std::filesystem::is_block_file(status()) or std::filesystem::is_block_file(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 block device, 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
| (C++17) |
checks whether the given path refers to block device (function) |