std::filesystem::directory_entry::is_block_file
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< cpp | filesystem | directory entry
bool is_block_file()const; | (1) | (since C++17) |
bool is_block_file(std::error_code& ec )constnoexcept; | (2) | (since C++17) |
Checks whether the pointed-to object is a block device. Effectively returns:
1)std::filesystem::is_block_file(status()).
2)std::filesystem::is_block_file(status(ec)).
Contents |
[edit]Parameters
| ec | - | out-parameter for error reporting in the non-throwing overload |
[edit]Return value
true if the referred-to filesystem object is a block device, false otherwise.
[edit]Exceptions
Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.
1) Throws std::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.
2) 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.
[edit]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(conststd::filesystem::directory_entry& 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());conststd::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 filestd::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, [](constint* 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); // Request file system objects status directly:for(constchar* 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")[edit]See also
(C++17) | checks whether the given path refers to block device (function) |
