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std::filesystem::is_block_file(3) C++ Standard Libary std::filesystem::is_block_file(3)


std::filesystem::is_block_file - std::filesystem::is_block_file


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

Checks if the given file status or path corresponds to a block special file, as if
determined by the POSIX S_ISBLK. Examples of block special files are block devices
such as /dev/sda or /dev/loop0 on Linux.

1) Equivalent to s.type() == file_type::block.
2) Equivalent to is_block_file(status(p)) or is_block_file(status(p, ec)).


s - file status to check
p - path to examine
ec - out-parameter for error reporting in the non-throwing overload

Return value

true if the file indicated by p or if the type indicated s refers to a block device.
The non-throwing overload returns false if an error occurs.


2) 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.


// Run this code

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cstring>
#include <filesystem>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.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
std::ofstream("sandbox/file"); // create regular file
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);
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

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
symlink_status determines file attributes, checking the symlink target
(C++17) (function)
file_status represents file type and permissions
(C++17) (class)
status_known checks whether file status is known
(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_fifo checks whether the given path refers to a named pipe
(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_block_file checks whether the directory entry refers to block device
(public member function of std::filesystem::directory_entry)