##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::filesystem::is_block_file

From cppreference.com
< cpp‎ | filesystem

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

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)).

### [edit] Parameters

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

### [edit] 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.

### [edit] Exceptions

1)
`noexcept` specification:
noexcept
2,3) The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed with `p` as the first argument and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. 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. This overload has
`noexcept` specification:
noexcept

### [edit] Example

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
        fs::create_directory("sandbox");
        std::ofstream("sandbox/file"); // create regular file
        fs::create_directory("sandbox/dir");
        mkfifo("sandbox/pipe", 0644);
        struct 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, (struct 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
        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

### [edit] See also

status symlink_status (C++17)(C++17) | determines file attributes determines file attributes, checking the symlink target (function) [edit]
file_status (C++17) | represents file type and permissions (class) [edit]
status_known (C++17) | checks whether file status is known (function) [edit]
is_character_file (C++17) | checks whether the given path refers to a character device (function) [edit]
is_directory (C++17) | checks whether the given path refers to a directory (function) [edit]
is_fifo (C++17) | checks whether the given path refers to a named pipe (function) [edit]
is_other (C++17) | checks whether the argument refers to an other file (function) [edit]
is_regular_file (C++17) | checks whether the argument refers to a regular file (function) [edit]
is_socket (C++17) | checks whether the argument refers to a named IPC socket (function) [edit]
is_symlink (C++17) | checks whether the argument refers to a symbolic link (function) [edit]
exists (C++17) | checks whether path refers to existing file system object (function) [edit]
status symlink_status | status of the file designated by this directory entry symlink_status of the file designated by this directory entry (public member function of `std::filesystem::directory_entry`) [edit]

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/filesystem/is_block_file&oldid=91727"
Category:

- unconditionally noexcept

Hidden categories:

- Pages with unreviewed unconditional noexcept template
- Pages with unreviewed noexcept template