std::filesystem:: is_directory

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C++
Filesystem library
Classes
Functions
File types
Defined in header <filesystem>
bool is_directory ( std:: filesystem :: file_status s ) noexcept ;
(1) (since C++17)
bool is_directory ( const std:: filesystem :: path & p ) ;
(2) (since C++17)
bool is_directory ( const std:: filesystem :: path & p, std:: error_code & ec ) noexcept ;
(3) (since C++17)

Checks if the given file status or path corresponds to a directory.

1) Equivalent to s. type ( ) == file_type :: directory .
2,3) Equivalent to is_directory ( status ( p ) ) or is_directory ( status ( p, ec ) ) , respectively.

Parameters

s - file status to check
p - path to query
ec - error code to modify in case of errors

Return value

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

Exceptions

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

2,3) 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.

Example

Run this code 
#include <cstdio>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.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");
    fs::create_directory("sandbox/dir");
    std::ofstream{"sandbox/file"}; // create regular file
    fs::create_symlink("file", "sandbox/symlink");
 
    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);
 
    // 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 (prefer std::unique_ptr-based custom deleters)
    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

See also

(C++17) (C++17)
determines file attributes
determines file attributes, checking the symlink target
(function)
(C++17)
represents file type and permissions
(class)
(C++17)
checks whether file status is known
(function)
(C++17)
checks whether the given path refers to block device
(function)
(C++17)
checks whether the given path refers to a character device
(function)
(C++17)
checks whether the given path refers to a named pipe
(function)
(C++17)
checks whether the argument refers to an other file
(function)
(C++17)
checks whether the argument refers to a regular file
(function)
(C++17)
checks whether the argument refers to a named IPC socket
(function)
(C++17)
checks whether the argument refers to a symbolic link
(function)
(C++17)
checks whether path refers to existing file system object
(function)
checks whether the directory entry refers to a directory
(public member function of std::filesystem::directory_entry )
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