W3cubDocs

/C++

std::filesystem::directory_entry::status, std::filesystem::directory_entry::symlink_status

std::filesystem::file_status status() const;
std::filesystem::file_status status( std::error_code& ec ) const noexcept;

(1)

(since C++17)

std::filesystem::file_status symlink_status() const;
std::filesystem::file_status symlink_status( std::error_code& ec ) const noexcept;

(2)

(since C++17)

1) Returns status of the entry, as if determined by a status call (symlinks are followed to their targets)

2) Returns status of the entry, as if determined by a symlink_status call (symlinks are not followed)

Parameters

out-parameter for error reporting in the non-throwing overload

Return value

The status of the file referred to by the entry.

Exceptions

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 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.

Notes

Many low-level OS APIs for directory traversal retrieve file attributes along with the next directory entry. The constructors and the non-const member functions of directory_iterator store these attributes, if any, in the pointed-to directory_entry without calling directory_entry::refresh, which makes it possible to examine the attributes of the directory entries as they are being iterated over, without making additional system calls.

Example

#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

refresh	updates the cached file attributes (public member function)
exists	checks whether directory entry refers to existing file system object (public member function)
is_block_file	checks whether the directory entry refers to block device (public member function)
is_character_file	checks whether the directory entry refers to a character device (public member function)
is_directory	checks whether the directory entry refers to a directory (public member function)
is_fifo	checks whether the directory entry refers to a named pipe (public member function)
is_other	checks whether the directory entry refers to an other file (public member function)
is_regular_file	checks whether the directory entry refers to a regular file (public member function)
is_socket	checks whether the directory entry refers to a named IPC socket (public member function)
is_symlink	checks whether the directory entry refers to a symbolic link (public member function)
file_size	returns the size of the file to which the directory entry refers (public member function)
hard_link_count	returns the number of hard links referring to the file to which the directory entry refers (public member function)
last_write_time	gets or sets the time of the last data modification of the file to which the directory entry refers (public member function)