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

From cppreference.com
 
 
 
Defined in header <filesystem>
std::filesystem::file_status status(const std::filesystem::path& p)

std::filesystem::file_status status(const std::filesystem::path& p,

                                    std::error_code& ec)
(1) (since C++17)
std::filesystem::file_status symlink_status(const std::filesystem::path& p)

std::filesystem::file_status symlink_status(const std::filesystem::path& p,

                                            std::error_code& ec)
(2) (since C++17)
1) Determines the type and attributes of the filesystem object identified by p as if by POSIX stat (symlinks are followed to their targets). In the following description, prms is the result of (m & perms::mask), where m is obtained as if by taking st_mode from the POSIX struct stat and converting it to the type std::filesystem::perms.
  • If p is a regular file (as if by POSIX S_ISREG), returns file_status(file_type::regular, prms).
  • If p is a directory (as if by POSIX S_ISDIR), returns file_status(file_type::directory, prms)
  • If p is a block special file (as if by POSIX S_ISBLK), returns file_status(file_type::block, prms)
  • If p is a character special file (as if by POSIX S_ISCHR), returns file_status(file_type::character, prms)
  • If p is a fifo or pipe file (as if by POSIX S_ISFIFO), returns file_status(file_type::fifo, prms)
  • If p is a socket (as if by POSIX S_ISSOCK), returns file_status(file_type::socket, prms)
  • If p has an implementation-defined file type, returns file_status(file_type::A, prms) where A is the implementation-defined file_type constant for that type.
  • If p does not exist, returns file_status(file_type::not_found)
  • If p exists but file attributes cannot be determined, e.g. due to lack of permissions, returns file_status(file_type::unknown)
  • If errors prevent even knowing whether p exists, the non-throwing overload sets ec and returns file_status(file_type::none), and the throwing overload throws filesystem_error
  • Otherwise, returns file_status(file_type::unknown, prms)
2) Same as (1) except that the behavior is as if the POSIX lstat is used (symlinks are not followed):
  • If p is a symlink, returns file_status(file_type::symlink)

Contents

[edit] Parameters

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

[edit] Return value

The file status (a file_status object)

[edit] 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 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.

[edit] Notes

The information provided by this function is usually also provided as a byproduct of directory iteration, and may be obtained by the member functions of directory_entry. During directory iteration, calling status again is unnecessary.

[edit] 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

[edit] See also

represents file type and permissions
(class) [edit]
checks whether file status is known
(function) [edit]
checks whether the given path refers to block device
(function) [edit]
checks whether the given path refers to a character device
(function) [edit]
checks whether the given path refers to a directory
(function) [edit]
(C++17)
checks whether the given path refers to a named pipe
(function) [edit]
(C++17)
checks whether the argument refers to an other file
(function) [edit]
checks whether the argument refers to a regular file
(function) [edit]
(C++17)
checks whether the argument refers to a named IPC socket
(function) [edit]
checks whether the argument refers to a symbolic link
(function) [edit]
(C++17)
checks whether path refers to existing file system object
(function) [edit]
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]