std::filesystem::equivalent

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

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Numerics library

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Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::system_complete filesystem::canonical filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path filesystem::exists filesystem::equivalent	filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

Defined in header <filesystem>
bool equivalent( const std::filesystem::path& p1,                  const std::filesystem::path& p2 ); bool equivalent( const std::filesystem::path& p1,                  const std::filesystem::path& p2,                  std::error_code& ec );	(1)	(since C++17)

Checks whether the paths p1 and p2 refer to the same file or directory and have the same file status as determined by status (symlinks are followed).

If p1 or p2 does not exist or if their file type is not file, directory, or symlink (as determined by is_other), an error is reported.

The non-throwing overload returns false on errors.

Parameters

p1, p2	-	paths to check for equivalence
ec	-	out-parameter for error reporting in the non-throwing overload

Return value

true if the p1 and p2 refer to the same file or directory and their file status is the same. false otherwise.

Exceptions

The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p1 as the first argument, p2 as the second 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

  

Notes

Two paths are considered to resolve to the same file system entity if st_dev and st_ino of their POSIX stat structure, obtained as if by POSIX stat, are equal. (meaning, the files are locate on the same device at the same location)

In particular, all hard links for the same file or directory are equivalent, and a symlink and its target on the same file system are equivalent.

Example

Run this code

#include <iostream>
#include <cstdint>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    // hard link equivalency
    fs::path p1 = ".";
    fs::path p2 = fs::current_path();
    if(fs::equivalent(p1, p2))
        std::cout << p1 << " is equivalent to " << p2 << '\n';
 
    // symlink equivalency
    fs::path p3 = "/lib/libc.so.6";
    fs::path p4 = p3.parent_path() / fs::read_symlink(p3);
    if(fs::equivalent(p3, p4))
        std::cout << p3 << " is equivalent to " << p4 << '\n';
}

Possible output:

"." is equivalent to "/var/tmp/test"
"/lib/libc.so.6" is equivalent to "/lib/libc-2.12.so"

See also

statussymlink_status (C++17)(C++17)	determines file attributes determines file attributes, checking the symlink target (function)