# std::filesystem::equivalent

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< cpp‎ | filesystem

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 ) noexcept; | (1) | (since C++17)

Checks whether the paths `p1` and `p2` resolve to the same file system entity.

If either `p1` or `p2` does not exist, 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 path argument, `p2` as the second 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

Two paths are considered to resolve to the same file system entity if the two candidate entities the paths resolve to are located on the same device at the same location. For POSIX, this means that the `st_dev` and `st_ino` members of their POSIX stat structure, obtained as if by POSIX stat, are equal.

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.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 2937 | C++17 | error condition specified incorrectly | corrected

### 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

status symlink_status (C++17)(C++17) | determines file attributes determines file attributes, checking the symlink target (function)

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