# std::experimental::filesystem::canonical

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< cpp‎ | experimental‎ | fs

Defined in header `<experimental/filesystem>` |  |
path canonical( const path& p, const path& base = current_path() ); | (1) | (filesystem TS)
path canonical( const path& p, error_code& ec ); | (2) | (filesystem TS)
path canonical( const path& p, const path& base, error_code& ec ); | (3) | (filesystem TS)

Converts path `p` to a canonical absolute path, i.e. an absolute path that has no dot, dot-dot elements or symbolic links.

If `p` is not an absolute path, the function behaves as if it is first made absolute by absolute(p, base) or absolute(p) for (2)

The path `p` must exist.

### Parameters

p | - | a path which may be absolute or relative to `base`, and which must be an existing path
base | - | base path to be used in case `p` is relative
ec | - | error code to store error status to

### Return value

An absolute path that resolves to the same file as absolute(p, base) (or absolute(p) for (2)).

### Exceptions

The overload that does not take a `error_code&` parameter throws filesystem_error on underlying OS API errors, constructed with `p` as the first argument, `base` 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 `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

This function is modeled after the POSIX realpath.

### Example

Run this code

    #include <iostream>
    #include <experimental/filesystem>
    namespace fs = std::experimental::filesystem;
    int main()
    {
        fs::path p = fs::path("..") / ".." / "AppData";
        std::cout << "Current path is " << fs::current_path() << '\n'
                  << "Canonical path for " << p << " is " << fs::canonical(p) << '\n';
    }

Possible output:

    Current path is "C:\Users\abcdef\AppData\Local\Temp"
    Canonical path for "..\..\AppData" is "C:\Users\abcdef\AppData"

### See also

path | represents a path (class)
absolutesystem_complete | composes an absolute path converts a path to an absolute path replicating OS-specific behavior (function)

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