std::filesystem::canonical

 

C++

Language

Standard library headers

Concepts

Utilities 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>
path canonical( const std::filesystem::path& p,                 const std::filesystem::path& base = std::filesystem::current_path() );	(1)	(since C++17)
path canonical( const std::filesystem::path& p,                 std::error_code& ec );	(2)	(since C++17)
path canonical( const std::filesystem::path& p,                 const std::filesystem::path& base,                 std::error_code& ec );	(3)	(since C++17)

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 std::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 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

  

This function is modeled after the POSIX realpath.

Example

Run this code

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    fs::path p = fs::path("..") / ".." / "AppData";
    std::cout << "Current path is " << fs::current_path() << '\n'
              << "Canonical path for " << p << " is " << 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 (C++17)	represents a path (class)
absolutesystem_complete (C++17)(C++17)	composes an absolute path converts a path to an absolute path replicating OS-specific behavior (function)