std::filesystem::relative, std::filesystem::proximate

 

C++

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Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

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Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

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::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate 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 relative( const std::filesystem::path& p,                std::error_code& ec );	(1)	(since C++17)
path relative( const std::filesystem::path& p,                const std::filesystem::path& base = std::filesystem::current_path() );	(2)	(since C++17)
path relative( const std::filesystem::path& p,                const std::filesystem::path& base,                std::error_code& ec );	(3)	(since C++17)
path proximate( const std::filesystem::path& p,                 std::error_code& ec );	(4)	(since C++17)
path proximate( const std::filesystem::path& p,                 const std::filesystem::path& base = std::filesystem::current_path() );	(5)	(since C++17)
path proximate( const std::filesystem::path& p,                 const std::filesystem::path& base,                 std::error_code& ec );	(6)	(since C++17)

1) Returns relative(p, current_path(), ec).

2,3) Returns p made relative to base. Resolves symlinks and normalizes both p and base before other processing. Effectively returns std::filesystem::weakly_canonical(p).lexically_relative(std::filesystem::weakly_canonical(base)) or std::filesystem::weakly_canonical(p, ec).lexically_relative(std::filesystem::weakly_canonical(base, ec)), except the error code form returns path() at the first error occurrence, if any.

4) Returns proximate(p, current_path(), ec).

5,6) Effectively returns std::filesystem::weakly_canonical(p).lexically_proximate(std::filesystem::weakly_canonical(base)) or std::filesystem::weakly_canonical(p, ec).lexically_proximate(std::filesystem::weakly_canonical(base, ec)), except the error code form returns path() at the first error occurrence, if any.

Parameters

p	-	an existing path
base	-	base path, against which p will be made relative/proximate
ec	-	error code to store error status to

Return value

1) p made relative against current_path().

2,3) p made relative against base.

4) p made proximate against current_path().

5,6) p made proximate against base.

Exceptions

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

2,5) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with p as the first path argument, base as the second path argument, and the OS error code as the error code argument.

1,3,4,6) Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur.

Example

Run this code

#include <filesystem>
#include <iostream>
 
void show(std::filesystem::path x, std::filesystem::path y)
{
    std::cout << "x:\t\t " << x << "\ny:\t\t " << y << '\n'
              << "relative(x, y):  "
              << std::filesystem::relative(x, y) << '\n'
              << "proximate(x, y): "
              << std::filesystem::proximate(x, y) << "\n\n";
}
 
int main()
{
    show("/a/b/c", "/a/b");
    show("/a/c", "/a/b");
    show("c", "/a/b");
    show("/a/b", "c");
}

Possible output:

x:               "/a/b/c"
y:               "/a/b"
relative(x, y):  "c"
proximate(x, y): "c"
 
x:               "/a/c"
y:               "/a/b"
relative(x, y):  "../c"
proximate(x, y): "../c"
 
x:               "c"
y:               "/a/b"
relative(x, y):  ""
proximate(x, y): "c"
 
x:               "/a/b"
y:               "c"
relative(x, y):  ""
proximate(x, y): "/a/b"

See also

path (C++17)	represents a path (class)
absolute (C++17)	composes an absolute path (function)
canonicalweakly_canonical (C++17)	composes a canonical path (function)
lexically_normallexically_relativelexically_proximate	converts path to normal form converts path to relative form converts path to proximate form (public member function of std::filesystem::path)