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

 

C++

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Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

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Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

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()); path relative( const std::filesystem::path& p,                const std::filesystem::path& base,                std::error_code& ec );	(2)	(since C++17)
path proximate( const std::filesystem::path& p,                 std::error_code& ec );	(3)	(since C++17)
path proximate( const std::filesystem::path& p,                 const std::filesystem::path& base = std::filesystem::current_path()); path proximate( const std::filesystem::path& p,                 const std::filesystem::path& base,                 std::error_code& ec );	(4)	(since C++17)

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

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

3) Returns proximate(p, current_path(), ec)

4) Effectively returns weakly_canonical(p).lexically_proximate(weakly_canonical(base)) or weakly_canonical(p, ec).lexically_proximate(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 base.

2) p made proximate against base

Exceptions

The overload that does not take a std::error_code& parameter throws 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. 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.

Example

Run this code

#include <iostream>
#include <filesystem>
 
void show(std::filesystem::path a, std::filesystem::path b)
{
    std::cout << "relative (" << a << "," << b << ") == ";
    std::cout << std::filesystem::relative(a,b) << "\n";
 
    std::cout << "proximate(" << a << "," << b << ") == ";
    std::cout << std::filesystem::proximate(a,b) << "\n";
}
 
int main()
{
    show("/a/b/c","/a/b");
    show("/a/c","/a/b");
    show("c","/a/b");
    show("/a/b","c");
}

Possible output:

relative ("/a/b/c","/a/b") == "c"
proximate("/a/b/c","/a/b") == "c"
relative ("/a/c","/a/b") == "../c"
proximate("/a/c","/a/b") == "../c"
relative ("c","/a/b") == ""
proximate("c","/a/b") == "c"
relative ("/a/b","c") == ""
proximate("/a/b","c") == "/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)