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

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

#include <iostream>
#include <filesystem>
 
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

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

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