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Function std.path.asRelativePath

Transforms path into a path relative to base.

auto auto asRelativePath(CaseSensitive cs = CaseSensitive.osDefault, R1, R2) (
  R1 path,
  R2 base
if ((isNarrowString!R1 || isRandomAccessRange!R1 && hasSlicing!R1 && isSomeChar!(ElementType!R1) && !isConvertibleToString!R1) && (isNarrowString!R2 || isRandomAccessRange!R2 && hasSlicing!R2 && isSomeChar!(ElementType!R2) && !isConvertibleToString!R2));

The returned path is relative to base, which is usually the current working directory. base must be an absolute path, and it is always assumed to refer to a directory. If path and base refer to the same directory, the function returns '.'.

The following algorithm is used:

  1. If path is a relative directory, return it unaltered.
  2. Find a common root between path and base. If there is no common root, return path unaltered.
  3. Prepare a string with as many ../ or ..\ as necessary to reach the common root from base path.
  4. Append the remaining segments of path to the string and return.

In the second step, path components are compared using filenameCmp!cs, where cs is an optional template parameter determining whether the comparison is case sensitive or not. See the filenameCmp documentation for details.


path path to transform
base absolute path
cs whether filespec comparisons are sensitive or not; defaults to CaseSensitive.osDefault


a random access range of the transformed path

See Also



import std.array;
version (Posix)
    writeln(asRelativePath("foo", "/bar").array); // "foo"
    writeln(asRelativePath("/foo/bar", "/foo/bar").array); // "."
    writeln(asRelativePath("/foo/bar", "/foo/baz").array); // "../bar"
    writeln(asRelativePath("/foo/bar/baz", "/foo/woo/wee").array); // "../../bar/baz"
    writeln(asRelativePath("/foo/bar/baz", "/foo/bar").array); // "baz"
else version (Windows)
    writeln(asRelativePath("foo", `c:\bar`).array); // "foo"
    writeln(asRelativePath(`c:\foo\bar`, `c:\foo\bar`).array); // "."
    writeln(asRelativePath(`c:\foo\bar`, `c:\foo\baz`).array); // `..\bar`
    writeln(asRelativePath(`c:\foo\bar\baz`, `c:\foo\woo\wee`).array); // `..\..\bar\baz`
    writeln(asRelativePath(`c:/foo/bar/baz`, `c:\foo\woo\wee`).array); // `..\..\bar\baz`
    writeln(asRelativePath(`c:\foo\bar\baz`, `c:\foo\bar`).array); // "baz"
    writeln(asRelativePath(`c:\foo\bar`, `d:\foo`).array); // `c:\foo\bar`
    writeln(asRelativePath(`\\foo\bar`, `c:\foo`).array); // `\\foo\bar`
    static assert(0);


Lars Tandle Kyllingstad, Walter Bright, Grzegorz Adam Hankiewicz, Thomas Kühne, Andrei Alexandrescu


Boost License 1.0