15.1.3 Unix and Mac OS Paths

In a path on Unix and Mac OS, a / separates elements of the path, . as a path element always means the directory indicated by preceding path, and .. as a path element always means the parent of the directory indicated by the preceding path. A leading ~ in a path is not treated specially, but expand-user-path can be used to convert a leading ~ element to a user-specific directory. No other character or byte has a special meaning within a path. Multiple adjacent / are equivalent to a single / (i.e., they act as a single path separator).

A path root is always /. A path starting with / is an absolute, complete path, and a path starting with any other character is a relative path.

Any pathname that ends with a / syntactically refers to a directory, as does any path whose last element is . or ...

A Unix and Mac OS path is cleansed by replacing multiple adjacent /s with a single /.

For (bytes->path-element bstr), bstr must not contain any /, otherwise the exn:fail:contract exception is raised. The result of (path-element->bytes path) or (path-element->string path) is always the same as the result of (path->bytes path) and (path->string path). Since that is not the case for other platforms, however, path-element->bytes and path-element->string should be used when converting individual path elements.

On Mac OS, Finder aliases are zero-length files.

15.1.3.1 Unix Path Representation

A path on Unix and Mac OS is natively a byte string. For presentation to users and for other string-based operations, a path is converted to/from a string using the current locale’s encoding with ? (encoding) or #\uFFFD (decoding) in place of errors. Beware that the encoding may not accommodate all possible paths as distinct strings.