|
|
|
|
|
# Paths
|
|
|
|
|
|
|
|
|
|
|
|
A _path_ encapsulates a filesystem path that \(potentially\) names a
|
|
|
|
|
|
file or directory. Although paths can be converted to and from strings
|
|
|
|
|
|
and byte strings, neither strings nor byte strings are suitable for
|
|
|
|
|
|
representing general paths. The problem is that paths are represented in
|
|
|
|
|
|
the filesystem as either byte sequences or UTF-16 sequences \(depending
|
|
|
|
|
|
on the operating systems\); the sequences are not always human-readable,
|
|
|
|
|
|
and not all sequences can be decoded to Unicode scalar values.
|
|
|
|
|
|
|
|
|
|
|
|
Despite the occasional encoding problems, most paths can be converted to
|
|
|
|
|
|
and from strings. Thus, procedures that accept a path argument always
|
|
|
|
|
|
accept a string, and the printed form of a path uses the string decoding
|
|
|
|
|
|
of the path inside `#<path:` and `>`. The `display` form of a path is
|
|
|
|
|
|
the same as the `display` form of its string encodings.
|
|
|
|
|
|
|
|
|
|
|
|
Examples:
|
|
|
|
|
|
|
|
|
|
|
|
```racket
|
|
|
|
|
|
> (string->path "my-data.txt")
|
|
|
|
|
|
#<path:my-data.txt>
|
|
|
|
|
|
> (file-exists? "my-data.txt")
|
|
|
|
|
|
#f
|
|
|
|
|
|
> (file-exists? (string->path "my-data.txt"))
|
|
|
|
|
|
#f
|
|
|
|
|
|
> (display (string->path "my-data.txt"))
|
|
|
|
|
|
my-data.txt
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
Procedures that produce references to the filesystem always produce path
|
|
|
|
|
|
values, instead of strings.
|
|
|
|
|
|
|
|
|
|
|
|
Example:
|
|
|
|
|
|
|
|
|
|
|
|
```racket
|
|
|
|
|
|
> (path-replace-suffix "foo.scm" #".rkt")
|
|
|
|
|
|
#<path:foo.rkt>
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
Although it’s sometimes tempting to directly manipulate strings that
|
|
|
|
|
|
represent filesystem paths, correctly manipulating a path can be
|
|
|
|
|
|
surprisingly difficult. Windows path manipulation is especially tricky,
|
|
|
|
|
|
because path elements like `"aux"` can have special meanings.
|
|
|
|
|
|
|
|
|
|
|
|
> +\[missing\] in \[missing\] documents the fine points of Windows
|
|
|
|
|
|
> filesystem paths.
|
|
|
|
|
|
|
|
|
|
|
|
Use procedures like `split-path` and `build-path` to deconstruct and
|
|
|
|
|
|
construct paths. When you must manipulate the name of a specific path
|
|
|
|
|
|
element \(i.e., a file or directory component in a path\), use
|
|
|
|
|
|
procedures like `path-element->bytes` and `bytes->path-element`.
|
|
|
|
|
|
|
|
|
|
|
|
Examples:
|
|
|
|
|
|
|
|
|
|
|
|
```racket
|
|
|
|
|
|
> (build-path "easy" "file.rkt")
|
|
|
|
|
|
#<path:easy/file.rkt>
|
|
|
|
|
|
> (split-path (build-path "easy" "file.rkt"))
|
|
|
|
|
|
#<path:easy/>
|
|
|
|
|
|
#<path:file.rkt>
|
|
|
|
|
|
#f
|
|
|
|
|
|
```
|
