cpp/filesystem/path

Objects of type represent paths on a filesystem. Only syntactic aspects of paths are handled: the pathname may represent a non-existing path or even one that is not allowed to exist on the current file system or OS.

The path name has the following syntax:
 * : identifies the root on a filesystem with multiple roots (such as or ). In case of ambiguity, the longest sequence of characters that forms a valid  is treated as the . The standard library may define additional root-names besides the ones understood by the OS API.
 * : a directory separator that, if present, marks this path as absolute. If it is missing (and the first element other than the root name is a file name), then the path is relative and requires another path as the starting location to resolve to a file name.
 * 1) Zero or more of the following:
 * : sequence of characters that aren't directory separators or preferred directory separators (additional limitations may be imposed by the OS or file system). This name may identify a file, a hard link, a symbolic link, or a directory. Two special s are recognized:
 * : the file name consisting of a single dot character is a directory name that refers to the current directory
 * : the file name consisting of two dot characters is a directory name that refers to the parent directory.
 * s: the forward slash character or the alternative character provided as . If this character is repeated, it is treated as a single directory separator:  is the same as

A path can be normalized by following this algorithm:
 * 1) If the path is empty, stop (normal form of an empty path is an empty path)
 * 2) Replace each  (which may consist of multiple slashes) with a single.
 * 3) Replace each slash character in the  with.
 * 4) Remove each  and any immediately following.
 * 5) Remove each non- filename immediately followed by a  and a, along with any immediately following.
 * 6) If there is, remove all s and any s immediately following them.
 * 7) If the last filename is, remove any trailing.
 * 8) If the path is empty, add a  (normal form of  is )

The path can be traversed element-wise via iterators returned by the begin and end functions, which views the path in generic format and iterates over root name, root directory, and the subsequent file name elements (directory separators are skipped except the one that identifies the root directory). If the very last element in the path is a directory separator, the last iterator will dereference to an empty element.

Calling any non-const member function of a invalidates all iterators referring to elements of that object.

If the OS uses a native syntax that is different from the portable generic syntax described above, library functions that are defined to accept "detected format" accept path names in both formats: a detected format argument is taken to be in the generic format if and only if it matches the generic format but is not acceptable to the operating system as a native path. On those OS where native format differs between pathnames of directories and pathnames of files, a generic pathname is treated as a directory path if it ends on a directory separator and a regular file otherwise.

In any case, the path class behaves as if it stores a pathname in the native format and automatically converts to generic format as needed (each member function specifies which format it interprets the path as)

On POSIX systems, the generic format is the native format and there is no need to distinguish or convert between them.

Paths are implicitly convertible to and from stds, which makes it possible to use them with other file APIs.

The use std so that spaces do not cause truncation when later read by.

Decomposition member functions (e.g. extension) return objects instead of string objects as other APIs do.