10 KiB
[fs.path.generic]
31 Input/output library [input.output]
31.12 File systems [filesystems]
31.12.6 Class path [fs.class.path]
31.12.6.2 Generic pathname format [fs.path.generic]
pathname:
root-nameopt root-directoryopt relative-path
root-name:
operating system dependent sequences of characters
implementation-defined sequences of characters
root-directory:
directory-separator
relative-path:
filename
filename directory-separator relative-path
an empty path
filename:
non-empty sequence of characters other than directory-separator characters
directory-separator:
preferred-separator directory-separatoropt
fallback-separator directory-separatoropt
preferred-separator:
operating system dependent directory separator character
fallback-separator:
/, if preferred-separator is not /
A filename is the name of a file.
The dot and dot-dot filenames, consisting solely of one and two period characters respectively, have special meaning.
The following characteristics of filenames are operating system dependent:
-
The permitted characters. [Example 1: Some operating systems prohibit the ASCII control characters (0x00 â 0x1F) in filenames. â end example] [Note 1: Wider portability can be achieved by limiting filename characters to the POSIX Portable Filename Character Set:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 . _ - â end note] -
The maximum permitted length.
-
Filenames that are not permitted.
-
Filenames that have special meaning.
-
Case awareness and sensitivity during path resolution.
-
Special rules that may apply to file types other than regular files, such as directories.
Except in a root-name, multiple successive directory-separator characters are considered to be the same as one directory-separator character.
The dot filename is treated as a reference to the current directory.
The dot-dot filename is treated as a reference to the parent directory.
What the dot-dot filename refers to relative to root-directory is implementation-defined.
Specific filenames may have special meanings for a particular operating system.
A root-name identifies the starting location for pathname resolution ([fs.class.path]).
If there are no operating system dependent root-names, at least one implementation-defined root-name is required.
[Note 2:
Many operating systems define a name beginning with two directory-separator characters as a root-name that identifies network or other resource locations.
Some operating systems define a single letter followed by a colon as a drive specifier â a root-name identifying a specific device such as a disk drive.
â end note]
If a root-name is otherwise ambiguous, the possibility with the longest sequence of characters is chosen.
[Note 3:
On a POSIX-like operating system, it is impossible to have aroot-name and a relative-path without an intervening root-directory element.
â end note]
Normalization of a generic format pathname means:
| 1. | If the path is empty, stop. |
|---|---|
| 2. | Replace each slash character in the root-name with a preferred-separator. |
| 3. | Replace each directory-separator with a preferred-separator. [Note 4: The generic pathname grammar defines directory-separator as one or more slashes and preferred-separators. â end note] |
| 4. | Remove each dot filename and any immediately following directory-separator. |
| 5. | As long as any appear, remove a non-dot-dot filename immediately followed by a directory-separator and a dot-dot filename, along with any immediately following directory-separator. |
| 6. | If there is a root-directory, remove all dot-dot filenames and any directory-separators immediately following them. [Note 5: These dot-dot filenames attempt to refer to nonexistent parent directories. â end note] |
| 7. | If the last filename is dot-dot, remove any trailing directory-separator. |
| 8. | If the path is empty, add a dot. |
The result of normalization is a path in normal form, which is said to be normalized.