30 Input/output library [input.output]

A path that unambiguously identifies the location of a file without reference to an additional starting location.

The elements of a path that determine if it is absolute are operating system dependent.

A file within a file system that acts as a container of directory entries that contain information about other files, possibly including other directory files.

An object within a file system that holds user or system data.

Files can be written to, or read from, or both.

A file has certain attributes, including type.

File types include regular files and directories.

Other types of files, such as symbolic links ([fs.def.symlink]), may be supported by the implementation.

A collection of files and their attributes.

The condition that occurs when multiple threads, processes, or computers interleave access and modification of the same object within a file system.

The name of a file.

Filenames dot and dot-dot, 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

  :

  Some operating systems prohibit the ASCII control characters (0x00 – 0x1F) in filenames.

  — end example

   ]
• 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.

A link ([fs.def.link]) to an existing file.

Some file systems support multiple hard links to a file.

If the last hard link to a file is removed, the file itself is removed.

An object that associates a filename with a file.

Several links can associate names with the same file.

For narrow character strings, the operating system dependent current encoding for pathnames ([fs.def.pathname]).

For wide character strings, the implementation-defined execution wide-character set encoding ([lex.charset]).

The operating system dependent pathname format accepted by the host operating system.

A path in normal form is said to be normalized.

The process of obtaining a normalized path from a path that is not in normal form is called normalization.

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

   :

   The generic pathname grammar ([fs.path.generic]) defines directory-separator as one or more slashes and preferred-separators.

   — 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

   :

   These dot-dot filenames attempt to refer to nonexistent parent directories.

   — end note

    ]
7. If the last filename is dot-dot, remove any trailing directory-separator.
8. If the path is empty, add a dot.

Behavior that is dependent upon the behavior and characteristics of an operating system.

See [fs.conform.os].

⟨of a directory⟩ the directory that both contains a directory entry for the given directory and is represented by the filename dot-dot in the given directory.

⟨of other types of files⟩ a directory containing a directory entry for the file under discussion.

A sequence of elements that identify the location of a file within a filesystem.

The elements are the root-name, root-directory, and an optional sequence of filenames.

The maximum number of elements in the sequence is operating system dependent.

A character string that represents the name of a path.

Pathnames are formatted according to the generic pathname format grammar ([fs.path.generic]) or an operating system dependent native pathname format.

Pathname resolution is the operating system dependent mechanism for resolving a pathname to a particular file in a file hierarchy.

There may be multiple pathnames that resolve to the same file.

A path that is not absolute, and as such, only unambiguously identifies the location of a file when resolved ([fs.def.pathres]) relative to an implied starting location.

The elements of a path that determine if it is relative are operating system dependent.

A type of file with the property that when the file is encountered during pathname resolution, a string stored by the file is used to modify the pathname resolution.