Node:File Name Resolution, Next:File Name Errors, Previous:Directories, Up:File Names
A file name consists of file name components separated by slash
(/) characters. On the systems that the GNU C library supports,
multiple successive / characters are equivalent to a single
/ character.
The process of determining what file a file name refers to is called file name resolution. This is performed by examining the components that make up a file name in left-to-right order, and locating each successive component in the directory named by the previous component. Of course, each of the files that are referenced as directories must actually exist, be directories instead of regular files, and have the appropriate permissions to be accessible by the process; otherwise the file name resolution fails.
If a file name begins with a /, the first component in the file
name is located in the root directory of the process (usually all
processes on the system have the same root directory). Such a file name
is called an absolute file name.
Otherwise, the first component in the file name is located in the current working directory (see Working Directory). This kind of file name is called a relative file name.
The file name components . ("dot") and .. ("dot-dot")
have special meanings. Every directory has entries for these file name
components. The file name component . refers to the directory
itself, while the file name component .. refers to its
parent directory (the directory that contains the link for the
directory in question). As a special case, .. in the root
directory refers to the root directory itself, since it has no parent;
thus /.. is the same as /.
Here are some examples of file names:
/a
a, in the root directory.
/a/b
b, in the directory named a in the root directory.
a
a, in the current working directory.
/a/./b
/a/b.
./a
a, in the current working directory.
../a
a, in the parent directory of the current working
directory.
A file name that names a directory may optionally end in a /.
You can specify a file name of / to refer to the root directory,
but the empty string is not a meaningful file name. If you want to
refer to the current working directory, use a file name of . or
./.
Unlike some other operating systems, the GNU system doesn't have any
built-in support for file types (or extensions) or file versions as part
of its file name syntax. Many programs and utilities use conventions
for file names--for example, files containing C source code usually
have names suffixed with .c--but there is nothing in the file
system itself that enforces this kind of convention.