Organization of the file system
Inside one sheet file directory names are unique. The names of the files in
different directories can match. In order to clearly define the file on his
behalf (to avoid conflicts of names) decided to call a full file name (pathname),
which consists of a list of names of sub-directories, which can be found on the
path from root to the file, plus the file name in the directory containing the
data directly file. Thus, the name includes the names-chain path to the file,
such as / usr / ast / mailbox. This so-called absolute name. Such names are
unique. Components shared ways characters' / '(slash) in the Unix or backward in
escaping MS-DOS (in Multics -'>'). Another way in which a name is a relative
path to the file. He uses the concept or the current working directory, which is
part of the environment (environment) process, working with the file. For
example, the Linux OS working directory is part of the structure of the process.
Then the files in a directory can be invoked only by name, the file search will
be carried out in the working directory. This is a convenient but essentially
the same thing as absolute form. To gain access to the file and its containment
system must comply blocks to navigate directories. Consider for example the path
/ usr / linux / progr.c. Algorithm same for all hierarchical systems. First, in
a fixed location on the disk is the root directory. Then component is the path
usr, that is at the root directory searched file / usr. Exploring the file
system understands that this file is a directory, and blocks of data the file
regards as a list of files and looking for the next component of linux. Of the
line for linux is file related component usr / linux. Then progr.c also is a
component, which then was called, entered in the table and open files stored in
it before the closure of the file. Deviation from the model pathname handling
components can be the case when this is not a normal component catalog with the
initial node him and the list of files, and provides a mount point to another
file archive of the file system. This case dealt with in the next chapter. Many
applications work with the files located in the current directory, did not
explicitly specifying its name. This enables the user to arbitrarily call
directories containing different software packages. To realize this opportunity,
in most OS supporting hierarchical directory structure used symbol '.' For the
current directory and '..' to the parent. Set the path to the file in some OS
file systems differ so, how to begin this conversation names. In this regard,
there are several options. In some systems, the file management requires that
each archive files (full tree of directories) located entirely on the same disk
(or logical drive, section of physical disk package submitted by the means of
operating system as a separate drive). In this case, the full name of the file
name begins with a disk device, where the corresponding drive (drive letters).
For example, c: \ util \ nu-ndd.exe. This method is used in naming firms DEC
file systems and Microsoft
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