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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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