Editing Inode (section)

===inode number conversion and file directory path retrieval===

It is typically not possible to map from an open file to the filename that was used to open it. When a program opens a file, the operating system converts the filename to an inode number and then discards the filename. As a result, functions like [[direct.h|{{mono|getcwd()}}]] and [[direct.h|{{mono|getwd()}}]] which retrieve the current [[working directory]] of the process, cannot directly access the filename.

Beginning with the current directory, these functions search up to its [[parent directory]], then to the parent's parent, and so on, until reaching the [[root directory]]. At each level, the function looks for a directory entry whose inode matches that of the directory it just moved up from. Because the child directory's inode still exists as an entry in its [[parent directory]], it allows the function to reconstruct the [[absolute path]] of the current [[working directory]].

Some operating systems maintain extra information to make this operation run faster. For example, in the [[Linux]] VFS,<ref>{{cite web | url = https://www.kernel.org/doc/html/latest/filesystems/vfs.html | title=Overview of the Linux Virtual File System | author=Gooch, Richard | editor=Enberg, Pekka | website=kernel.org | access-date=20 May 2023}}</ref> directory entry cache,<ref>{{cite web | url = https://www.kernel.org/doc/html/latest/filesystems/vfs.html#directory-entry-cache-dcache | title=Directory Entry Cache (dcache) | author=Richard Gooch | editor=Enberg, Pekka | website=kernel.org | access-date=20 May 2023}}</ref> also known as dentry or dcache, are cache entries used by the [[Kernel (operating system)|kernel]] to speed up filesystem operations by storing information about directory links in [[Random-access memory|RAM]].