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In computing, a symbolic link (also symlink or soft link) is a special type of file that contains a reference to another file or directory in the form of an absolute or relative path and that affects pathname resolution.〔(Pathname resolution ), POSIX.〕 Symbolic links were already present by 1978 in mini-computer operating systems from DEC and Data General's RDOS. Today they are supported by the POSIX operating-system standard, most Unix-like operating systems such as FreeBSD, GNU/Linux, and Mac OS X and Windows operating systems such as Windows 95, Windows Vista, Windows 7 and to some degree in Windows 2000 and Windows XP in the form of Shortcut files. ==Overview== A symbolic link contains a text string that is automatically interpreted and followed by the operating system as a path to another file or directory. This other file or directory is called the "target". The symbolic link is a second file that exists independently of its target. If a symbolic link is deleted, its target remains unaffected. If a symbolic link points to a target, and sometime later that target is moved, renamed or deleted, the symbolic link is not automatically updated or deleted, but continues to exist and still points to the old target, now a non-existing location or file. Symbolic links pointing to moved or non-existing targets are sometimes called ''broken'', ''orphaned'', ''dead'', or ''dangling''. Symbolic links are different from hard links. Hard links do not link paths on different volumes or file systems, whereas symbolic links may point to any file or directory irrespective of the volumes on which the link and target reside. Hard links always refer to an existing file, whereas symbolic links may contain an arbitrary path that does not point to anything. Symbolic links operate transparently for many operations: programs that read or write to files named by a symbolic link will behave as if operating directly on the target file. However, they have the effect of changing an otherwise hierarchical filesystem from a tree into a directed graph, which can have consequences for such simple operations as figuring out the current directory of a process. Even the Unix convention for navigating to a directory's parent directory no longer works reliably in the face of symlinks. Some shells heuristically try to uphold the illusion of a tree-shaped hierarchy, but when they do, this causes them to produce different results from other programs that manipulate pathnames without such heuristic, relying on the operating system instead. Programs that need to handle symbolic links specially (e.g., shells and backup utilities) thus need to identify and manipulate them directly. Some Unix as well as Linux distributions use symbolic links extensively in an effort to reorder the file system hierarchy. This is accomplished with several mechanisms, such as variant, context-dependent symbolic links. This offers the opportunity to create a more intuitive or application-specific directory tree and to reorganize the system without having to redesign the core set of system functions and utilities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Symbolic link」の詳細全文を読む スポンサード リンク
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