Editing Filename mangling

{{Short description|Translation of the file name for compatibility at the operating system level}}
{{about|the mangling of filenames for operating system compatibility|the concept of name mangling within compilers|name mangling}}
{{Refimprove|date=July 2007}}

The process of '''filename mangling''', in [[computing]], involves a translation of the file name for compatibility at the [[operating system]] level. It occurs when a [[filename]] on a [[filesystem]] appears in a form incompatible with the operating system accessing it. Such mangling occurs, for example, on [[computer network]]s when a [[Microsoft Windows|Windows]] machine attempts to access a file on a [[Unix]] server and that  file has a filename which includes characters not valid in Windows.

==FAT Derivative Filesystem==
{{main|File Allocation Table|8.3}}

===Legacy support under VFAT===

A common example of name mangling occurs on [[File Allocation Table|VFAT]] file systems on versions of Windows from [[Windows 95]] onwards. The VFAT specification{{clarify|date=December 2016}} allows [[Long File Name]]s (LFNs). For backwards-compatibility with [[MS-DOS]] and older Windows software, which recognizes filenames of a maximum of 11 characters in length with [[8.3]] format (i.e.: an eight-letter filename, a dot and a three-letter extension, such as <code>autoexec.bat</code>), files with LFNs get stored on disk in 8.3 format (<code>longfilename.txt</code> becoming <code>longfi~1.txt</code>), with the long file name stored elsewhere on the disk.

Normally{{clarify|date=December 2016}}, when using compatible Windows programs which use standard Windows methods{{which|date=December 2016}} of reading the disk, the [[input/output|I/O]] subsystem returns the long filename to the program &mdash; however, if an old DOS application or an old Windows application tries to address the file, it will use the older, 8.3-only APIs, or work at a lower level and perform its own disk access, which results in the return of an 8.3 filename. In this case, the filenames become mangled by taking the first six non-space characters in the filename and adding a [[tilde]] (~) and then a number to ensure the uniqueness of the 8.3 filename on the disk. This mangling scheme can turn (for example) <code>Program Files</code> into <code>PROGRA~1</code>.  This technique persists today when people use [[DOSBox]] to play classic DOS games or use [[Windows 3.1]] in conjunction to play [[Win16]] games on 64-bit Windows.

==Unix Filesystems==
{{which|date=December 2016}}

Unix file names can contain [[colon (punctuation)|colon]]s or [[backslash]]es, whereas Windows interprets such characters in other{{which|date=December 2016}} ways. Accordingly{{clarify|date=December 2016}}, software could mangle the Unix file "Notes: 11\04\03" as "Notes_ 11-04-03" to enable Windows software to remotely access the file. Other [[Unix-like]] systems, such as [[Samba software|Samba]] on Unix, use different{{clarify|date=December 2016}} mangling systems to map long filenames to DOS-compatible filenames (although Samba administrators can configure this behavior in the config file).<ref>{{cite book
|last= Eckstein
|first= Robert
|author2=David Collier-Brown |author3=Peter Kelly
|title= Using Samba
|url= http://oreilly.com/catalog/samba/chapter/book/ch05_04.html
|accessdate= 2009-10-23
|edition= 1st
|date= November 1999
|publisher= O'Reilly & Associates, Inc
|chapter= 5.4 Name Mangling and Case
}}
</ref>

==Mac OS==

[[macOS]]'s [[Finder (software)|Finder]] displays instances of "[[Colon (punctuation)|:]]" in file and directory names with a "[[Slash (punctuation)|/]]". This is because the [[classic Mac OS]] used the ":" character internally as a path separator. Listing these files or directories using a [[terminal emulator]] displays a ":" rather than the "/" character, though.

==References==
{{Reflist}}


{{Computer files}}
[[Category:Computer file systems]]
[[Category:Computer files]]