AppleSingle Format and AppleDouble Format are file formats developed by Apple Computer to store Mac OS"dual-forked" files on the Unix filesystem being used in A/UX, the Macintosh platform's first Unix-likeoperating system. AppleSingle combined both file forks and the related Finder meta-file information into a single file, whereas AppleDouble stored them as two separate files. Support for the formats was later added to Unix software such as NFS and MAE, but they saw little use outside this small market.
AppleSingle is similar in concept to the more popular MacBinary format, in that the resource and data forks are combined with a header containing the Finder information. In fact, the format is so similar, it seemed there was no reason why Apple did not simply use MacBinary instead, which by that point was widely known and used. Some not-so-obvious reasons are explained in an Internet Draft.[1] The format was later assigned the MIME typeapplication/applefile.
AppleDouble leaves the data fork in its original format, allowing it to be edited by normal Unix utilities. The resource fork and Finder information, both proprietary and lacking editors under Unix, were combined into a second file. A MIME type was also assigned to AppleDouble, multipart/appledouble. For sending to an AppleDouble un-aware system, the file was generally encoded using Base64, as opposed to being converted to AppleSingle.
Before Mac OS X, AppleSingle and Double had little presence in the Mac market, due largely to the small market share of A/UX. Nevertheless, they did force various file compression vendors to add support for the formats, and confuse future MacBinary versions.
Mac OS X revived the use of AppleDouble; on file systems such as NFS and WebDAV that do not natively support resource forks, Finder information, or extended attributes, that information is stored in AppleDouble format, with the second file having a name generated by prepending "._" to the name of the first file (thus, this information acts as a hidden file when viewed from a non-Apple Unix-based operating system). The files are sometimes moved to a separate directory called .AppleDouble. Metadata separation is also done in the OS X 10.3+ Finder Zip compression and the command line ditto utility, with a copy of the AppleDouble metadata stored in a __MACOSX directory.[2]
Manipulationedit
Unwanted "._" files can be removed using dot_clean -m on Mac OS X. Doing so also merges AppleDouble metadata with the corresponding files.[3] AppleDouble files can be manually created through creative abuse of ditto (which is AppleDouble-aware) and unzip (which is not).[4]
On other systems, the ad command[5] and a Perl script called apple_dump[6] can be used to view AppleDouble data. Both are part of Netatalk.
The macOS system provides a set of copyfile library functions that allows for packing and unpacking AppleSingle and AppleDouble files in C.[7]
Referencesedit
^C. Newman (July 1996). . IETF. Archived from the original on 2021-02-26.
RFC 1740 - MIME Encapsulation of Macintosh files – documents AppleSingle/Double in appendixes
Mac Binary Converter, an open source tool for converting between different Macintosh file encodings.
Mac::AppleSingleDouble, a Perl module for reading AppleSingle and AppleDouble files
, Apple Inc. knowledgebase note about the AppleDouble format
December 15, 2023
applesingle, appledouble, formats, this, article, possibly, contains, original, research, please, improve, verifying, claims, made, adding, inline, citations, statements, consisting, only, original, research, should, removed, april, 2010, learn, when, remove, . This article possibly contains original research Please improve it by verifying the claims made and adding inline citations Statements consisting only of original research should be removed April 2010 Learn how and when to remove this template message AppleSingle Format and AppleDouble Format are file formats developed by Apple Computer to store Mac OS dual forked files on the Unix filesystem being used in A UX the Macintosh platform s first Unix like operating system AppleSingle combined both file forks and the related Finder meta file information into a single file whereas AppleDouble stored them as two separate files Support for the formats was later added to Unix software such as NFS and MAE but they saw little use outside this small market AppleSingle is similar in concept to the more popular MacBinary format in that the resource and data forks are combined with a header containing the Finder information In fact the format is so similar it seemed there was no reason why Apple did not simply use MacBinary instead which by that point was widely known and used Some not so obvious reasons are explained in an Internet Draft 1 The format was later assigned the MIME type application applefile AppleDouble leaves the data fork in its original format allowing it to be edited by normal Unix utilities The resource fork and Finder information both proprietary and lacking editors under Unix were combined into a second file A MIME type was also assigned to AppleDouble multipart appledouble For sending to an AppleDouble un aware system the file was generally encoded using Base64 as opposed to being converted to AppleSingle Contents 1 Usage 2 Manipulation 3 References 4 External linksUsage editBefore Mac OS X AppleSingle and Double had little presence in the Mac market due largely to the small market share of A UX Nevertheless they did force various file compression vendors to add support for the formats and confuse future MacBinary versions Mac OS X revived the use of AppleDouble on file systems such as NFS and WebDAV that do not natively support resource forks Finder information or extended attributes that information is stored in AppleDouble format with the second file having a name generated by prepending to the name of the first file thus this information acts as a hidden file when viewed from a non Apple Unix based operating system The files are sometimes moved to a separate directory called AppleDouble Metadata separation is also done in the OS X 10 3 Finder Zip compression and the command line ditto utility with a copy of the AppleDouble metadata stored in a MACOSX directory 2 Manipulation editUnwanted files can be removed using dot clean m on Mac OS X Doing so also merges AppleDouble metadata with the corresponding files 3 AppleDouble files can be manually created through creative abuse of ditto which is AppleDouble aware and unzip which is not 4 On other systems the ad command 5 and a Perl script called apple dump 6 can be used to view AppleDouble data Both are part of Netatalk The macOS system provides a set of copyfile library functions that allows for packing and unpacking AppleSingle and AppleDouble files in C 7 References edit C Newman July 1996 MacBinary and Binhex 4 0 considered harmful IETF Archived from the original on 2021 02 26 ditto 1 Darwin and macOS General Commands Manual dot clean 1 Darwin and macOS General Commands Manual terminal How to convert a file with extended attributes to AppleDouble format Stack Exchange Retrieved 2021 09 12 ad 1 Linux General Commands Manual apple dump 1 Linux General Commands Manual copyfile 3 Darwin and macOS Library Functions ManualExternal links editAppleSingle and AppleDouble format internals from the original A UX documentation RFC 1740 MIME Encapsulation of Macintosh files documents AppleSingle Double in appendixes Mac Binary Converter an open source tool for converting between different Macintosh file encodings Mac AppleSingleDouble a Perl module for reading AppleSingle and AppleDouble files Mac OS X Apple Double Format Creates File Name With the Prefix Apple Inc knowledgebase note about the AppleDouble format Retrieved from https en wikipedia org w index php title AppleSingle and AppleDouble formats amp oldid 1148901015, wikipedia, wiki, book, books, library,
