Mac OS Alias
| Type code | alis |
|---|---|
| Uniform Type Identifier (UTI) | com.apple.alias-file |
| Magic number | 'book0000mark0000' |
| Developed by | Apple, Inc. |
| Type of format | shortcut |
In classic Mac OSSystem 7 and later, and in macOS, an alias is a small file that represents another object in a local, remote, or removable[1]file system and provides a dynamic link to it; the target object may be moved or renamed, and the alias will still link to it (unless the original file is recreated; such an alias is ambiguous and how it is resolved depends on the version of macOS). In Windows, a 'shortcut', a file with a .lnk extension, performs a similar function.
It is similar to the Unixsymbolic link, but with the distinction of working even if the target file moves to another location on the same disk (in this case it acts like a hard link, but the source and target of the link may be on different filesystems, and the target of the link may be a directory). As a descendant of BSD, macOS supports Unix symbolic (and hard) links as well.
Mac OS, operating system (OS) developed by the American computer company Apple Inc. The OS was introduced in 1984 to run the company's Macintosh line of personal computers (PCs). The Macintosh heralded the era of graphical user interface (GUI) systems, and it inspired Microsoft Corporation to develop its own GUI, the Windows OS. Like -r, but only ANSI 'color' escape sequences are output in 'raw' form. Unlike -r, the screen appearance is maintained correctly in most cases. ANSI 'color' escape sequences are sequences of the form: ESC. Macintosh Operating System: The Macintosh Operating System (Mac OS) is an operating system (OS) designed by Apple Inc. To be installed and operated on the Apple Macintosh series of computers. Introduced in 1984, it is a graphical user interface (GUI) based OS that has since been released as multiple different versions. Initially, Mac OS was.
Function[edit]
An alias acts as a stand-in for any object in the file system, such as a document, an application, a folder, a hard disk, a network share or removable medium or a printer. When double-clicked, the computer will act the same way as if the original file had been double-clicked. Likewise, choosing an alias file from within a 'File Open' dialog box would open the original file. The purpose of an alias is to assist the user in managing large numbers of files by providing alternative ways to access them without having to copy the files themselves. While a typical alias under the classic Mac OS was small, between 1 and 5 KB, under macOS it can be fairly large, more than 5 MB (5000 KB) for the alias to a folder.
Preventing alias failure[edit]
An alias is a dynamic reference to an object. The original may be moved to another place within the same filesystem, without breaking the link. The operating system stores several pieces of information about the original in the resource fork of the alias file. Examples of the information used to locate the original are:
- path
- file ID (inode number)
- directory ID (inode number)
- name
- file size
Since any of these properties can change without the computer's knowledge, as a result of user activity, various search algorithms are used to find the most plausible target. This fault-tolerance sets the alias apart from similar functions in some other operating systems, such as the Unixsymbolic link or the Microsoft Windowsshortcut, at the expense of increased complexity and unpredictability. For example, an application can be moved from one directory to another within the same filesystem, but an existing alias would still launch the same application when double-clicked.
The question can arise of how an alias should work if a file is moved, and then a file is created with the same name as the original moved file, since the alias can be used to locate both the original name and the new location of the original file. With symbolic links the reference is unambiguous (soft links refer to the new file, hard links to the original). Before Mac OS X 10.2, however, such an ambiguous alias would consistently find the original moved file, rather than the recreated file. In Mac OS X 10.2 and later releases, the new file is found, matching the behaviour of symbolic links [1]. macOS applications can programmatically use the old behavior if required.
Richys nightmares mac os. Aliases are similar in operation to shadows in the graphical Workplace Shell of the OS/2 operating system.
Distinguishing marks[edit]
In System 7 through Mac OS 9, aliases distinguished themselves visually to the user by the fact that their file names were in italics. To accommodate languages that don't have italics (such as Japanese), in Mac OS 8.5 another distinguishing mark was added, badging with an 'alias arrow'—a black arrow with a small white border—similar to that used for shortcuts in Microsoft Windows.
In macOS, the filenames of aliases are not italicized, but the arrow badge remains.
File structure[edit]
The alias files in macOS start by the magic number62 6F 6F 6B 00 00 00 00 6D 61 72 6B 00 00 00 00 which is in ASCIIbook␀␀␀␀mark␀␀␀␀ (␀ representing the Null character).
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Following the magic number, it has been reported that an alias has a set of records inside it, each record is 150 bytes long and consists of the fields shown below (all integers are big endian).[2] However, alias files are far larger than this would explain, and include other information at least including icons.[3][4]
- 4 bytes user type name/app creator code = long ASCII text string (none = 0)
- 2 bytes record size = short unsigned total length
- 2 bytes record version = short integer version (current version = 2)
- 2 bytes alias kind = short integer value (file = 0; directory = 1)
- 1 byte volume name string length = byte unsigned length
- 27 bytes volume name string (if volume name string < 27 chars then pad with zeros)
- 4 bytes volume created mac date = long unsigned value in seconds since beginning 1904 to 2040
- 2 bytes volume signature = short unsigned HFS value
- 2 bytes volume type = short integer mac os value (types are Fixed HD = 0; Network Disk = 1; 400kB FD = 2;800kB FD = 3; 1.4MB FD = 4; Other Ejectable Media = 5 )
- 4 bytes parent directory id = long unsigned HFS value
- 1 bytes file name string length = byte unsigned length
- 63 bytes file name string (if file name string < 63 chars then pad with zeros)
- 4 bytes file number = long unsigned HFS value
- 4 bytes file created mac date = long unsigned value in seconds since beginning 1904 to 2040
- 4 bytes file type name = long ASCII text string
- 4 bytes file creator name = long ASCII text string
- 2 bytes nlvl From (directories from alias thru to root) = short integer range
- 2 bytes nlvl To (directories from root thru to source) = short integer range (if alias on different volume then set above to -1)
- 4 bytes volume attributes = long hex flags
- 2 bytes volume file system id = short integer HFS value
- 10 bytes reserved = 80-bit value set to zero
- 4+ bytes optional extra data strings = short integer type + short unsigned string length (types are Extended Info End = -1; Directory Name = 0; Directory IDs = 1; Absolute Path = 2; AppleShare Zone Name = 3; AppleShare Server Name = 4; AppleShare User Name = 5; Driver Name = 6; Revised AppleShare info = 9; AppleRemoteAccess dialup info = 10)
- string data = hex dump
- odd lengths have a 1 byte odd string length pad = byte value set to zero
Alias record structure outside of size length[edit]
The following is for use with the Apple's Alias Resource Manager.
- 4 bytes resource type name = long ASCII text string
- 2 bytes resource ID = short integer value
- 2 bytes resource end pad = short value set to zero
Java code to flag an alias file
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https://flashplaynagamescasinochick-free-bet.peatix.com. There is a github repo with working C++ code here.
Managing aliases[edit]
User interface[edit]
In System 7, the only way to create an alias was to select the original and choose 'Make Alias' from the 'File' menu. An alias, with the same name and ' alias' appended would then be created in the same folder. In later versions, it became possible to create aliases by drag-and-drop, while holding down the command and option modifier keys.
Mac OS 8.5 added a feature for re-connecting aliases that had been broken for one reason or another (when the simple search algorithms failed to find a reliable replacement). This was done by selecting a new target through the standard Open File dialog.
In Mac OS 8.5 options were added for command-optiondragging an object in the Finder to create an alias at that location. This is where the alias cursor was added to the system. The cursor mirrors the appearance of the 'create shortcut' cursor on Windows systems.
Programming API[edit]
The Alias Manager API is part of Carbon. It is unknown whether it was present in Mac OS Classic.[5] Desert nights casino no deposit.
Mac OS X 10.6 introduced some alias-related APIs to Cocoa, as a part of NSURL.[6]
Relation to BSD symbolic and hard links[edit]
Unix and similar operating systems provide 2 features very similar to macOS aliases: symbolic links and hard links. When using the macOS Finder, links are displayed and treated largely like macOS aliases, and even carry an identical 'Kind' attribute. However, when using the shell command line, macOS aliases are not recognized: for example, you cannot use the cd command with the name of an alias file. This is because an alias is implemented as a file on the disk that must be interpreted by an API while links are implemented within the filesystem and are thus functional at any level of the OS.
There is currently no pre-installed command to resolve an alias to the path of the file or directory it refers to. However, a freely available C program makes use of the Mac Carbon APIs to perform this task.[7] Given that, commands such as cd Sleep walkers maze mac os. can be set up to check for aliases and treat them just like symbolic or hard links.
References[edit]
- ^Files: Chapter 4 - Alias Manager; Search Strategies — Inside Macintosh developer documentation
- ^Some information about MacOS aliases collected from the web. (reverse engineering effort)
- ^Forum discussion of the large size of aliases.
- ^'Further details, including changes with various Mac OS versions'. Archived from the original on 2013-04-30. Retrieved 2018-10-11.
- ^'Alias Manager'. Apple Developer Documentation.
- ^https://github.com/nathanday/ndalias/issues/3
- ^Davis, Thos. 'getTrueName.c'. Mac OS X Hints. IDG. Retrieved 24 October 2016.
External links[edit]
- System 7 aliases — Article about System 7 aliases, from 1992
You can choose from icon, list, column, or Cover Flow view. In Cover Flow view, the browser is split horizontally into two sections. The top section is a graphical view of each item, such as folder icons or a preview of the first page of a document. The bottom section is a list view of the items.
To jump, press VO-J. If you're using VoiceOver gestures, keep a finger on the trackpad and press the Control key.
Icon view: Use the arrow keys to move to the item you want.
List view: To move down the list rows, press VO-Down Arrow. To expand and collapse a folder, press VO-. To move the VoiceOver cursor across a row and hear information about an item, press VO-Right Arrow. Or press VO-R to hear the entire row read at once.
Column view: To move down the list until you find the folder or file you want, use the Down Arrow key. To move into subfolders, press the Right Arrow key.
Cover Flow view: To flip through the items in the top section and move automatically through the corresponding list rows in the bottom section, press the Left Arrow or Right Arrow key.
When you find the file or folder you want to open, use the Finder shortcut Command-O or Command-Down Arrow to open it.VoiceOver announces when you have selected an alias or a file or folder you don't have permission to open. Moonbase mac os.
