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To make the alias permanent, you will need to edit a file called “.bashprofile” by running the following command: nano /.bashprofile This will open nano (a command line text editor). Jan 18, 2018 In Mac OS X, an alias is a pointer file that allows you to quickly open the files, folders, servers, or applications used most often.When you double-click an alias, the operating system finds the file it references and opens it.
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.
The aliases in Figure 7.9 are for the tcsh shell, and several of them make use of specific advanced features of that shell (see man tcsh for all of the available features). For example, the alias in Figure 7.9 called line expects two arguments (indicated by!:1 and!:2 ), while the alias called ll takes all of its arguments (indicated. See full list on dummies.com.
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]
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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.
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 number
62 6F 6F 6B 00 00 00 00 6D 61 72 6B 00 00 00 00
which is in ASCIIbook␀␀␀␀mark␀␀␀␀
(␀ representing the Null character).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]
![Make Alias For Mac Make Alias For Mac](/uploads/1/2/6/6/126617953/351284858.jpg)
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
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]
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.
![Mac Mac](/uploads/1/2/6/6/126617953/705780375.jpg)
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 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
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Alias_(Mac_OS)&oldid=968846669'
An alias is a tiny file that automatically opens the file that it represents. Although an alias is technically an icon, it’s actually an icon that opens another icon automatically. You can put aliases in convenient places, such as on the Desktop, to help you easily open programs and files that you access often.
In effect, Microsoft stole the alias feature from Apple (if you’ve used Windows, you may know aliases as shortcuts). However, aliases usually don’t break when you move or rename the original file; shortcuts do.
An alias is different from a duplicated file. For example, the Microsoft Word 2004 application uses 19.4 megabytes (MB) of disk space. A duplicate of Microsoft Word 2004 would give you two files, each requiring nearly 20 megabytes of space on your hard drive. An alias of Microsoft Word 2004, on the other hand, uses a mere 52 kilobytes (KB).
Aliases can open any file or folder on any disk from anywhere else on any disk — which is a very good trick. But aliases are great for many other reasons:
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- Convenience: Aliases enable you to make items appear to be in more than one place, which on many occasions is exactly what you want to do. For example, keeping an alias of your word processor on your Desktop and another on the Dock is convenient. You may even want a third alias of it in your Documents folder for quick access. Aliases enable you to open your word processor quickly and easily without navigating into the depths of your Applications folder each time that you need it.
- Flexibility and organization: You can create aliases and store them anywhere on your hard disk to represent the same document in several different folders. This is a great help when you need to file a document that can logically be stored in any one of several files. For example: If you write a memo to Fred Smith about the Smythe Marketing Campaign to be executed in the fourth quarter, which folder does the document go in? Smith? Smythe? Marketing? Memos? 4th Quarter? Correct answer: With aliases, it can go in all of them if you like. Then you can find the memo wherever you look, instead of guessing which folder you filed it in.
With aliases, it doesn’t matter. You can put the actual file in any folder and then create aliases of the file, placing them in any other applicable folder.
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- Integrity: Some programs must remain in the same folder as their supporting files and folders. Many Classic programs, for example, don’t function properly unless they’re in the same folder as their dictionaries, thesauruses, data files (for games), templates, and so on. Thus, you can’t put the icon for those programs on the Desktop without impairing their functionality. An alias lets you access a program like that from anywhere on your hard disk.
Creating aliases
When you create an alias, its icon looks the same as the icon that it represents, but the suffix alias is tacked onto its name and a tiny arrow called a badge appears in the lower-left corner of its icon. Figure 1 shows both an alias and its parent icon (that is, the icon that opens if you open the alias).
Figure 1: An alias icon (right) and its parent.
To create an alias for an icon, do one of the following:
- Click the parent icon and choose File –> Make Alias.
- Click the parent icon and press Command+L.
- Click any file or folder, press and hold down the Command and Option keys, and then drag the file or folder while continuing to hold down the Command and Option keys.
Presto! An alias appears where you release the mouse button. Better still, aliases created this way don’t have that pesky alias suffix tacked onto them.
- Click an icon while holding down the Control key and then choose the Make Alias command from the contextual menu that appears.
- The alias appears in the same folder as its parent.
Deleting aliases
Deleting an alias is an easy chore. To delete an alias, simply drag it onto the Trash icon on the Dock. That’s it! You can also Control-click it and choose Move to Trash from the contextual menu that appears, or select the icon and use the keyboard shortcut Command+Delete.
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Deleting an alias does not delete the parent item. (If you want to delete the parent item, you have to go hunt it down and kill it yourself.)
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Hunting down an alias’ parent
Suppose that you create an alias of a file, and later you want to delete both the alias and its parent file — but you can’t find the parent file? What do you do? Well, you can use the Finder’s Find function (try saying that three times real fast) to find it, but here are three faster ways to find the parent icon of an alias:
- Select the alias icon and choose File –> Show Original.
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- Select the alias icon and use the keyboard shortcut Command+R.
How To Open Alias Files
- Control-click the alias icon and choose Show Original from the contextual menu.