AmigaDOS is the disk operating system of the AmigaOS, which includes file systems, file and directory manipulation, the command-line interface, and file redirection.
In AmigaOS 1.x, AmigaDOS is based on a TRIPOS port by MetaComCo, written in BCPL. BCPL does not use native pointers, so the more advanced functionality of the operating system was difficult to use and error-prone. The third-party AmigaDOS Resource Project (ARP, formerly the AmigaDOS Replacement Project), a project begun by Amiga developer Charlie Heath, replaced many of the BCPL utilities with smaller, more sophisticated equivalents written in C and assembler, and provided a wrapper library, arp.library. This eliminated the interfacing problems in applications by automatically performing conversions from native pointers (such as those used by C or assembler) to BCPL equivalents and vice versa for all AmigaDOS functions.
From AmigaOS 2.x onwards, AmigaDOS was rewritten in C, retaining 1.x compatibility where possible. Starting with AmigaOS 4, AmigaDOS abandoned its legacy with BCPL. Starting from AmigaOS 4.1, AmigaDOS has been extended with 64-bit file-access support.
Console The Amiga console is a standard Amiga virtual device, normally assigned to CON: and driven by console.handler. It was developed from a primitive interface in AmigaOS 1.1, and became stable with versions 1.2 and 1.3, when it started to be known as AmigaShell and its original handler was replaced by newconsole.handler (NEWCON:).
The console has various features that were considered up to date when it was created in 1985, like command template help, redirection to null ("NIL:"), and ANSI color terminal. The new console handler – which was implemented in release 1.2 – allows many more features, such as command history, pipelines, and automatic creation of files when output is redirected. When TCP/IP stacks like AmiTCP were released in the early 1990s, the console could also receive redirection from Internet-enabled Amiga device handlers (e.g., TCP:, ).
Unlike other systems originally launched in the mid-1980s, AmigaDOS does not implement a proprietary character set; the developers chose to use the ANSI–ISO standard ISO-8859-1 (Latin 1), which includes the ASCII character set. As in Unix systems, the Amiga console accepts only linefeed ("LF") as an end-of-line ("EOL") character. The Amiga console has support for accented characters as well as for characters created by combinations of 'dead keys' on the keyboard.
Syntax of AmigaDOS commands This is an example of typical AmigaDOS command syntax:
1> Dir DF0:
Without entering the directory tree, this shows the content of a directory of a floppy disk and lists subdirectories as well.
1> Dir SYS: ALL
The argument "ALL" causes the command to show the entire content of a volume or device, entering and expanding all directory trees. "SYS:" is a default name that is assigned to the boot device, regardless of its physical name.
Command redirection AmigaDOS can redirect the output of a command to files, pipes, a printer, the null device, and other Amiga devices.
1> Dir > SPEAK: ALL
Redirects the output of the "dir" command to the speech synthesis handler. The colon character ":" indicates that SPEAK: points to an AmigaDOS device. While a typical use for a device is file systems, special-purpose device names such as this are commonly used in the system.
Command template AmigaDOS commands are expected to provide a standard "template" that describes the arguments they can accept. This can be used as a basic "help" feature for commands, although third-party replacement console handlers and shells, such as Bash or Zshell (ported from Unix), or KingCON often provide more verbose help for built-in commands.
On requesting the template for the command "Copy", the following output is obtained:
1> Copy ? FROM, TO/A, ALL/S, QUIET/S
This string means that the user must use this command in conjunction with FROM and TO arguments, where the latter is compulsory (). The argument keywords ALL and QUIET are switches () and change the results of the command Copy (ALL causes all files in a directory to be copied, while QUIET will cause the command to generate no output).
By reading this template, a user can know that the following syntax is acceptable for the command:
1> Copy DF0:Filename TO DH0:Directory/Filename
Breaking commands and pausing console output A user can terminate a program by invoking the key combination or . Pressing or any printing character on the keyboard suspends the console output. Output may be resumed by pressing the key (to delete all of the input) or by pressing (which will cause the input to be processed as a command as soon as the current command stops running).
Wildcard characters Like other operating systems, AmigaDOS also provides wildcard characters that are substitutes for any character or any sequence of random characters in a string. Here is an example of wildcard characters in AmigaDOS commands:
1> Dir #?.info
searches the current directory for any file containing ".info" at its end as suffix, and displays only these files in the output.
The parsing of this is as follows. The "?" wildcard indicates "any character". Prefixing this with a "#" indicates "any number of repetitions". This can be viewed as analogous to the regular expression ".*".
Filename characters AmigaDOS uses '/' as a directory separator and ':' as a root reference, so filenames look like: SYS:subdir/anotherdir/filename.info. :objectname is an object in the root directory, a leading '/' refers to the parent directory so //mary is equivalent to the Unix path ../../mary.
Scripting AmigaDOS also has the feature of dealing with batch programming, which it calls "script" programming, and has a number of commands such as Echo, If, Then, EndIf, Val, and Skip to deal with structured script programming. Scripts are text-based files and can be created with AmigaDOS's internal text editor program, called Ed (unrelated to Unix's Ed), or with any other third-party text editor. To invoke a script program, AmigaDOS uses the command Execute.
1> Execute myscript
This executes the script called "myscript".
This method of executing scripts keeps the console window busy until the script has finished its scheduled job. Users cannot interact with the console window until the script ends or until they interrupt it.
While: 1> Run Execute myscript
The AmigaDOS command Run launches any DOS command or any kind of program in the background and immediately returns to the console prompt for further input.
Protection bits Protection bits are flags that files, links and directories have in the filesystem. To change them one can either use the command Protect, or use the Information entry from the Icons menu in Workbench on selected files. AmigaDOS supports the following set of protection bits (abbreviated as HSPARWED): H = Hold (reentrant commands with the P-bit set will automatically become resident on first execution. Requires E, P and R bits set to work. Does not mean "Hide". See below.) S = Script (Batch file. Requires E and R bits set to work.) If this protection bit is set on, then AmigaDOS is able to recognize and automatically run a script by simply invoking its name. Without S bit scripts can still be launched using the Execute command. P = Pure (indicates reentrant commands that can be made resident in RAM and then no longer need to be loaded any time from flash drives, hard disks or any other media device. Requires E and R bits set to work.) A = Archive (Archived bit, used by various backup programs to indicate that a file has been backed up) R = Read (Permission to read the file, link or content of directory) W = Write (Permission to write the file, link or inside a directory) E = Execute (Permission to execute the file or enter the directory. All commands need this bit set, or they won't run. Requires R bit set to work.) D = Delete (Permission to delete the file, link or directory)
The H-bit has often been misunderstood to mean "Hide". In Smart File System (SFS) files and directories with H-bit set are hidden from the system. It is still possible access hidden files but they don't appear in any directory listings.
Demonstration of H-bit in action: AmigaPrompt> which list Workbench:C/List AmigaPrompt> list workbench:c/list Directory "workbench:c" on Thursday 30-Oct-08 list 6464 --p-rwed 25-Feb-02 22:30:00 1 file - 14 blocks used AmigaPrompt> which list Workbench:C/List AmigaPrompt> protect workbench:c/list +h AmigaPrompt> which list Workbench:C/List AmigaPrompt> list workbench:c/list Directory "workbench:c" on Thursday 30-Oct-08 list 6464 h-p-rwed 25-Feb-02 22:30:00 1 file - 14 blocks used AmigaPrompt> which list RES list
Notice how the list command becomes resident after execution when the H-bit is set.
Local and global variables As any other DOS, Amiga deals with environment variables as used in batch programming.
There are both global and local variables, and they are referred to with a dollar sign in front of the variable name, for example $myvar. Global variables are available system-wide; local variables are only valid in the current shell. In case of name collision, local variables have precedence over global variables. Global variables can be set using the command SetEnv, while local variables can be set using the command Set. There are also the commands GetEnv and Get that can be used to print out global and local variables.
The examples below demonstrate simple usage:
1> setenv foo blapp 1> echo $foo blapp 1> set foo bar 1> echo $foo bar 1> getenv foo blapp 1> get foo bar 1> type ENV:foo blapp 1> setenv save foo $foo 1> type ENV:foo bar 1> type ENVARC:foo bar If the save flag of the SetEnv command is set, this variable is saved permanently in ENVARC: and remains available even after the current session has ended or the system has been restarted.
Global variables are kept as files in ENV:, and optionally saved on disk in ENVARC: to survive reboot and power cycling. ENV: is by default an assign to RAM:Env, and ENVARC: is an assign to SYS:Prefs/Env-archive where SYS: refers to the boot device. On bootup, the content of ENVARC: is copied to ENV: for accessibility.
When programming AmigaDOS scripts, one must keep in mind that global variables are system-wide. All script-internal variables shall be set using local variables, or one risks conflicts over global variables between scripts. Also, global variables require filesystem access, which typically makes them slower to access than local variables.
Since ENVARC: is also used to store other system settings than just string variables (such as system settings, default icons and more), it tends to grow large over time, and copying everything over to ENV: located on RAM disk becomes expensive. This has led to alternative ways to set up ENV: by using dedicated ramdisk handlers that only copy files over from ENVARC: when the files are requested. Examples of such handlers are and.
An example demonstrating creative abuse of global variables as well as Lab and Skip is the AmigaDOS variant of the infamous GOTO.
Case sensitivity AmigaDOS is in general case-insensitive. Indicating a device as "Dh0:", "DH0:" or "dh0:" always refers to the same partition; however, for file and directory names, this is filesystem-dependent, and some filesystems allow case sensitivity as a flag upon formatting. An example of such a file system is Smart File System. This is very convenient when dealing with software ported over from the mostly case-sensitive Un*x world, but causes much confusion for native Amiga applications, which assume case insensitivity. Advanced users will hence typically only use the case sensitivity flag for file systems used for software originating from Un*x.