Afs Command

[Annette Fazzari]

Then, the rest of that sentence is just a list of stuff you could maybe possiblyuse the pattern for. Not very illuminating unless your use case happens to be inthat list. My pithy tagline for the Command pattern is:

Reflection systems in some languages let you work with the types in yourprogram imperatively at runtime. You can get an object that represents the classof some other object, and you can play with that to see what the type can do. Inother words, reflection is a reified type system.

If we want to support buttons that do nothing without having to explicitly checkfor NULL, we can define a command class whose execute() method does nothing.Then, instead of setting a button handler to NULL, we point it to that object.This is a pattern called NullObject.

This highlights a variation in how the Command pattern gets implemented. In somecases, like our first couple of examples, a command is a reusable object thatrepresents a thing that can be done. Our earlier input handler held on to asingle command object and called its execute() method anytime the right buttonwas pressed.

Here, the commands are more specific. They represent a thing that can be done ata specific point in time. This means that the input handling code will be creating an instance of this every time the player choosesa move. Something like:

The first time I implemented this in a level editor, I felt like a genius. I wasastonished at how straightforward it was and how well it worked. It takesdiscipline to make sure every data modification goes through a command, but onceyou do that, the rest is easy.

I wrote the examples this way because C++ has pretty limited support forfirst-class functions. Function pointers are stateless, functors are weird andstillrequire defining a class, and the lambdas in C++11 are tricky to work withbecause of manual memory management.

I say some ways here because building actual classes or structures forcommands is still useful even in languages that have closures. If your commandhas multiple operations (like undoable commands), mapping that to a singlefunction is awkward.

Some commands are stateless chunks of pure behavior like the JumpCommand in the first example. In cases like that, having more than one instance of that class wastes memory since all instances are equivalent. The Flyweight pattern addresses that.

The AWS Command Line Interface (AWS CLI) is a unified tool to manage your AWS services. With just one tool to download and configure, you can control multiple AWS services from the command line and automate them through scripts.

aws-shell is a command-line shell program that provides convenience and productivity features to help both new and advanced users of the AWS Command Line Interface. Key features include the following.

You speak a one-word command to a creature you can see within range. The target must succeed on a Wisdom saving throw or follow the command on its next turn. The spell has no effect if the target is undead, if it doesn't understand your language, or if your command is directly harmful to it.

Some typical commands and their effects follow. You might issue a command other than one described here. If you do so, the DM determines how the target behaves. If the target can't follow your command, the spell ends.

Halt: The target doesn't move and takes no actions. A flying creature stays aloft, provided that it is able to do so. If it must move to stay aloft, it flies the minimum distance needed to remain in the air.

At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, you can affect one additional creature for each slot level above 1st. The creatures must be within 30 feet of each other when you target them.

This module is part of ansible-core and included in all Ansibleinstallations. In most cases, you can use the shortmodule namecommand even without specifying the collections keyword.However, we recommend you use the Fully Qualified Collection Name (FQCN) ansible.builtin.command for easy linking to themodule documentation and to avoid conflicting with other collections that may havethe same module name.

If you want to run a command through the shell (say you are using , , and so on), you actually want the ansible.builtin.shell module instead. Parsing shell metacharacters can lead to unexpected commands being executed if quoting is not done correctly so it is more secure to use the ansible.builtin.command module when possible.

Check mode is supported when passing creates or removes. If running in check mode and either of these are specified, the module will check for the existence of the file and report the correct changed status. If these are not supplied, the task will be skipped.

A command-line interface (CLI) is a means of interacting with a computer program by inputting lines of text called command-lines. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive interface available with punched cards.

Alternatives to CLIs include GUIs (most notably desktop metaphors with a mouse pointer, such as Microsoft Windows), text-based user interface menus (such as DOS Shell and IBM AIX SMIT), and keyboard shortcuts.

Compared with a graphical user interface, a command-line interface requires fewer system resources to implement. Since options to commands are given in a few characters in each command line, an experienced user often finds the options easier to access. Automation of repetitive tasks is simplified by line editing and history mechanisms for storing frequently used sequences; this may extend to a scripting language that can take parameters and variable options. A command-line history can be kept, allowing review or repetition of commands.

A command-line system may require paper or online manuals for the user's reference, although often a help option provides a concise review of the options of a command. The command-line environment may not provide graphical enhancements such as different fonts or extended edit windows found in a GUI. It may be difficult for a new user to become familiar with all the commands and options available, compared with the icons and drop-down menus of a graphical user interface, without reference to manuals.

Operating system (OS) command-line interfaces are usually distinct programs supplied with the operating system. A program that implements such a text interface is often called a command-line interpreter, command processor or shell.

Examples of command-line interpreters include DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11, the various Unix shells (sh, ksh, csh, tcsh, zsh, Bash, etc.), CP/M's CCP, DOS' COMMAND.COM, as well as the OS/2 and the Windows CMD.EXE programs, the latter groups being based heavily on DEC's RSX-11 and RSTS CLIs. Under most operating systems, it is possible to replace the default shell program with alternatives; examples include 4DOS for DOS, 4OS2 for OS/2, and 4NT / Take Command for Windows.

Although the term 'shell' is often used to describe a command-line interpreter, strictly speaking, a 'shell' can be any program that constitutes the user-interface, including fully graphically oriented ones. For example, the default Windows GUI is a shell program named EXPLORER.EXE, as defined in the SHELL=EXPLORER.EXE line in the WIN.INI configuration file. These programs are shells, but not CLIs.

Some applications support a CLI, presenting their own prompt to the user and accepting command lines. Other programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file. In other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality. For example, all features of MATLAB, a numerical analysis computer program, are available via the CLI, whereas the MATLAB GUI exposes only a subset of features.

The command-line interface evolved from a form of communication conducted by people over teleprinter (TTY) machines. Sometimes these involved sending an order or a confirmation using telex. Early computer systems often used teleprinter as the means of interaction with an operator.

Early operating system CLIs were implemented as part of resident monitor programs, and could not easily be replaced. The first implementation of the shell as a replaceable component was part of the Multics time-sharing operating system.[1] In 1964, MIT Computation Center staff member Louis Pouzin developed the RUNCOM tool for executing command scripts while allowing argument substitution.[2] Pouzin coined the term shell to describe the technique of using commands like a programming language, and wrote a paper about how to implement the idea in the Multics operating system.[3] Pouzin returned to his native France in 1965, and the first Multics shell was developed by Glenda Schroeder.[2]

The first Unix shell, the V6 shell, was developed by Ken Thompson in 1971 at Bell Labs and was modeled after Schroeder's Multics shell.[4][5] The Bourne shell was introduced in 1977 as a replacement for the V6 shell. Although it is used as an interactive command interpreter, it was also intended as a scripting language and contains most of the features that are commonly considered to produce structured programs. The Bourne shell led to the development of the KornShell (ksh), Almquist shell (ash), and the popular Bourne-again shell (or Bash).[5]

Early microcomputers themselves were based on a command-line interface such as CP/M, DOS or AppleSoft BASIC. During the 1980s and 1990s, the introduction of the Apple Macintosh and of Microsoft Windows on PCs saw the command line interface as the primary user interface replaced by the Graphical User Interface.[6] The command line remained available as an alternative user interface, often used by system administrators and other advanced users for system administration, computer programming and batch processing.