Prompt
What is this?
Prompt makes it easy to build slick command-line applications with Tab Completion, Command History, and Built-in Help
Installation
gem install prompt
An example
Commands are defined with a Sinatra-inspired DSL:
require 'prompt'
extend Prompt::DSL
desc "Move"
variable :direction, "A cardinal direction", %w(north east south west)
command "go :direction", "Walk in the specified direction" do |direction|
puts "You walked #{direction} and were eaten by a grue."
end
desc "Interact"
command "look", "Look around" do
puts "You're in a dark room."
end
command "say :something", "Say something" do |something|
puts "You say '#{something}'"
end
Prompt::Console.start
Tab completion
Tab completion is hooked up automatically after you define your commands and variables
$ my_app
> g<TAB>
> go <TAB>
go east go north go south go west
> go n<TAB>
> go north
Command history
Command history is enabled automatically. You can scroll through the history with the UP and DOWN keys. You can search the history with CTRL-R.
You can preserve the history between runs by specifying a history filename when starting the console
history_file = File.join(ENV["HOME"], ".my-history")
Prompt::Console.start history_file
Built-in help
The help
command is built-in. It will print all of the commands that you've defined in your app.
$ my_app
> help
Console commands
help -v
help
exit
Move
go <direction> Walk in the specified direction
Interact
look Look around
say <something> Say something
Grouping commands
You can put commands in logical groups. This only affects how help is printed.
desc "Taco commands"
command ...
command ...
desc "Burger commands"
command ...
Using Variables
Variables can be used in a command.
command "name :first :last" do |first, last|
puts "Hi #{first} #{last}"
end
Here, the variables are named first
and last
. Their values are be passed as arguments to the command's block, in the order in which they appear.
Defining variables
It's not necessary to define a variable before using it in a command, but doing so will allow you to provide a useful description and valid values for the variable.
variable :name, "Description"
Specifying a static list of valid values
You can specify a static list of valid values for a variable. These will be expanded when using tab completion.
variable :name, "Description", %w(value1 value2)
Specifying a dynamic list of valid values
Instead of specifying a static list, you can specify a block that will dynamically return a list of valid values for a variable. These will be expanded when using tab completion.
dynamic_variable :file, "JPG file" do
Dir.glob "*.jpg"
end
Configuration options
The default prompt "> "
can be changed before starting the console.
Prompt::Console.prompt = "#{Dir.pwd}> "