ask: Ask questions to the user, at the command line, and get the...
In gaborcsardi/ask: Friendly Command Line Interface Tools

Description Usage Arguments Details Value Question types ‘input’ type ‘confirm’ type ‘choose’ type ‘checkbox’ type ‘constant’ type Conditional execution Examples

View source: R/ask.R

Ask questions to the user, at the command line, and get the answers

1	ask(..., .prompt = yellow(paste0(symbol$pointer, " ")))

`...`	Questions to ask, see details below.
`.prompt`	Prompt to prepend to all questions.

Ask a series of questions to the user, and return all results together in a list.

The ask function takes named arguments only:

Each argument corresponds to a question to the user.
The name of the argument is the identifier of the question, the answer will have the same name in the result list.
Each argument is a function call. The name of the function is the type of the question. See question types below.
Questions are asked in the order they are given. See ‘Conditional execution’ below for more flexible workflows.

A named list with the answers.

input: One line of text input.
confirm: A yes-no question, ‘y’ and ‘yes’ are considered as positive, ‘n’ and ‘no’ as negative answers (case insensitively).
choose: Choose one item form multiple items.
checkbox: Select multiple values from a list.
constant: Not a question, it defines constants.

1 2	input(message, default = "", filter = NULL, validate = NULL, when = NULL)

message: The message to print.
default: The default vaue to return if the user just presses enter.
filter: If not NULL, then it must be a function, that is called to filter the entered result.
validate: If not NULL, then it must be a function that is called to validate the input. The function must return TRUE for valid inputs and an error message (character scalar) for invalid ones.
when: See ‘Conditional execution’ below.

1	confirm(message, default = TRUE, when = NULL)

message: The message to print.
default: The default answer if the user just presses enter.
when: See ‘Conditional execution’ below.

1	choose(message, choices, default = NA, when = NULL)

message: Message to print.
choices: Possible choices, character vector.
default: Index or value of the default choice (if the user hits enter, or NA for no default. Values are matched using partial matches via pmatch.
when: See ‘Conditional execution’ below.

1	checkbox(message, choices, default = numeric(), when = NULL)

message: Message to print.
choices: Possible choices, character vector.
default: Indices or values of default choices. values are matches using partial matches via pmatch.
when: See ‘Conditional execution’ below.

1	constant(value = constant_value, when = NULL)

constant_value: The constant value. Note that the argument must be named.
when: See ‘Conditional execution’ below.

The when argument to a question can be used for conditional execution of questions. If it is given (and not NULL), then it must be a function. It is called with the answers list up to that point, and it should return TRUE or FALSE. For TRUE, the question is shown to the user and the result is inserted into the answer list. For FALSE, the question is not shown, and the answer list is not chagned.

## Not run: 
ask(
  name =  input("What is your name?"),
  cool = confirm("Are you cool?"),
  drink = choose("Select your poison!", c("Beer", "Wine")),
  language = checkbox("Favorite languages?", c("C", "C++", "Python", "R"))
)

## End(Not run)