| % File src/library/base/man/readline.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2009 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{readline} |
| \title{Read a Line from the Terminal} |
| \concept{waiting for input} |
| \concept{user prompting} |
| \usage{ |
| readline(prompt = "") |
| } |
| \alias{readline} |
| \arguments{ |
| \item{prompt}{the string printed when prompting the user for input. |
| Should usually end with a space \code{" "}.} |
| } |
| \description{ |
| \code{readline} reads a line from the terminal (in interactive use). |
| } |
| \details{ |
| The prompt string will be truncated to a maximum allowed length, |
| normally 256 chars (but can be changed in the source code). |
| |
| This can only be used in an \link{interactive} session. |
| } |
| \value{ |
| A character vector of length one. Both leading and trailing |
| spaces and tabs are stripped from the result. |
| |
| In non-\link{interactive} use the result is as if the response was |
| RETURN and the value is \code{""}. |
| } |
| \seealso{ |
| \code{\link{readLines}} for reading text lines from connections, |
| including files. |
| } |
| \examples{ |
| fun <- function() { |
| ANSWER <- readline("Are you a satisfied R user? ") |
| ## a better version would check the answer less cursorily, and |
| ## perhaps re-prompt |
| if (substr(ANSWER, 1, 1) == "n") |
| cat("This is impossible. YOU LIED!\n") |
| else |
| cat("I knew it.\n") |
| } |
| if(interactive()) fun() |
| } |
| \keyword{utilities} |