使R等待控制台输入? [英] Make R wait for console input?

问题描述

有没有办法让R在继续之前先等待控制台输入? 假设我在一个名为run.R的主脚本中提供了两个这样的脚本:

Is there a way to make R wait for console input before continuing? Let's say I source two scripts like this in a main script called run.R:

# some more R Code here

source("script1.R")
source("script2.R")

# some more R Code there

Script1包含一些readLine语句，要求用户输入用户名. 不幸的是，如果我只运行整个run.R文件，R不会等待输入用户名.它在输入用户名之前启动script2.R，这会导致错误，因为第二个脚本需要用户名.

Script1 contains some readLine statement that asks the user for a username. Unfortunately if I just run the entire run.R file R doesn't wait for the username to be entered. It starts script2.R before the username is entered which leads to an error because the 2nd script needs the username.

我使用R Studio的.rs.askForPassword有一个丑陋的解决方法，它实际上等待输入，但包含密码.密码很酷，但用户名却不那么酷.加上它是RStudio功能，而不是R.

I have an ugly workaround for this using R Studio's .rs.askForPassword which actually waits for the the input, but covers the password. Which is cool for passwords, but not so much for usernames. Plus it's an RStudio feature, not R.

推荐答案

尝试使用scan函数.

这是test.R文件:

y <- 2
cat('y=',y)
cat("\nEnter username")
x <- scan(what=character(),nmax=1,quiet=TRUE)
"ala ma kota"
y <- 2*2
cat('y=',y)
cat('\nx=',x)

然后运行此命令:

> source("test.R")
y= 2
Enter username
1: login
y= 4
x= login

-编辑- 要仅读取一个字符，请运行以下命令:

--edit-- To read only one character quietly run this:

> x <- scan(what=character(),nmax=1,quiet=TRUE)
1: username
> x
[1] "username"

what设置类型，nmax设置要读取的最大元素数，并且quiet确定是否打印一行，说明已读取多少项.

what sets the type, nmax sets the maximal numbers of elements to read and quiet determine if print a line, saying how many items have been read.

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