在Linux中运行R脚本时等待用户输入

我已将代码添加到单独的函数中并使用系统(“stty -echo”)但未成功.
为什么会发生这种情况,可以做些什么？
(执行命令：Rscript test.R)

require(Biostrings)
read_value <- function(prompt_text = "",prompt_suffix = getOption("prompt"),coerce_to= "character")
{
  prompt <- paste(prompt_text,prompt_suffix)
  system("stty -echo")
  as(readline(prompt),coerce_to)
 }

prints<-function()
{ opt<-as.character(readline(prompt = "Enter parameter values: "))
  system("stty -echo")
  i<-1
  while ((i<=5))
    { if (i==1)
       { expr.filename <- as.character(readline(prompt = "Expression file name: "))
         tryCatch( {expr.file<-read.table(expr.filename)},error=function(e)
             {print("ERROR : Enter valid filename!") return })
       }
      if (i==2)
      {  system("stty -echo")
       fasta.filename <- as.character(readline(prompt = "Fasta file name: "))
       tryCatch( {sequence_data<-read.DNAStringSet(fasta.filename)},error=function(e) 
                {print("ERROR : Enter valid filename!")  return })
      }
     #missing piece of code
    i<-i+1
}