Question

我想写一个字符串，其中包含R（\n）的常用新行字符到数据库表的列中。

如何将新行转换为特定于操作系统的表示形式（Windows = CR / LF，Linux = LF，Mac = CR ...）？

我了解到R没有提供特定于操作系统的表示，所以我必须找到一个解决方法：

任何打印/ cat字符串的试验都会失败：

msg <- "I want to have \n a new line"
cat(msg)
# I want to have 
#  a new line

out <- capture.output(cat(msg))
out
# a vector with two elements (one for each row but no new line characters anymore)
# [1] "I want to have " " a new line"

paste(out, collapse = "\n")   # how could I inject the correct new line characters here?
# [1] "I want to have \n a new line"

# welcome endless-loop :-)

有没有办法让R在字符串中从\n创建正确的换行符？

PS：我正在使用内置的tcltk软件包和puts，但我总是以R＆＃34; resverting＆＃34;结束。新行到\n ... 另一个＆＃34;作弊＆＃34;可以用引号括起\n来读取它，好像它是一行一样。到目前为止我不知道这是如何起作用的......

Answer 1

在R中正确设置新行代码的一种方法是查询操作系统。由于OS X和Linux的行为方式相同，因此确定操作系统是否为Windows是一个问题。一种方法是按如下方式查询OS环境变量。

if(substr(Sys.getenv("OS"),1,7) == "Windows") {
    # set Windows newline
  newLine <- "\r\n"
}
else {
    # set non-Windows newline
    newLine <- "\n"
}

接下来使用paste()和newLine对象为操作系统生成新行的正确字符。

paste("my text string on a line",newline,sep="")

的问候，

Len

Answer 2

在这里，您可以找到我的最终实现，作为已接受答案的可能替代方案：

# Returns the operating system specific new line character(s):
# CR LF on Windows, else only LF...
# Simlar to Microsofts .Net "Environment.NewLine"
platform.NewLine <- function() {

  is.windows <- grepl(tolower(.Platform$OS.type), "windows", fixed = TRUE)

  if (is.windows) {
    newline <- "\r\n"
  } else {
    newline <- "\n"
  }

  sys.name <- Sys.info()["sysname"]
  is.windows.2nd.opinion <- grepl(tolower(sys.name), "windows", fixed = TRUE)

  if (is.windows != is.windows.2nd.opinion)
    warning("R seems to run on Windows OS but this could not be recognized for sure")

  return(newline)
}

# Usage (examples) ------------------------------------------------------------------------------------------------

newline <- platform.NewLine()

# "print" shows the "symbolic" names (escape codes)
print(paste("Line1", "Line2", sep = newline))
# [1] "Line1\r\nLine2"
# uses "\n" or "\r\n" depending on your OS

# "cat" applies the newline escape codes to the output
cat(paste("Line1", "Line2", sep = newline))
# Line1
# Line2

使用特定于操作系统的换行符（CRLF，LF，CR）构建字符串，以将其写入数据库表列

2 个答案: