使用R函数download.file从互联网下载数据时，无法打开目标文件

url <- "http://example.com/datafile.csv"
download.file(url, destfile = "datafile.csv", method = "auto")

url <- "http://example.com/datafile.csv"
download.file(url, destfile = "datafile.csv", method = "curl")

url <- "https://example.com/datafile.csv"
download.file(url, destfile = "datafile.csv", method = "auto", ssl.verifypeer = FALSE)

url <- "https://example.com/datafile.csv"
download.file(url, destfile = "datafile.csv", method = "auto", quiet = TRUE, ssl.verifypeer = FALSE)

# 检查文件是否下载成功
if(file.exists("datafile.csv")) {
  print("文件下载成功")
} else {
  print("文件下载失败")
}