R/download-file.R

In runonce: Run Once and Save Result

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url_basename <- function(url) {
  basename(urltools::path(url))
}

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#' Download once
#'
#' Download file if does not exist yet.
#'
#' @param url URL of file to be downloaded.
#' @param dir Directory where to download the file.
#' @param fname Base name of the downloaded file (`dir` will be prefixed).
#' @param overwrite Whether to overwrite? Default is `FALSE`.
#' @param mode See parameter of [download.file()].
#'   Default of "wb" seems useful for Windows systems.
#' @inheritDotParams utils::download.file -url -destfile -mode
#'
#' @return Path to the downloaded (or existing) file.
#' @export
#'
#' @examples
#' download_file("https://github.com/privefl.png")
#' download_file("https://github.com/privefl.png")
#' download_file("https://github.com/privefl.png", overwrite = TRUE)
#'
download_file <- function(url,
                          dir = tempdir(),
                          fname = url_basename(url),
                          overwrite = FALSE,
                          mode = "wb",
                          ...) {

  bigassertr::assert_dir(dir)
  fname <- file.path(dir, fname)

  if (overwrite || !file.exists(fname))
    utils::download.file(url, destfile = fname, mode = mode, ...)

  fname
}

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