src/library/utils/R/unix/download.file.R

#  File src/library/utils/R/unix/download.file.R
#  Part of the R package, https://www.R-project.org
#
#  Copyright (C) 1995-2020 The R Core Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  https://www.R-project.org/Licenses/

download.file <-
    function(url, destfile, method, quiet = FALSE, mode = "w",
             cacheOK = TRUE, extra = getOption("download.file.extra"),
             headers = NULL, ...)
{
    destfile # check supplied
    method <- if (missing(method))
	getOption("download.file.method", default = "auto")
    else
        match.arg(method, c("auto", "internal", "libcurl", "wget", "curl", "lynx"))

    if(method == "auto") {
        if(length(url) != 1L || typeof(url) != "character")
            stop("'url' must be a length-one character vector");
        ## As from 3.3.0 all Unix-alikes support libcurl.
	method <- if(startsWith(url, "file:")) "internal" else "libcurl"
    }

    nh <- names(headers)
    if(length(nh) != length(headers) || any(nh == "") || anyNA(headers) || anyNA(nh))
	stop("'headers' must have names and must not be NA")

    switch(method,
	   "internal" = {
	       headers <- if(length(headers)) paste0(nh, ": ", headers, "\r\n", collapse = "")
	       status <- .External(C_download, url, destfile, quiet, mode,
				   cacheOK, headers)
	       ## needed for Mac GUI from download.packages etc
	       if(!quiet) flush.console()
	   },
	   "libcurl" = {
	       headers <- if(length(headers)) paste0(nh, ": ", headers)
	       status <- .Internal(curlDownload(url, destfile, quiet, mode,
						cacheOK, headers))
	       if(!quiet) flush.console()
	   },
	   "wget" = {
	       if(length(url) != 1L || typeof(url) != "character")
		   stop("'url' must be a length-one character vector");
	       if(length(destfile) != 1L || typeof(destfile) != "character")
		   stop("'destfile' must be a length-one character vector");
	       if(quiet) extra <- c(extra, "--quiet")
	       if(!cacheOK) extra <- c(extra, "--cache=off")
	       status <- system(paste("wget",
				      paste(extra, collapse = " "),
				      shQuote(url),
				      "-O", shQuote(path.expand(destfile))))
               if(status) stop("'wget' call had nonzero exit status")
	   },
	   "curl" = {
	       if(length(url) != 1L || typeof(url) != "character")
		   stop("'url' must be a length-one character vector");
	       if(length(destfile) != 1L || typeof(url) != "character")
		   stop("'destfile' must be a length-one character vector");
	       if(quiet) extra <- c(extra, "-s -S")
	       if(!cacheOK) extra <- c(extra, paste("-H", shQuote("Pragma: no-cache")))
	       status <- system(paste("curl",
				      paste(extra, collapse = " "),
				      shQuote(url),
				      " -o", shQuote(path.expand(destfile))))
               if(status) stop("'curl' call had nonzero exit status")
	   },
	   "lynx" =
	       stop("method 'lynx' is defunct", domain = NA))

    if(status) warning("download had nonzero exit status")

    invisible(status)
}

nsl <- function(hostname) .Call(C_nsl, hostname)