Report result code for each URL when downloading files simultaneously…

… via

download.file().  Limit the number of concurrently open files and concurrent
downloads.


git-svn-id: https://svn.r-project.org/R/trunk@87084 00db46b3-68df-0310-9c12-caf00c1e9a41

src/library/utils/man/download.file.Rd

@@ -1,6 +1,6 @@
 % File src/library/utils/man/download.file.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2022 R Core Team
+% Copyright 1995-2024 R Core Team
 % Distributed under GPL 2 or later
 
 \name{download.file}
@@ -274,7 +274,12 @@ download.file(url, destfile, method, quiet = FALSE, mode = "w",
  An (invisible) integer code, \code{0} for success and non-zero for
  failure. For the \code{"wget"} and \code{"curl"} methods this is the
  status code returned by the external program. The \code{"internal"}
- method can return \code{1}, but will in most cases throw an error.
+ method can return \code{1}, but will in most cases throw an error. When
+ simultaneously downloading two or more files (see the \code{url} argument)
+ and download of at least one file succeeds, \code{0} is returned with
+ attribute \code{retvals}, which provides an integer vector of the same
+ length as \code{url} with a result code for each file (\code{0} for
+ success and non-zero for failure).
 
  What happens to the destination file(s) in the case of error depends
  on the method and \R{} version. Currently the \code{"internal"},