Download a remote file

downloadRemote(
  url,
  archive,
  targetFile,
  checkSums,
  dlFun = NULL,
  fileToDownload,
  messSkipDownload,
  destinationPath,
  overwrite,
  needChecksums,
  .tempPath,
  preDigest,
  alsoExtract = "similar",
  verbose = getOption("reproducible.verbose", 1),
  .callingEnv = parent.frame(),
  ...
)

Arguments

url

Optional character string indicating the URL to download from. If not specified, then no download will be attempted. If not entry exists in the CHECKSUMS.txt (in destinationPath), an entry will be created or appended to. This CHECKSUMS.txt entry will be used in subsequent calls to prepInputs or preProcess, comparing the file on hand with the ad hoc CHECKSUMS.txt. See table in preProcess().

archive

Optional character string giving the path of an archive containing targetFile, or a vector giving a set of nested archives (e.g., c("xxx.tar", "inner.zip", "inner.rar")). If there is/are (an) inner archive(s), but they are unknown, the function will try all until it finds the targetFile. See table in preProcess(). If it is NA, then it will not attempt to see it as an archive, even if it has archive-like file extension (e.g., .zip). This may be useful when an R function is expecting an archive directly.

targetFile

Character string giving the filename (without relative or absolute path) to the eventual file (raster, shapefile, csv, etc.) after downloading and extracting from a zip or tar archive. This is the file before it is passed to postProcess. The internal checksumming does not checksum the file after it is postProcessed (e.g., cropped/reprojected/masked). Using Cache around prepInputs will do a sufficient job in these cases. See table in preProcess().

checkSums

TODO

dlFun

Optional "download function" name, such as "raster::getData", which does custom downloading, in addition to loading into R. Still experimental.

fileToDownload

TODO

messSkipDownload

The character string text to pass to messaging if download skipped

destinationPath

Character string of a directory in which to download and save the file that comes from url and is also where the function will look for archive or targetFile. To prevent repeated downloads in different locations, the user can also set options("reproducible.destinationPathShared") to one or more local file paths to search for the file before attempting to download. Default for that option is NULL meaning do not search locally. The previous name options("reproducible.inputPaths") is still accepted as a backwards-compatible alias.

overwrite

Logical. Passed to writeTo (possibly inside postProcess) and postProcess.

needChecksums

Logical indicating whether to generate checksums. ## TODO: add overwrite arg to the function?

.tempPath

Optional temporary path for internal file intermediate steps. Will be cleared on.exit from this function.

preDigest

The list of preDigest that comes from CacheDigest of an object

alsoExtract

Which files to fetch or extract in addition to targetFile. Spatial data rarely arrives as one file – a shapefile is five or six, and a raster often has a .aux.xml, .ovr or .tfw alongside carrying its attribute table, overviews or georeferencing – so this controls how much of that company comes along.

The default depends on where the files are coming from, because "everything" only means something when a container bounds it:

`alsoExtract`	from an `archive`	from a `url`
`NULL` (default)	every file in the archive	as for `"similar"`
`"similar"`	files sharing `targetFile`'s name without its extension	same, discovered by listing the remote directory
`NA` or `"none"`	`targetFile` only	`targetFile` only
a character vector	those files only	those files only

An archive bounds what "all files" can mean, so NULL extracts all of it. A url has no such bound – the server may hold thousands of unrelated files – so NULL there means targetFile and its companions, never the whole remote directory.

Each element of a character vector may also be a regular expression: if an element does not match any archive member literally (by relative path or basename), it is passed to grep() against the archive's file list and all matching members are extracted. For example, alsoExtract = "CMD_sm|CMD_sp" extracts every file whose name contains CMD_sm or CMD_sp. See table in preProcess().

verbose

Numeric, -1 silent (where possible), 0 being very quiet, 1 showing more messaging, 2 being more messaging, etc. Default is 1. Above 3 will output much more information about the internals of Caching, which may help diagnose Caching challenges. Can set globally with an option, e.g., options('reproducible.verbose' = 0) to reduce to minimal

.callingEnv

The environment where the function was called from. Used to find objects, if necessary.

...

Additional arguments passed to postProcess() and Cache(). Since ... is passed to postProcess(), these will ... will also be passed into the inner functions, e.g., cropInputs(). Possibly useful other arguments include dlFun which is passed to preProcess. See details and examples.