preProcess: Download, checksum, extract files

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Download, checksum, extract files

Description

This does downloading (via downloadFile), checksumming (Checksums), and extracting from archives (extractFromArchive), plus cleaning up of input arguments (e.g., paths, function names). This is the first stage of three used in prepInputs.

Usage

preProcessParams(n = NULL)

preProcess(
  targetFile = NULL,
  url = NULL,
  archive = NULL,
  alsoExtract = NULL,
  destinationPath = getOption("reproducible.destinationPath", "."),
  fun = NULL,
  dlFun = NULL,
  quick = getOption("reproducible.quick"),
  overwrite = getOption("reproducible.overwrite", FALSE),
  purge = FALSE,
  verbose = getOption("reproducible.verbose", 1),
  .tempPath,
  .callingEnv = parent.frame(),
  ...
)

Arguments

n	Number of non-null arguments passed to preProcess. E.g., passing n = 1 returns combinations with only a single non-NULL parameter. If NULL (default), all parameter combinations are returned.
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().
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.
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().
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.
fun	Optional. If specified, this will attempt to load whatever file was downloaded during preProcess via dlFun. This can be either a function (e.g., sf::st_read), character string (e.g., "base::load"), NA (for no loading, useful if dlFun already loaded the file) or if extra arguments are required in the function call, it must be a call naming targetFile (e.g., sf::st_read(targetFile, quiet = TRUE)) as the file path to the file to load. See details and examples below.
dlFun	Optional "download function" name, such as "raster::getData", which does custom downloading, in addition to loading into R. Still experimental.
quick	Logical. This is passed internally to Checksums() (the quickCheck argument), and to Cache() (the quick argument). This results in faster, though less robust checking of inputs. See the respective functions.
overwrite	Logical. Passed to writeTo (possibly inside postProcess) and postProcess.
purge	Logical or Integer. 0/FALSE (default) keeps existing CHECKSUMS.txt file and prepInputs will write or append to it. 1/TRUE will deleted the entire CHECKSUMS.txt file. Other options, see details.
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
.tempPath	Optional temporary path for internal file intermediate steps. Will be cleared on.exit from this function.
.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.

Value

A list with 5 elements: checkSums (the result of a Checksums after downloading), dots (cleaned up ..., including deprecated argument checks), fun (the function to be used to load the preProcessed object from disk), and targetFilePath (the fully qualified path to the targetFile).

Combinations of targetFile, url, archive, alsoExtract

Use preProcessParams() for a table describing various parameter combinations and their outcomes.

* If the url is a file on Google Drive, checksumming will work even without a targetFile specified because there is an initial attempt to get the remove file information (e.g., file name). With that, the connection between the url and the filename used in the ‘CHECKSUMS.txt’ file can be made.

Author(s)

Eliot McIntire

Examples

# preProcess() needs no url: a file already on disk is checksummed, placed in
# destinationPath, and (with fun = NA) reported rather than loaded.
dPath <- file.path(tempdir(), "preProcessExample")
shp <- system.file("ex/luxSmall/luxSmall.shp", package = "reproducible")

out <- preProcess(targetFile = shp, destinationPath = dPath, fun = NA)
basename(out$targetFilePath)

# A CHECKSUMS.txt is written, which is what makes a second call cheap.
dir(dPath)

unlink(dPath, recursive = TRUE)

reproducible documentation built on Aug. 26, 2026, 1:07 a.m.