R download.file() rename the downloaded file, if the filename already exists - r

Question

In R, I am trying to download files off the internet using the download.file() command in a simple code (am complete newbie). The files are downloading properly. However, if a file already exists in the download destination, I'd wish to rename the downloaded file with an increment, as against an overwrite which seems to be the default process.
nse.url = "https://www1.nseindia.com/content/historical/DERIVATIVES/2016/FEB/fo04FEB2016bhav.csv.zip"
nse.folder = "D:/R/Download files from Internet/"
nse.destfile = paste0(nse.folder,"fo04FEB2016bhav.csv.zip")
download.file(nse.url,nse.destfile,mode = "wb",method = "libcurl")
Problem w.r.t to this specific code: if "fo04FEB2016bhav.csv.zip" already exists, then get say "fo04FEB2016bhav.csv(2).zip"?
General answer to the problem (and not just the code mentioned above) would be appreciated as such a bottleneck could come up in any other situations too.

Answer 1

The function below will automatically assign the filename based on the file being downloaded. It will check the folder you are downloading to for the presence of a similarly named file. If it finds a match, it will add an incrementation and download to the new filename.
ekstroem's suggestion to fiddle with the curl settings is probably a much better approach, but I wasn't clever enough to figure out how to make that work.
download_without_overwrite <- function(url, folder)
{
filename <- basename(url)
base <- tools::file_path_sans_ext(filename)
ext <- tools::file_ext(filename)
file_exists <- grepl(base, list.files(folder), fixed = TRUE)
if (any(file_exists))
{
filename <- paste0(base, " (", sum(file_exists), ")", ".", ext)
}
download.file(url, file.path(folder, filename), mode = "wb", method = "libcurl")
}
download_without_overwrite(
url = "https://raw.githubusercontent.com/nutterb/redcapAPI/master/README.md",
folder = "[path_to_folder]")

Answer 2

Try this:
nse.url = "https://www1.nseindia.com/content/historical/DERIVATIVES/2016/FEB/fo04FEB2016bhav.csv.zip"
nse.folder = "D:/R/Download files from Internet/"
#Get file name from url, with file extention
fname.x <- gsub(".*/(.*)", "\\1", nse.url)
#Get file name from url, without file extention
fname <- gsub("(.*)\\.csv.*", "\\1", fname.x)
#Get xtention of file from url
xt <- gsub(".*(\\.csv.*)", "\\1", fname.x)
#How many times does the the file exist in folder
exist.times <- sum(grepl(fname, list.files(path = nse.folder)))
if(exist.times){
# if it does increment by 1
fname.x <- paste0(fname, "(", exist.times + 1, ")", xt)
}
nse.destfile = paste0(nse.folder, fname.x)
download.file(nse.url, nse.destfile, mode = "wb",method = "libcurl")
Issues
This approach will not work in cases where part of the file name already exists for example you have url/test.csv.zip and in the folder you have a file testABC1234blahblah.csv.zip. It will think the file already exists, so it will save it as test(2).csv.zip.
You will need to change the #How many times does the the file exist in folder part of the code accordingly.

Answer 3

This is not a proper answer and shouldn't be considered as such, but the comment section above was too small to write it all.
I thought the -O -n options to curl could be used to but now that I looked at it more closely it turned out that it wasn't implemented yet. Now wget automatically increment the filename when downloading a file that already exists. However, setting method="wget" doesn't work with download.file because you are forced to set the destination file name, and once you do that you overwrite the automatic file increments.
I like the solution that #Benjamin provided. Alternatively, you can use
system(paste0("wget ", nse.url))
to get the file through the system (provided that you have wget installed) and let wget handle the increment.