RCurl: Display progress meter in Rgui - r

Question

Using R.exe or Rterm.exe, this gives an excellent progress meter.
page=getURL(url="ftp.wcc.nrcs.usda.gov", noprogress=FALSE)
In Rgui I am limited to:
page=getURL(url="ftp.wcc.nrcs.usda.gov",
noprogress=FALSE, progressfunction=function(down,up) print(down))
which gives a very limited set of download information.
Is there a way to improve this?

Answer 1

I start doubting that with standard R commands it is possible to reprint overwriting the current line, which is what RCurl does in non-GUI mode.
I am glad to tell that I was wrong. At least for a single line, \r can do the trick. In fact:
conc=function(){
cat(" abcd")
cat(" ABCD", '\n')
}
conc()
# abcd ABCD
But:
over=function(){
cat(" abcd")
cat("\r ABCD", "\n")
}
over()
# ABCD
That given, I wrote this progressDown function, which can monitor download status rewriting always on the same same line:
library(RCurl) # Don't forget
### Callback function for curlPerform
progressDown=function(down, up, pcur, width){
total=as.numeric(down[1]) # Total size as passed from curlPerform
cur=as.numeric(down[2]) # Current size as passed from curlPerform
x=cur/total
px= round(100 * x)
## if(!is.nan(x) && px>60) return(pcur) # Just to debug at 60%
if(!is.nan(x) && px!=pcur){
x= round(width * x)
sc=rev(which(total> c(1024^0, 1024^1, 1024^2, 1024^3)))[1]-1
lb=c('B', 'KB', 'MB', 'GB')[sc+1]
cat(paste(c(
"\r |", rep.int(".", x), rep.int(" ", width - x),
sprintf("| %g%s of %g%s %3d%%",round(cur/1024^sc, 2), lb, round(total/1024^sc, 2), lb, px)),
collapse = ""))
flush.console() # if the outptut is buffered, it will go immediately to console
return(px)
}
return(pcur)
}
Now we can use the callback with curlPerform
curlProgress=function(url, fname){
f = CFILE(fname, mode="wb")
width= getOption("width") - 25 # you can make here your line shorter/longer
pcur=0
ret=curlPerform(url=url, writedata=f#ref, noprogress=FALSE,
progressfunction=function(down,up) pcur<<-progressDown(down, up, pcur, width),
followlocation=T)
close(f)
cat('\n Download', names(ret), '- Ret', ret, '\n') # is success?
}
Running it with a small sample binary:
curlProgress("http://www.nirsoft.net/utils/websitesniffer-x64.zip", "test.zip")
the intermediate output at 60% is (no # protection):
|................................. | 133.74KB of 222.75KB 60%
where KB, will be adjusted to B, KB, MB, GB, based on total size.
Final output with success status, is:
|.......................................................| 222.61KB of 222.75KB 100%
Download OK - Ret 0
Note, the output line width is relative to R width option (which controls the maximum number of columns on a line) and can be customised changing the curlProgress line:
width= getOption("width") - 25
This is enough for my needs and solves my own question.

Answer 2

Here's a simple example using txtProgressBar. Basically, just do a HEAD request first to get the file size of the file you want to retrieve, then setup a txtProgressBar with that as its max size. Then you use the progressfunction argument to curlPerform to call setTxtProgressBar. It all works very nicely (unless there is no "content-length" header, in which case this code works by just not printing a progress bar).
url <- 'http://stackoverflow.com/questions/21731548/rcurl-display-progress-meter-in-rgui'
h <- basicTextGatherer()
curlPerform(url=url, customrequest='HEAD',
header=1L, nobody=1L, headerfunction=h$update)
if(grepl('Transfer-Encoding: chunked', h$value())) {
size <- 1
} else {
size <- as.numeric(strsplit(strsplit(h$value(),'\r\nContent-Type')[[1]][1],
'Content-Length: ')[[1]][2])
}
bar <- txtProgressBar(0, size)
h2 <- basicTextGatherer()
get <- curlPerform(url=url, noprogress=0L,
writefunction=h2$update,
progressfunction=function(down,up)
setTxtProgressBar(bar, down[2]))
h2$value() # return contents of page
The output is just a bunch of ====== across the console.

Answer 3

What about:
curlProgress=function(url, fname){
f = CFILE(fname, mode="wb")
prev=0
ret=curlPerform(url=url, writedata=f#ref, noprogress=FALSE,
progressfunction=function(a,b){
x=round(100*as.numeric(a[2])/as.numeric(a[1]))
if(!is.nan(x) && x!=prev &&round(x/10)==x/10) prev<<-x else x='.'
cat(x)
}, followlocation=T)
close(f)
cat(' Download', names(ret), '- Ret', ret, '\n')
}
?
It prints dots or percent download divisible by 10 and breaks line on 50%.
And with a small 223 KB file:
curlProgress("http://www.nirsoft.net/utils/websitesniffer-x64.zip", "test.zip")
it sounds like this:
................10...............20................30...............40...............50
..............................70...............80...............90...............100... Download OK - Ret 0
I start doubting that with standard R commands it is possible to reprint overwriting the current line, which is what RCurl does in non-GUI mode.