[R] R and HTTP get 'has file changed'

Dirk Eddelbuettel edd at debian.org
Fri Jul 13 04:25:15 CEST 2007

Is there a way, maybe using Duncan TL's RCurl, to efficiently test whether
an URL such as 


has changed?  I.e. one way is via a test of a page in that directory as per
(sorry about the long line, and this would be on Linux with links and awk

   > strptime(system("links -width 160 -dump http://cran.r-project.org/src/contrib/ | awk '/PACKAGES.html/ {print $3,$4}\'", intern=TRUE), "%d-%b-%Y %H:%M")
   [1] "2007-07-12 18:16:00"

and one can then compare the POSIXt with a cached value --- but requesting
the header would presumably be more efficient.

Is there are way to request the 'has changed' part of the http 1.1 spe
directly in R?

Thanks, Dirk

Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison

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