[R] proxy setting RedHat Linux

[Jonathan Q. Li]

Hi,

I was trying to update packages with my R 1.6 under RedHat 8.0 system.
When entering this command,
 > update.packages()

It simply says,
    trying URL `http://cran.r-project.org/src/contrib/PACKAGES'

But nothing happens.

Is this a problem with my proxy setting since I am working behind a 
firewall? It seems so:

 > Sys.getenv("http_proxy")
http_proxy
        ""

Then the documentation in "download.file" says that Sys.putenv won't 
work in setting the proxy. It says " These environment variables must be 
set before the download code
     is first used: they cannot be altered later by calling
     `Sys.putenv'.".

I don't understand what this means: "set it before the download code is 
first used". I have installed the R 1.6 simply from  RPM in CRAN.

Thanks in advance for your help.
Jonathan