[R] help with restart

Wincent ronggui.huang at gmail.com
Wed May 5 10:34:30 CEST 2010

Dear all, I want to download webpage from a large number of webpage.
For example,

link <- c("http://gzbbs.soufun.com/board/2811006802/",
#  the actual vector will be much longer.

ans <- vector("list",length(link))

for (i in seq_along(link)){
  ans[[i]] <- readLines(url(link[i]))

The problem is, the sever will not response if the retrieval happens
too often and I don't know what the optimal time span between two
When the sever does not response to readLines, it will return an error
and stop. What I want to do is: when an error occurs, I put R to sleep
for say 60 seconds, and redo the readLines on the same link.

I did some search and guess withCallingHandlers and withRestarts will
do the trick. Yet, I didn't find much example on the usage of them.
Can you give me some suggestions? Thanks.

Wincent Rong-gui HUANG
Doctoral Candidate
Dept of Public and Social Administration
City University of Hong Kong

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