R help - Aug 2012 - Loop for readLines(URL[i]) fails when URL returns Error 404

I have a loop over readLines(URL[i]) which works fine until it hits a bad URL
(e.g., a
URL that returns a 404 Error).

How can I handle this with a test for this error condition.

I read the tryCatch( ? ) description but can't figure out how to apply it
here. Perhaps
there is something else that would work better.

Hello,

For example:

url <- c("http://www.example.com",
"http://www.example5.com")
res <- vector("list", length(url))
for (i in 1:length(url)) res[[i]] <- try(readLines(url[i]), silent = TRUE)
res[[2]]
## [1] "Error in file(con, \"r\") : cannot open the
connection\n"
## attr(,"class")
## [1] "try-error"
## attr(,"condition")
## <simpleError in file(con, "r"): cannot open the connection>

# or
for (i in 1:length(url)) res[[i]] <- tryCatch(readLines(url[i]), error =
function (e) conditionMessage(e))
res[[2]]
## [1] "cannot open the connection"

-- 
Noia Raindrops
noia.raindrops at gmail.com