Catch errors and warnings from log file

warningerrorlog.R

# Load the 2 functions below,
# then test errors with:
# downloadfile1(url="xxxx", destfile="/tmp/xxxx", logfile="~/rlog.txt")
# ~/rlog.txt contains 
#     Error in download.file(url = url, destfile = destfile, ...): cannot download all files
# 
# then
#
# downloadfile2(url="xxxx", destfile="/tmp/xxxx", logfile="~/rlog.txt")
# ~/rlog.txt contains the warning message
#     simpleWarning in download.file(url = url, destfile = destfile, ...): URL 'HTTP://xxxx/': status was 'Couldn't resolve host name'
# but it doesn't contain the error message, how to capture both error and warning?


#' Download a file, catch errors only
#' @param url an url
#' @param destfile, destination file
#' @param logfile, log file
#' @param ... other parameters passed to \link{download.file}
downloadfile1 <- function(url, destfile, logfile, ...){
    downloadstatus <- 1
    tryCatch({
        # Store the download status returned by download.file
        downloadstatus <- download.file(url = url, destfile = destfile, ...)

    }, error = function(errorcondition){
        # Add error message to the log file
        write(toString(errorcondition), logfile, append=TRUE)
    }
    )
    # Returns the download status
    invisible(downloadstatus)
}



#' Download a file, catch errors and warnings
downloadfile2 <- function(url, destfile, logfile, ...){
    downloadstatus <- 1
    tryCatch({
        # Store the download status returned by download.file
        downloadstatus <- download.file(url = url, destfile = destfile, ...)

    }, error = function(errorcondition){
        # Add error message to the log file
        write(toString(errorcondition), logfile, append=TRUE)
    }, warning = function(warningcondition){
        # Add warning message to the log file
        write(toString(warningcondition), logfile, append=TRUE)
    }
    )
    # Returns the download status
    invisible(downloadstatus)
}