sample-log4r.R

# Package for Log4R
library("log4r")

# Default Logger
default_logger <- logger()

# Debug level enabled Logger (by default DEBUG level is suppressed)
debug_logger <- logger("DEBUG")

# File Logger
log_file <- "sample.log"
file_logger <- logger("WARN", appenders = file_appender(log_file))

# Sample program
urls <- c(
    "http://stat.ethz.ch/R-manual/R-devel/library/base/html/connections.html",
    "http://en.wikipedia.org/wiki/Xz",
    "yyyyy"
)
readUrl <- function(url) {
    out <- tryCatch(
        {
            debug(debug_logger, "This is the 'try' part")

            readLines(con=url, warn=FALSE) 
        },
        error=function(cond) {
            error(file_logger, paste("URL does not seem to exist:", url))
            error(file_logger, "Here's the original error message:")
            error(file_logger, cond)

            return(NA)
        },
        warning=function(cond) {
            warn(file_logger, paste("URL caused a warning:", url))
            warn(file_logger, paste("Here's the original warning message:"))
            warn(file_logger, cond)

            return(NULL)
        },
        finally={
            info(default_logger, paste("Processed URL:", url))
            info(default_logger, "Some other message at the end")
        }
    )    

    return(out)
}

for (url in urls) {
    readUrl(url)
}