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rubyloggingtailputs

Ruby logging in realtime

I am trying to log some output to a file in realtime using Ruby. I would like to be able to do a tail -f on the log file and watch the output get written. At the moment the file only gets written to once I stop the ruby script. What I am trying to do seems straight forward.

I create the logfile

log = File.open(logFileName, "a")

I later write to it using:

log.puts "#{variable}"

Again, the log file gets created and the correct entries are in it but only once I have stopped the script from running. I need to tail the log file and see in realtime.

Thanks in advance!

Solution

  • Normally file input and output is buffered to a degree. You can disable this behaviour by flipping a flag:

    log.sync = true

    This disables buffering by forcing a flush operation after each write. With that enabled, programs like tail -f can read the data in real-time.