One Implementation...
Sorry to chime in so late, but I haven't been monitoring this forum as closely as I used to (an RSS feed would remedy that :-)
Just a couple of notes ...
* I stole the daemon code from WeBrick. I could have just used WeBricks version directly, but I figured folk would like to see the implementation.
* I added pid file support in addition to the "abort file"
* It's all very unix-y. Pieces will probably work under windows, but it is untested on that platform.
* I seriously considered naming the NonDaemon class "Aengel", but figured that bad puns imbeded into code is not a good idea.
* I use the file modified time to detect file changes (don't know what you had in mind).
* As I'm posting here, I see I missed the non-zero length test. I'll leave that as an exercise for the student (I love saying that).
The code has been manually tested on Linux and works well there. It could probably use a cleanup refactoring and a light sprinkling of comments. Feedback is welcome.
#!/usr/bin/env ruby\n\nrequire 'optparse'\nrequire 'fileutils'\n\n# Daemon borrowed from WeBrick :-)\nclass Daemon\n def Daemon.start\n exit!(0) if fork\n Process::setsid\n exit!(0) if fork\n Dir::chdir("/")\n File::umask(0)\n [ STDIN, STDOUT, STDERR ].each{|io|\n io.reopen("/dev/null", "r+")\n }\n yield if block_given?\n end\nend\n\nclass NonDaemon\n def NonDaemon.start\n yield if block_given?\n end\nend\n\n# Add an alive? method to the Process module\nmodule Process\n unless defined?(alive?)\n def Process.alive?(pid)\n Process.kill 0, pid rescue nil\n end\n end\nend\n\nclass Sweeper\n class SweepError < StandardError; end\n class ConfigError < SweepError; end\n class AlreadyRunningError < SweepError; end\n \n def initialize(opts)\n @source = opts[:source]\n @dest = opts[:dest]\n @command = opts[:command]\n @stdout = opts[:out]\n @stderr = opts[:err]\n @sleep = opts[:sleep] || 10\n @abort_file = opts[:abort]\n @pid_file = opts[:pid]\n @do_stamps = opts[:time_stamp]\n @filestamps = {}\n @runner = opts[:daemon] ? Daemon : NonDaemon\n @halt_requested = false\n need @source, "Source directory"\n need @dest, "Destination directory"\n need @command, "Command"\n @source = File.expand_path(@source)\n @dest = File.expand_path(@dest)\n @stdout = File.expand_path(@stdout) if @stdout\n @stderr = File.expand_path(@stderr) if @stderr\n end\n\n def need(value, msg)\n fail ConfigError, "Error: #{msg} not specified" if value.nil?\n end\n\n def timestamp(time)\n time.strftime("%Y%m%d-%H%M%S")\n end\n\n def log(msg)\n puts "#{timestamp(Time.new)}: #{msg}"\n end\n\n def redirect_io\n STDOUT.reopen(@stdout, "w") if @stdout\n STDERR.reopen(@stderr, "w") if @stderr\n end\n\n def done?\n return true if @halt_requested\n if @abort_file && File.exists?(@abort_file)\n FileUtils.rm @abort_file\n return true\n end\n false\n end\n\n def process_file(fn, stamp)\n destfn = File.basename(fn)\n destfn = "#{destfn}-#{timestamp(stamp)}" if @do_stamps\n destpath = File.join(@dest, destfn)\n FileUtils.mv fn, destpath\n cmd = %{#{@command} #{destpath} &}\n log "RUNNING [#{cmd}]"\n system cmd\n end\n\n def check_files\n newstamps = Dir["#{@source}/*"].inject({}) { |h, fn|\n h[fn] = File.stat(fn).mtime\n h\n }\n newstamps.each do |fn, time_stamp|\n if @filestamps[fn].nil?\n\tlog "NEW [#{fn}]"\n elsif @filestamps[fn] == time_stamp\n\tlog "STABLE [#{fn}]"\n\tprocess_file(fn, newstamps[fn])\n end\n end\n @filestamps = newstamps\n STDOUT.flush\n end\n \n def write_pid\n return if @pid_file.nil?\n open(@pid_file, "w") do |f| f.puts Process.pid end\n end\n\n def sweep_loop\n redirect_io\n write_pid\n log "STARTING SWEEP"\n loop do\n break if done?\n check_files\n sleep(@sleep)\n end\n log "EXITING SWEEP"\n end\n\n def check_already_running\n return false if @pid_file.nil?\n pid = open(@pid_file) { |f| f.gets.to_i } rescue nil\n if pid && Process.alive?(pid)\n fail AlreadyRunningError, "Sweep is already running (pid #{pid})"\n end\n end\n\n def halt\n @halt_requested = true\n log "HALT REQUESTED"\n end\n\n def run\n check_already_running\n @runner.start do sweep_loop end\n end\nend\n\ndef sweep_main\n options = { }\n ARGV.options do |opts|\n opts.on("-a", "--abort_file=file", "Abort File" ) do |value|\n options[:abort] = value\n end\n opts.on("-c", "--command=cmd", "Command to run" ) do |value|\n options[:command] = value\n end\n opts.on("-D", "--dest=dir", "Destination directory") do |value|\n options[:dest] = value\n end\n opts.on("-d", "--daemon", "Run as a daemon") do |value|\n options[:daemon] = value \n end\n opts.on("-e", "--stderr=file", "Standard error") do |value|\n options[:err] = value\n end\n opts.on("-h", "--help", "Show this help message.") do\n puts opts\n exit\n end\n opts.on("-k", "--kill", "Kill the currently running sweep process") do | value|\n options[:kill] = value\n end\n opts.on("-l", "--log_file", "Log file") do |value|\n options[:log] = value\n end\n opts.on("-o", "--stdout=file", "Standard output") do |value|\n options[:out] = value \n end\n opts.on("-p", "--pid=file", "PID file") do |value|\n options[:pid] = value\n end\n opts.on("-S", "--source=dir", "Source directory") do |value|\n options[:source] = value\n end\n opts.on("-s", "--sleep=n", Integer, "Sleep Time") do |value|\n options[:sleep] = value\n end\n opts.on("-t", "--time_stamp", "Include time stamp") do |value|\n options[:time_stamp] = value\n end\n opts.on("-v", "--verbose", "Verbose mode") do |value|\n options[:verbose] = value\n end\n \n opts.parse!\n end\n\n if options[:verbose]\n puts "Options are:"\n options.each do |key, value|\n puts " #{key}: #{value}"\n end\n end\n\n if options[:kill]\n if options[:pid].nil?\n fail Sweeper::ConfigError, "Option --kill requires --pid"\n end\n unless File.exists? options[:pid]\n fail Sweeper::ConfigError, "No pid file found"\n end\n pid = open(options[:pid]) { |f| f.gets.to_i }\n puts "Sending signal to pid #{pid}"\n Process.kill "INT", pid\n else\n sweeper = Sweeper.new(options)\n trap("INT") { sweeper.halt }\n sweeper.run\n end\n\nrescue Sweeper::SweepError => ex\n puts "Error: #{ex.message}"\nend\n\nif __FILE__ == $0 then\n sweep_main\nend\n
