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Sourcecode: backintime version File versions

guiapplicationinstance.py

#    Back In Time
#    Copyright (C) 2008-2009 Oprea Dan
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with this program; if not, write to the Free Software Foundation, Inc.,
#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


import os
import os.path
import time


#class used to handle one application instance mechanism
class GUIApplicationInstance:

      #specify the base for control files
      def __init__( self, base_control_file, raise_cmd = '' ):
            self.pid_file = base_control_file + '.pid'
            self.raise_file = base_control_file + '.raise'
            self.raise_cmd = raise_cmd

            #remove raise_file is already exists
            try:
                  os.remove( self.raise_file )
            except:
                  pass

            self.check( raise_cmd )
            self.start_application()

      #check if the current application is already running
      def check( self, raise_cmd ):
            #check if the pidfile exists
            if not os.path.isfile( self.pid_file ):
                  return

            #read the pid from the file
            pid = 0
            try:
                  file = open( self.pid_file, 'rt' )
                  data = file.read()
                  file.close()
                  pid = int( data )
            except:
                  pass

            #check if the process with specified by pid exists
            if 0 == pid:
                  return

            try:
                  os.kill( pid, 0 ) #this will raise an exception if the pid is not valid
            except:
                  return

            #exit the application
            print "The application is already running ! (pid: %s)" % pid

            #notify raise
            try:
                  file = open( self.raise_file, 'wt' )
                  file.write( raise_cmd )
                  file.close()
            except:
                  pass

            exit(0) #exit raise an exception so don't put it in a try/except block

      #called when the single instance starts to save it's pid
      def start_application( self ):
            file = open( self.pid_file, 'wt' )
            file.write( str( os.getpid() ) )
            file.close()

      #called when the single instance exit ( remove pid file )
      def exit_application( self ):
            try:
                  os.remove( self.pid_file )
            except:
                  pass

      #check if the application must to be raised
      #return None if no raise needed, or a string command to raise
      def raise_command( self ):
            ret_val = None

            try:
                  if os.path.isfile( self.raise_file ):
                        file = open( self.raise_file, 'rt' )
                        ret_val = file.read()
                        file.close()
                        os.remove( self.raise_file )
            except:
                  pass

            return ret_val


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