test/flock.py

   1 """
   2 flock.py -- Simple exclusive lock fcntl test program in Python.
   3
   4 Usage: python /path/to/lock_test.py
   5
   6 The script will try to open(create if needed), then lock a 'lock_test.txt'
   7 file in the current working directory, write its PID in it, then wait for
   8 the user to press enter, then release the lock, close the file and exit.
   9
  10 Tested on both stock Python 2.3.5 and Python 2.4.2
  11 """
  12 from sys import stdout, exc_info
  13 from traceback import print_exception
  14 from os import getcwd, getpid
  15 from os.path import join
  16 from fcntl import lockf, LOCK_UN, LOCK_EX
  17
  18 try:
  19     filename = join(getcwd(),'lock_test.txt')
  20     print 'Opening or creating "%s"...' % filename,
  21     f = file(filename,'a')
  22     print 'ok'
  23     print 'Acquiring lock...',
  24     stdout.flush()
  25     lockf(f,LOCK_EX)
  26     print 'ok'
  27     print 'Writing pid (%d)...' % getpid(),
  28     print >> f, "PID:",  getpid()
  29     print 'ok'
  30     raw_input('[Press enter to exit]')
  31     print 'Releasing lock...',
  32     lockf(f,LOCK_UN)
  33     print 'ok'
  34     print 'Closing file...',
  35     f.close()
  36     print 'ok'
  37 except:
  38     print 'failed'
  39     print '='*80
  40     print_exception(*exc_info())
  41     print '='*80