From: Han Holl <han.holl@...>
Date: 2005-02-16T23:48:09+09:00
Subject: flock doesn't work with exec'd files ?

Hello,

The following doesn't work as I expected and would like <g>:

#!/usr/bin/ruby

if 'exec' == ARGV[0]
  File.new($0).flock(File::LOCK_EX)
  puts "Locked #{$0} at #{Time.now}"
  exec($0, 'sleep')
elsif 'sleep' == ARGV[0]
  sleep(10)
  File.new($0).flock(File::LOCK_UN)
  puts "Unlocked #{$0} at #{Time.now}"
  sleep(10)
  exit
else
  File.new($0).flock(File::LOCK_SH )
  puts "Got shared lock at #{Time.now}"
end
# end-of-program

If I call this /tmp/trylock.rb, and chmod a+x it,  and I type in:

/tmp/trylock.rb exec &
/tmp/trylock.rb

I get something like:
Locked /tmp/trylock.rb at Wed Feb 16 14:26:49 CET 2005
Unlocked /tmp/trylock.rb at Wed Feb 16 14:26:59 CET 2005
Got shared lock at Wed Feb 16 14:27:09 CET 2005

Strace shows that no system-call to flock(n, LOCK_UN) is ever made.
Is there something I missed here ?

Thanks in advance for any hints,

Cheers,

Han Holl