Hi guys,
I’m looking for a single line that essentially deletes the lockfile
argument passed to the unlock method, or deletes the instance variable
(default) lockfile. Like this, but simpler:
@lockfile = some_other_lockfile
def self.unlock(lockfile)
if File.exist?(lockfile)
File.delete(lockfile)
else
File.delete(@lockfile)
end
end
I was thinking of something along the following:
@lockfile = some_other_lockfile
def self.unlock
File.delete(lockfile) || File.delete(@lockfile)
end
…however, the File.delete method doesn’t return a true/false value
based on its success.
Any tips? Thanks in advance!
-David
David S. wrote:
File.delete(lockfile)
def self.unlock
File.delete(lockfile) || File.delete(@lockfile)
end
…however, the File.delete method doesn’t return a true/false value
based on its success.
Any tips? Thanks in advance!
-David
Use exceptions?
begin
File.delete(lf)
rescue Errno::ENOENT
File.delete(@lf)
end
Use exceptions?
begin
File.delete(lf)
rescue Errno::ENOENT
File.delete(@lf)
end
Thanks Joel. Forgive me, I’m just learning Ruby/scripting/programming. I
believe I understand your example, but (as far as I can tell) it doesn’t
really accomplish my goal, and seems to have the same functionality of
my first (longer) example.
Please let me know if I’ve missed something. 
In any case, I think I found a (seemingly) obvious solution to my
question:
@lockfile = some_other_lockfile
def self.unlock(lockfile)
File.exist?(lockfile) ? File.delete(lockfile) : File.delete(@lockfile)
end
Thanks again!
-David
File.delete(File.exists?(lockfile) ? lockfile : @lockfile)
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On 04/02/2009, at 5:07 AM, Joel VanderWerf [email protected]
2009/2/4 Julian L. [email protected]:
File.delete(File.exists?(lockfile) ? lockfile : @lockfile)
[lockfile, @lockfile].any? {|f| File.delete(f) rescue false}
Cheers
robert
David S. wrote:
really accomplish my goal, and seems to have the same functionality of
File.exist?(lockfile) ? File.delete(lockfile) : File.delete(@lockfile)
end
With exceptions, you are saying “try to delete lf; if that fails
(because the file doesn’t exist) then try to delete @lf”. Other failures
(e.g., lf permissions are wrong, or @lf doesn’t exist) are reported
normally as exceptions.
One advantage to doing it this way is that the delete is an atomic
operation. With
File.exist?(lockfile) ? File.delete(lockfile) :
File.delete(@lockfile)
there is the possiblity that #exist? will return true, but in the brief
time before #delete is called, some other process deletes the file.
Btw, it looks to me like your #unlock implementation above is the same
as your first implementation. The ? : construct is really the same as
if…else, just more compact.
Robert K. wrote:
2009/2/4 Julian L. [email protected]:
File.delete(File.exists?(lockfile) ? lockfile : @lockfile)
[lockfile, @lockfile].any? {|f| File.delete(f) rescue false}
If #delete fails on lockfile for some reason other than ENOENT, this
code will try to delete @lockfile.
On 05.02.2009 18:49, Joel VanderWerf wrote:
Robert K. wrote:
2009/2/4 Julian L. [email protected]:
File.delete(File.exists?(lockfile) ? lockfile : @lockfile)
[lockfile, @lockfile].any? {|f| File.delete(f) rescue false}
If #delete fails on lockfile for some reason other than ENOENT, this
code will try to delete @lockfile.
This is correct. I thought that was intended. Didn’t you suggest
exactly this in your previous posting (atomic deletion)? Looking at the
original question it is not clear in which cases @lockfile should be
deleted - unless you take the code as spec.
Thanks for pointing this out!
Cheers
robert
Robert K. wrote:
exactly this in your previous posting (atomic deletion)? Looking at the
original question it is not clear in which cases @lockfile should be
deleted - unless you take the code as spec.
Thanks for pointing this out!
The only difference in my suggestion was to “Rescue Errno::ENOENT”,
which seems closer to the original intent of using #exists?..
begin
File.delete(lf)
rescue Errno::ENOENT
File.delete(@lf)
end