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Perl Programming Language
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Need suggestions on a good locking module
I have a script that I want to run, but only one instance. So I want
to set up crontab to start it every minute, but if it is already
running, I would exit.
I looked at LockFile::Simple but I do not like it. I want to find a
module that opens a file with O_EXCL and uses that for locking. (local
hard drive filesystem only)
I know that I could just use sysopen, but I am hoping that perhaps a
well debugged module would clean some gotchas that I did not think
about.
thanks
i
On Jun 4, 8:33 am, Ignoramus27175 <ignoramus27...@NOSPAM.
27175.invalid> wrote: > I have a script that I want to run, but only one instance. So I want > to set up crontab to start it every minute, but if it is already > running, I would exit. > I looked at LockFile::Simple but I do not like it. I want to find a
> module that opens a file with O_EXCL and uses that for locking. (local
> hard drive filesystem only)
the end delete a file. If the file exists, then exit program.
HTH
Dinakar Desai
In article <MP6dndxNyasrifnbnZ2dnUVZ_v-tn@giganews.com>, ignoramus27@NOSPAM.27175.invalid says...
>I have a script that I want to run, but only one instance. So I want
>to set up crontab to start it every minute, but if it is already
>running, I would exit.
>I looked at LockFile::Simple but I do not like it. I want to find a
>module that opens a file with O_EXCL and uses that for locking. (local
>hard drive filesystem only)
>I know that I could just use sysopen, but I am hoping that perhaps a
>well debugged module would clean some gotchas that I did not think
>about.
cheers
Heinrich
--
Heinrich Mislik
Zentraler Informatikdienst der Universitaet Wien
A-1010 Wien, Universitaetsstrasse 7
Tel.: (+43 1) 4277-14056, Fax: (+43 1) 4277-9140
On Jun 5, 4:23 am, Heinrich.Mis@univie.ac.at (Heinrich Mislik)
wrote:
> In article <MP6dndxNyasrifnbnZ2dnUVZ_v-tn @giganews.com>, ignoramus27 @NOSPAM.27175.invalid says... > >I have a script that I want to run, but only one instance. So I want
> >to set up crontab to start it every minute, but if it is already
> >running, I would exit.
> Look at Proc::PID::File
leads me to believe File::Pid is cleaner.
Looks like Proc::PID::File isnt portable (uses ps in backticks).
File::Pid uses perl's kill().
Anyone got any opinions on which is better?
Todd W.
des @gmail.com wrote: >At the start of the program create a file if it does not exist and at >the end delete a file. If the file exists, then exit program.
lockfile would never be deleted.
And you have a race condition, between testing if the file exists, and
actually creating it (unless you're openign the file with the O_EXCL
flag (from Fcntl), which somehow I doubt.) (see
http://bama.ua.edu/cgi-bin/man-cgi?open+2)
--
Bart.
On Tue, 05 Jun 2007 20:39:09 -0000, trwww <waveri @gmail.com> wrote: > On Jun 5, 4:23 am, Heinrich.Mis @univie.ac.at (Heinrich Mislik) > wrote: >> In article <MP6dndxNyasrifnbnZ2dnUVZ_v-tn @giganews.com>, ignoramus27 @NOSPAM.27175.invalid says... >> >I have a script that I want to run, but only one instance. So I want
>> >to set up crontab to start it every minute, but if it is already
>> >running, I would exit.
>> Look at Proc::PID::File
> Theres also File::Pid. A (very) quick glance at the source for both
> leads me to believe File::Pid is cleaner.
> Looks like Proc::PID::File isnt portable (uses ps in backticks).
> File::Pid uses perl's kill().
> Anyone got any opinions on which is better?
> Todd W.
called "lockfile" (I believe, part of procmail package) that does what
I want. So, my crontab entries look like this:
*/5 04-18 * * * if lockfile -r 1 /tmp/WatchDog.lock ; then $HOME/smile/support/WatchDog.pl; rm /tmp/WatchDog.lock ; fi > ~/log/watchdog.log 2>&1
This means that every 5 minutes I check the lock, and if it is
available, it gets locked and my process runs.
in /etc/rc.d/rc.local I remove these locks when I boot.
i
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