I have a process which can run one instance at a time. Currently we have multiple scripts trying to kickoff this process. I wanted to implement the semaphore mechanism to achieve this.
I was going through few examples. The below code seems to be reasonable solution.
But I am concerned about limitations, eg. we do not have much control on the filename (in the above case, "important")
Especially our team who maintains the application in Production are not experts.
Which technique (command) would you recommend (least errors and less experience to maintain)
Hi,
I have written below check lockfile script but need some tweaking on it.
If there is a lockfile from present, I need the script to retry every 10 seconds to see if the lockfile is still there. After 120 seconds it should send an email.
In my current version, if the script encounters... (6 Replies)
Just tried out the following code from "Using lockfiles in shell scripts":
#!/bin/bash
if ; then
echo "File exists"
else
echo "File does not exists. Create file now."
echo 1 > number.txt
fi
lockfile script.lock
a=$(/usr/bin/tail -n 1 number.txt)
if ; then... (1 Reply)
Hi all,
I have to test some user priviliges. The goal is to be sure that an unauthorized user can't restart some modules (ssh, mysql etc...).
I'm trying to automate it with a shell script but in same cases I got the syslog broadcast message.
Is there any way to simply get a return code... (3 Replies)
Hi,
I am new to this forum, could any one please help me to understand the LOCKFILE command with an example and what exactly it is used for and how it is used.
Thanks
Reshu289 (4 Replies)
Hello,
I have been working on using "flock"/file lock to prevent two instances of a bash script from being executed. Below is a simplified version of what I have to illustrate the flock part. It works as it is set up there below however the piece I am trying to figure out is how to get it to... (2 Replies)
I'm changing my mindset from a few big processes moving data from a few sources under an external, dependency-based scheduler to multiple processes moving data from many sources run by each client cron and possibly interfering with each other. It has the benefits of more granular code but I'm... (11 Replies)
Hi i have a script that check pings and i use flock to so the script wont run
multipul times :
its not the whole script but this is the idea :
(
flock -x -w 3 200 || exit 1
/usr/sbin/fping -c$count -i$interval -a $hosts > $FILE1 2>&1
) 200>/var/lock/.myscript.exclusivelock
now i... (4 Replies)
Discussion started by: batchenr
4 Replies
LEARN ABOUT DEBIAN
paranoid::lockfile
Paranoid::Lockfile(3pm) User Contributed Perl Documentation Paranoid::Lockfile(3pm)NAME
Paranoid::Lockfile - Paranoid Lockfile support
VERSION
$Id: Lockfile.pm,v 0.65 2011/12/08 07:53:07 acorliss Exp $
SYNOPSIS
use Paranoid::Lockfile;
$rv = plock($lockfile);
$rv = punlock($lockfile);
$rv = pcloseLockfile($lockfile);
DESCRIPTION
This modules provides a relatively safe locking mechanism across multiple processes. This does not work over NFS or across remote systems,
this is only intended for use on a single system at a time, and only on those that support flock.
sysopen is used to avoid race conditions with multiple process attempting to create the same file simultaneously.
SUBROUTINES /METHODS
plock
$rv = plock($filename);
This function attempts to safely create or open the lockfile. It uses sysopen with O_CREAT | O_EXCL to avoid race conditions with other
processes. Returns a true if successful.
Your can pass an optional second argument which would be a string of either 'write' or 'shared'. The default is 'write', which locks the
file in exclusive write mode.
You can pass an optional third argument which would be the lockfile filesystem permissions if the file is created. The default is 0600.
NOTE: This function will block until the advisory lock is granted.
punlock
$rv = punlock($filename);
This function removes any existing locks on the specified filename using flock. If no previous lock existed or it was successful it
returns true. This does not, however, close the open filehandle to the lockfile.
pcloseLockfile
$rv = pcloseLockfile($filename);
This function releases any existing locks and closes the open filehandle to the lockfile. Returns true if the file isn't currently open or
the operation succeeds.
DEPENDENCIES
o Fcntl
o Paranoid
o Paranoid::Debug
BUGS AND LIMITATIONS AUTHOR
Arthur Corliss (corliss@digitalmages.com)
LICENSE AND COPYRIGHT
This software is licensed under the same terms as Perl, itself. Please see http://dev.perl.org/licenses/ for more information.
(c) 2005, Arthur Corliss (corliss@digitalmages.com)
perl v5.14.2 2011-12-08 Paranoid::Lockfile(3pm)