With any POSIX-conforming shell, you can also use:
This works to guarantee that only one process holds the lock (assuming that lockfile is an absolute pathname), but the read could fail if the lock was held at the time you requested the lock but the lock holder terminated before the read was processed. (So, you need to verify that the read worked rather than assume that it will always succeed.)
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 CENTOS
dotlockfile
DOTLOCKFILE(1) Cistron Utilities DOTLOCKFILE(1)NAME
dotlockfile - Utility to manage lockfiles
SYNOPSIS
/usr/bin/dotlockfile [-p] [-c] [-m] [-l|-u|-t] [-r retries] [lockfile]
DESCRIPTION
Dotlockfile is a command line utility to safely create, test and remove lockfiles. Lockfiles are created in an NFS-safe way. Dotlockfile
can can also be used to lock and unlock mailboxes even if the mailspool directory is only writable by group mail.
The name dotlockfile comes from the way mailboxes are locked for updates on a lot of UNIX systems. A lockfile is created with the same
filename as the mailbox but with the string ".lock" appended.
The names dotlock and lockfile were already taken - hence the name dotlockfile :).
OPTIONS -l Create a lockfile. This is the default.
-u Remove a lockfile.
-c Check for the existence of a valid lockfile.
-t Touch an existing lockfile (update the timestamp).
-p Write the process-id of the calling process into the lockfile. Also when testing for an existing lockfile, check the contents for a
process-id to find out if the lockfile is still valid.
-r retries
The number of times dotlockfile retries to acquire the lock if it failed the first time before giving up. The initial sleep after
failing to acquire the lock is 5 seconds. After each next try, a sleep of 5 seconds extra occurs up to a maximum sleep of 60 seconds
between tries. The default number of retries is 5.
-m Lock or unlock the current users mailbox. The path to the mailbox is the default system mailspool directory (usually /var/mail) with
the username as gotten from getpwuid() appended. If the environment variable $MAIL is set, that is used instead. Then the string
".lock" is appended to get the name of the actual lockfile.
lockfile
The lockfile to be created/removed, unless the -m option is in effect.
RETURN VALUE
Zero on success, and non-zero on failure. For the -c option, sucess means that a valid lockfile is already present. When locking (the
default, or the -l option) dotlockfile returns the same values as the library function lockfile_create(3). Unlocking a non-existant lock-
file is not an error.
NOTES
The lockfile is created exactly as named on the command line. The extension .lock is not automatically added.
This utility is a lot like the lockfile(1) utility included with procmail, and the mutt_dotlock(1) utility included with mutt. However the
command-line arguments differ, and so does the return status. It is believed that dotlockfile is the most flexible implementation, since it
automatically detects when it needs to use priviliges to lock a mailbox, and does it safely.
The above mentioned lockfile_create(3) manpage is present in the liblockfile-dev package.
BUGS
None known.
SEE ALSO lockfile_create(3), maillock(3)AUTHOR
Miquel van Smoorenburg, miquels@cistron.nl
15 May 2003 DOTLOCKFILE(1)