topic Re: Comments in Crontab in Operating System - HP-UX

Comments in Crontab

Kim Doty — Mon, 29 Apr 2002 14:26:17 GMT

I have some cron jobs that we sometimes need to stop running for a few days. I can't find any docs on whether using a # will comment out the line or not, so I've been deleting the line altogether and then replacing it when we want the job again. Does a # in crontab comment out the line like in other unix scripts?

Re: Comments in Crontab

hpuxrox — Mon, 29 Apr 2002 14:29:12 GMT

One word,

YES

Re: Comments in Crontab

MANOJ SRIVASTAVA — Mon, 29 Apr 2002 14:31:28 GMT

Hi Kim

# will comment the command . It will read it as a comment line and not a command line.

Manoj Srivastava

Re: Comments in Crontab

John Carr_2 — Mon, 29 Apr 2002 14:31:46 GMT

Hi

HP do not support comments in the crontab file.

make a copy of the file then edit the original to remove the non required entries.

John.

Re: Comments in Crontab

John Carr_2 — Mon, 29 Apr 2002 14:33:04 GMT

Hi

and when you want to put the lines back simply copy the backed up file over the crontab file being used.

John.

Re: Comments in Crontab

Kim Doty — Mon, 29 Apr 2002 14:34:23 GMT

Ok, now I'm confused, 2 yeses and a no. I am running HP-UX 11.0 if that makes a difference.

Re: Comments in Crontab

Victor_5 — Mon, 29 Apr 2002 14:34:57 GMT

Yes, for sure.

Re: Comments in Crontab

hpuxrox — Mon, 29 Apr 2002 14:36:22 GMT

Kim,

YES!

I have been doing it for years.

Re: Comments in Crontab

Darrell Allen — Mon, 29 Apr 2002 14:39:30 GMT

Hi Kim,

man crontab says:

<>
Blank lines and those whose first non-blank character is # will be ignored.
<>

It works fine to use comments in your crontab. Blank lines also.

Darrell

Re: Comments in Crontab

MANOJ SRIVASTAVA — Mon, 29 Apr 2002 14:44:09 GMT

Hi Kim

Please donot be confused , all of us run this stuff . and it works , it is a standard ASCII file and if you see a template which looks like this

#ident "@(#)root 1.14 97/03/31 SMI" /* SVr4.0 1.1.3.1 */
#
# The root crontab should be used to perform accounting data collection.
#
# The rtc command is run to adjust the real time clock if and when
# daylight savings time changes.
#
10 3 * * 0,4 /etc/cron.d/logchecker
10 3 * * 0 /usr/lib/newsyslog
15 3 * * 0 /usr/lib/fs/nfs/nfsfind
1 2 * * * [ -x /usr/sbin/rtc ] && /usr/sbin/rtc -c > /dev/null 2>&1
01 0 * * 4 /root/backups/arbdat01_backup.sh
20 4 * * * . /etc/env.BDDM; /opt/BDDM/bin/traceCleanup > /dev/null 2>&1 #BDDM
05 3 * * * . /etc/env.BDDM; /opt/BDDM/bin/DMbackup > /dev/null 2>&1 #BDDM
35 0,12 * * * . /etc/env.BDDM; /opt/BDDM/bin/logchecker > /dev/null 2>&1 #BDDM

at the start you will see lines which are commented , that doesnot mena that the same are ecuted.

All the best.

Manoj Srivastava

Re: Comments in Crontab

John Carr_2 — Mon, 29 Apr 2002 14:44:38 GMT

Hi Kim sorry to have confused you

I should have said YES because it does work but I have been led to believe by HP that the supported method to do as you wish is using several crontab files rather than comments to stop jobs running.

so YES it does work and its not supported

cheers
John

Re: Comments in Crontab

Jeff Schussele — Mon, 29 Apr 2002 14:52:22 GMT

Hi Kim,

One thing to keep in mind is that the crontab file(s) are only read when cron starts up.

So you should edit with the crontab -e command, crontab ~/your_cron_file OR edit the file manually and kill -HUP the cron PID. All methods will "force" a reread of the crontab files.

Rgds,
Jeff

Re: Comments in Crontab

hpuxrox — Mon, 29 Apr 2002 14:57:17 GMT

Jeff Schussele,

SIGHUP cron? I have never had to do that in the past.

just crontab -e

Works for me everytime.

-Yates

Re: Comments in Crontab

Jeff Schussele — Mon, 29 Apr 2002 15:06:53 GMT

Hi Yates,

If one *manually* edits w/o using crontab -e , for example using vi, then one would have to kill -HUP the cron PID.
I agree that crontab -e is the easiest....but you also run the risk of saving a corrupt/typo'd file inadvertently.
The recommended method is to create the file in one's home dir & use the crontab ~/my_cron_file command to let it place it & restart the cron daemon. This also gives one the opportunity to have *several* cron files - precisely what this user is looking for.
But I also use crontab -e frequently.......

Rgds,
Jeff

Re: Comments in Crontab

hpuxrox — Mon, 29 Apr 2002 15:15:18 GMT

Jeff Schussele,

You are correct, for the method you stated.

I hope I didn't sound to defensive.

Peace,

Re: Comments in Crontab

Jeff Schussele — Mon, 29 Apr 2002 15:19:08 GMT

Hi Yates,

No...not at all.
No offense taken, nor proffered

Have a great day,
Jeff

Re: Comments in Crontab

Richard Darling — Tue, 30 Apr 2002 11:40:28 GMT

Hi Kim,
Don't know if you are convinced yet, but everytime that we have a holiday I suspend my backups using crontab -e and comment out the backup command with a # sign. I then remove the # sign with crontab -e when I want the backup to be reactivated.
I have never had a problem.
RD

Re: Comments in Crontab

Emanuel Sardenberg — Tue, 30 Apr 2002 18:35:54 GMT

Hi!

Cronfile Example

####
0 8 * * 1,2,4,5 /lnULOGGLOBO.sh 2>&1
0 10 * * 0,3,6 /lnULOGGLOBO.sh 2>&1
#15 * * * * /moncpu.sh > /moncpu.log 2>&1
####

Re: Comments in Crontab

Jack Werner — Tue, 30 Apr 2002 20:09:01 GMT

Hi there,
Here's a little something an
admin should kep in mind, esp if you are changing crontabs for users other than root. If you edit the crontab directly, vi /usr/spool/cron/crontabs/<> then you must recycle the cron daemon for it to "see" the modified crontab. Most systems /etc/inittab launch cron with the "respawn" option, so it is OK to kill the cron pid.

Re: Comments in Crontab

Bill Hassell — Tue, 30 Apr 2002 22:20:48 GMT

Just to clarify: HP supports the behavior described in the man page, that is, a comment is defined is a blank line or where the first non-blank character is #, just like a shell. Sorry that someone from HP said it wasn't 'supported'. Perhaps they meant 'recommended', but even then, I would disagree.

cron simply doesn't care what you put in your crontab file as comments. As far as managing crontab files, there are as many methids as there are sysadmins. My method is to always keep root's 'official' crontab file in root's $HOME, specifically in the .cronfiles directory. That way, if a newbie sysadmin blows away the crontab entry, it can easily be restored. You make the changes to the $HOME/.cronfiles/crontab.root file, then simply replace the current crontab entry with:

crontab $HOME/.cronfiles/crontab.root

No restart of cron, no crontab -e, etc. I find that with multiple root admins, this works the best. And the .cronfiles directory keeps the crontab reference a bit hidden.