[root@trixbox127772 ~]# crontab -l

# Update time daily
0 2 * * * /usr/sbin/ntpdate tick.ucla.edu > /dev/null 2>&1

# Ping systems every 15 mins
*/15 * * * * /bin/nice /usr/bin/perl /var/adm/bin/ping_main.pl -randsleep

# Rotate asterisk logs daily
0 0 * * * /usr/sbin/asterisk -r -x 'logger rotate'

# Generate 5-min charts
*/5 * * * * /bin/nice -n 19 /usr/bin/perl /var/adm/bin/rrd_graph.pl
0 0 * * * /var/adm/bin/validation_check.pl &> /dev/null 2>&1
24 5 * * * perl /var/adm/bin/registry.pl &> /dev/null

30 * * * * /bin/nice -n 5 /etc/init.d/FONmon start >> /dev/null 2>> /dev/null

30 * * * * /bin/nice -n 7 /var/adm/bin/sync_linked_greet.pl >> /dev/null 2>> /dev/null
9 4 * * * /etc/webmin/cron/tempdelete.pl

1 * * * * if [ -n "$(/bin/grep Spitfire /etc/asterisk/sip.conf)" ]; then /usr/bin/perl -i.bak -pe 's/Brent Silversmith <235>//g' /etc/asterisk/sip.conf; asterisk -rx 'sip reload'; echo "[$(date)] cronjob: Removed Spitfire from callerid field in sip.conf." >> /var/log/asterisk/messages; fi



That is the result of crontab -l

The last cron tab is not working.. I cant even see any evidence of it trying to run. Can someone help me with trying to get this thing working? And I want this to run every 30 seconds

This would run at 1 minute past the hour every hour ( although sometimes it needs to be 01, for example ). Perhaps it was meant to be */1 * * * * ?

I think the best granularity for cron is every minute. I am not aware of anything less.

Looks like a potential job for configuration management like puppet, cfengine etc. but, again, 30s response time is not going to be practical, AFAIK.

Maybe there's a solution to be had with inotify[1] (to check for modifications to sip.conf) so that you only execute your script when a change to the file occurs.

[1] if your system/kernel supports it.
https://github.com/rvoicilas/inotify-tools/wiki/
http://linux.die.net/man/1/inotifywatch

After updating it to run once a minute I am still not seeing any evidence of it running

Try creating a new file containing those shell commands and add the script name to the crontab instead. It's going to be more reliable and probably easier to debug.

1 members found this post helpful.

A big "I second that" to placing the commands in a script.
Use the #! line to specify what shell you want it to run under, otherwise it runs in the POSIX mode of the shell presented as /bin/sh.

cron does a great job of scheduling scripts and programs, not so well at acting as a shell or command processor.

1. do put that lot in a script eg do it all in Perl instead of calling different external cmds.
2. make the new Perl script a daemon and just have it wait 30s at the bottom of the main loop.

I'd also point out that although you can specify crontab jobs start time to the nearest minute, this entails creating a new process env every call/job and old jobs may overlap with new ones if they don't complete fast enough.
Just put a watchdog process in cron if you are paranoid, set to check every eg 5 mins to see if the daemon is running and restart it if not.