Using "At" to schedule Linux jobs, thanks to: Job scheduling with cron and at

There is lots out there about cron, but I like this explanation of "at", and sometimes it's what you need (esp. if your cron is temporarily hosed):

Listing 5. Using the at command

[ian@lyrebird ~]$ at -f mycrontest.sh -v 10:25 Sat Jul 7 10:25:00 2007 job 5 at Sat Jul 7 10:25:00 2007

Listing 6. Job output from at

From ian@lyrebird.raleigh.ibm.com Sat Jul 7 10:25:00 2007 Date: Sat, 7 Jul 2007 10:25:00 -0400 From: Ian Shields Subject: Output from your job 5 To: ian@lyrebird.raleigh.ibm.com It is now 10:25:00 on Saturday

Time specifications can be quite complex. Listing 7 shows a few examples. See the man page for at or the file /usr/share/doc/at/timespec or a file such as /usr/share/doc/at-3.1.10/timespec, where 3.1.10 in this example is the version of theat package.

Listing 7. Time values with the at command

[ian@lyrebird ~]$ at -f mycrontest.sh 10pm tomorrow job 14 at Sun Jul 8 22:00:00 2007 [ian@lyrebird ~]$ at -f mycrontest.sh 2:00 tuesday job 15 at Tue Jul 10 02:00:00 2007 [ian@lyrebird ~]$ at -f mycrontest.sh 2:00 july 11 job 16 at Wed Jul 11 02:00:00 2007 [ian@lyrebird ~]$ at -f mycrontest.sh 2:00 next week job 17 at Sat Jul 14 02:00:00 2007

Being nice

The nice value for a job is a measure of how nice it is to other users. See our tutorial LPI exam 101 prep: GNU and UNIX commands for information on the niceand renice commands.

The at command also has a -q option. Increasing the queue increases the nice value for the job. There is also a batchcommand, which is similar to the at command except that jobs are run only when the system load is low enough. See the man pages for more details on these features.

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Listing 11. Displaying and removing jobs with atq and atrm

[ian@lyrebird ~]$ atq 16 Wed Jul 11 02:00:00 2007 a ian 17 Sat Jul 14 02:00:00 2007 a ian 14 Sun Jul 8 22:00:00 2007 a ian 15 Tue Jul 10 02:00:00 2007 a ian [ian@lyrebird ~]$ atrm 16 14 15 [ian@lyrebird ~]$ atq 17 Sat Jul 14 02:00:00 2007 a ian ...

Linux tip: Job scheduling with cron and at

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