At

work in progress

Sissejuhatus

at	At, koondab sisestatud käsud ühte at-job-i, mis käivitatakse hiljem. At-job pärib oma keskkonna, st. käsu käivitatakse hetkel on töökataloog ja süsteemimuutujatd samasugused nagu oli sisestamisel At, erineb cron-ist. At on korraliseks kasutamiseks, cron on selleks kui mingit käsku vaja käivitada samal ajal perioodiliselt korduvalt.
atq	tavakasutaja korral loendab kasutaja ootel olevad tööd superuseri korral loendab kõikide kasutajate ootel olevad tööd
atrm	kustutab töid, mille töönumber on täpsustatud
batch	käivitab käsu kohe kui süsteemi load (koormatus) seda lubab, kui koormus langeb alla 0.8, või täpsustatud väärtuse atrun käsuga

Kasutamine ja näited

[1]

Töö käivitamine kindlaksmääratud kuupäeval ja ajal

root@server:~# at -v 23:55 16 dec Mon Dec 16 23:55:00 2013

warning: commands will be executed using /bin/sh at> rm *.txt at> uptime>>uptime.at.txt at> ps -axu>>ps.at.txt at> <EOT> job 36 at Mon Dec 16 23:55:00 2013 root@server:~# atq 36 Mon Dec 16 23:55:00 2013 a root root@server:~# ls ps.at.txt uptime.at.txt

Failid

      /var/spool/cron/atjobs
      /var/spool/cron/atspool
      /proc/loadavg
      /var/run/utmp
      /etc/at.allow
      /etc/at.deny

Võtmed (kas on mõtet sisse jätta/targem MAN lugeda ?)

      -V      kuvab versiooni

      -q queue
              uses  the  specified  queue.  A queue designation consists of a
              single letter; valid queue designations range from a to z and A
              to  Z.   The  a queue is the default for at and the b queue for
              batch.  Queues with higher letters run with increased niceness.
              The  special queue "=" is reserved for jobs which are currently
              running.

      If a job is submitted to a queue designated with an  uppercase  letter,
      the  job is treated as if it were submitted to batch at the time of the
      job.  Once the time is reached, the batch processing rules with respect
      to  load average apply.  If atq is given a specific queue, it will only
      show jobs pending in that queue.

      -m      Send mail to the user when the job has completed even if  there
              was no output.
      -M      Never send mail to the user.
      -f file Reads the job from file rather than standard input.
      -t time run the job at time, given in the format [[CC]YY]MMDDhhmm[.ss]
      -l      Is an alias for atq.
      -r      Is an alias for atrm.
      -d      Is an alias for atrm.
      -b      is an alias for batch.
      -v      Kuvab, millal töö käivitatakse, enne töö sisselugemist.
      -c      cats the jobs listed on the command line to standard output.

Vead

      The  correct  operation of batch for Linux depends on the presence of a
      proc- type directory mounted on /proc.

      If the file /var/run/utmp is not available or corrupted, or if the user
      is  not  logged  on  at the time at is invoked, the mail is sent to the
      userid found in the environment variable LOGNAME.  If that is undefined
      or empty, the current userid is assumed.

      At  and  batch as presently implemented are not suitable when users are
      competing for resources.  If this is the case for your site, you  might
      want to consider another batch system, such as nqs.

Kasutatud kirjandus

http://lowfatlinux.com/linux-task-scheduler-at.html
http://linux.about.com/library/cmd/blcmdl1_atq.htm
http://www.brunolinux.com/02-The_Terminal/The_at_Command.html
http://www.computerhope.com/unix/uat.htm
http://www.computerhope.com/unix/ucrontab.htm
http://www.thegeekstuff.com/2010/06/at-atq-atrm-batch-command-examples/
http://en.wikipedia.org/wiki/At_%28Unix%29
http://www.youtube.com/watch?v=gE9oWoKIK6o
http://youtu.be/cDy9kX0Lw7U

Autor

Paul Are AK31, 2013