"at" command

jiya_31 · 10-18-2007, 11:48 PM

i need to make my process execution terminal free.
For this i can run them using "at" command. But to execute directly without reading the command from a file i use = at 'time' and press ENTER, then, at> (at prompt) appears on the screen on which i write the command to be executed.
Though this solves my purpose by my aim to attain the same functionality programatically.I dont want to type everything on the console and do it. can anybody suggest me, how to do that exceot using scripts?

PAix · 10-19-2007, 01:07 AM

Hi and welcome,

Not quite sure what you are doing, but from what you say you seem to be invoking the at program as follows, and then hitting ctl+D to facilitate exit from the at program.

Code:

yourprompt> at 08:00
at> programname
at> <EOT>
job 20 at 2007-10-19 09:00
yourprompt>

I imagine that the screen looks a bit like that.

if you try this

Code:

yourprompt> at -f programname 09:00
warning: commands will be executed using /bin/sh
job 21 at 2007-10-19 09:00

The warning can be redirected to /dev/null or a log file if required.

Code:

yourprompt> at -f programname 09:00 2> /dev/null
yourprompt>

You needn't launch the real program, but could launch a script that calls the real program. My requirement at home is trivial, the batch program can't run sound, but the program it calls can utilise the sound card, a trivial Morse beacon program that reads a serial number from a file, increments the serial number and writes it back and writes the obtained serial number into a short beacon message replete with transmitter callsign etc At the end of the program II also have the program re queue itself five minutes later as long as either the serial number hasn't exceeded a set limit or the time of day exceeds a set limit. The world is your oyster.

I hope that I have given the information that you seek and I will of course look back later in the day to check if you have any further issues on the subject that I might help you with. The at man page should give you more than a few clues about expressing time for execution. So that's you virtually busy during your next holiday then. All you have to do is get the box to email the boss each day you are sipping lemonade in the sun, to tell him that the system is fine, the financials run is complete and what a good job you are doing in the engine room.

PAix

jschiwal · 10-19-2007, 01:09 AM

Quote:

i need to make my process execution terminal free.

It would be easier to read your question if you capitalized the personal pronoun "I".

If you are using "at" simply because you want to be able to log off and have the program continue, then you can use "nohup" or "screen". Nohup will detach the terminal and log the output to a file. Screen allows you to detach the console and later re-attach it.

You might also want to read up on using cron. Also, many programs have --quiet options to prevent terminal output, but you can still redirect any input or output of a script to a file or /dev/null to allow it to run as a cron job.

bigearsbilly · 10-19-2007, 02:19 AM

Code:

at now <<EOF
date
ls
EOF

Code:

echo /bin/date | at now

useful for reminders...

Code:

at midnight <<EOF
cat
don't forget to put 
the cat out
`date`
EOF

PAix · 10-20-2007, 08:50 AM

Quote:

You might also want to read up on using cron.

Please correct me if I am at all wrong in anything I say.

I seem to recollect that a minor difficulty that I encountered using cron on a Solaris box was that cron doesn't use the environment of the user, so additional work has to be done to ensure that the test running done during development in a rich environment holds good when exposed to the austere environment in which cron actually runs.

I believe also that there is an anomally (untested) in the way SUSE 10.* handles jobs. Is there a problem with running a job at the same time each day? I have a feeling that it is a bit cavalier in the way it handles the timing. Perhaps someone can enlighten us here.

The attraction of at is that it runs in the familiar user environment and so is relatively facile to implement.

PAix

bigearsbilly · 10-22-2007, 02:55 AM

cron doesn't guarantee to run on time I don't think.

I used to run suse for years and years and I found it intensely irritating all the cron jobs
it would have by default, you'd be sitting there and then notice your disk spinning away
and your cpu load up while it was doing an updatedb or a find or some other nonsense
I didn't ask for.
In the end I just gzipped the scripts up to stop them running.
(I didn't rm them in case I regretted it)