About the batch command

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*Tags*: cmd:batch

http://www.debian-administration.org/users/tong/weblog/6

Newsgroups: gmane.linux.debian.user
Date: Wed, 16 Aug 2006 12:19:50 +0200

The traditional Unix batch command is old and not sexy enough to generate enough talk among the Linux users. However, I recently read a post that hinted the powerfulness of the old utility. To make the long story short, here are my questions, which are not explained clearly in 'man batch':

I know that if I list my tasks one by one and sent to the batch command at once, they'd be executed one by one. But what if I issue 10 different batch commands one by one, which are all scheduled "now", would they still be executed one by one? why?
Which parameter is controlling the sequential execution? What if I want to execute batch commands two at a time?
Would batch jobs compete with CPU resources with my foreground tasks?
Do I need to "nice" the tasks before submitting to batch? If not, what is the default nice value for batch jobs?

About the batch command

> if I issue 10 different batch commands one by one, which are all
> scheduled "now", would they still be executed one by one? why?

Because batch only runs one command at a time. Try it:

$ batch now
> sleep 60
> ^D
$ batch now
> sleep 61
> ^D
$ batch now
> sleep 62
> ^D

Now watch ps auxw

> Would batch jobs compete with CPU resources with my foreground tasks?

Of course. But they only start if the load average is <0.8 Look at nqs otherwise.

> Do I need to "nice" the tasks before submitting to batch?
> If not, what is the default nice value for batch jobs?

You don't have to, or need to, but if you think it would make the system run more smoothly, then do.

Mine run with a niceness of 4, and I haven't changed anything. Try it.

documented on: 2006.09.11