at(1) mysteries

[Adri Verhoef]

In article <3920007 at hpirs.HP.COM> carolf at hpirs.HP.COM (Carol Fernihough) has
some questions regarding at(1):
>1) Why isn't /usr/lib/cron/queuedefs described in the documentation

It was posted a while ago:
<>From: guy at gorodish.Sun.COM (Guy Harris)
<>Newsgroups: comp.bugs.sys5
<>Subject: Re: "queuedefs" file format completely undocumented
<>Message-ID: <39786 at sun.uucp>
<>Date: 23 Jan 88 00:42:54 GMT
<>References: <39779 at sun.uucp>
<>Sender: news at sun.uucp
<>Lines: 108
<>
<>Oops!  Wrong name line.  Try this instead:
<>
<>.TH QUEUEDEFS 4
<>.SH NAME
<>queuedefs \- at/batch/cron queue description file
<>.SH SYNOPSIS
<>.LP
<>.B /usr/lib/cron/queuedefs
<>.SH DESCRIPTION
<>The
<>.I queuedefs\^
<>file describes the characteristics of the queues managed by
<>.IR cron (1M).
<>Each non-comment line in this file describes one queue.
<>The format of the lines are as follows:
<>.RS
<>.LP
<>\f2q\f3.\f1[\f2njob\f3j\f1][\f2nice\f3n\f1][\f2nwait\f3w\f1]
<>.RE
<>.LP
<>The fields in this line are:
<>.RS
<>.TP
<>.I q\^
<>The name of the queue.
<>.B a
<>is the default queue for jobs started by
<>.IR at (1);
<>.B b
<>is the default queue for jobs started by
<>.IR batch (1);
<>.B c
<>is the default queue for jobs run from a
<>.B crontab
<>file.
<>.TP
<>.I njob\^
<>The maximum number of jobs that can be run simultaneously in that queue; if
<>more than
<>.I njob\^
<>jobs are ready to run, only the first
<>.I njob\^
<>jobs will be run, and the others will be run as jobs that are currently running
<>terminate.  The default value is 100.
<>.TP
<>.I nice\^
<>The
<>.IR nice (1)
<>value to give to all jobs in that queue that are not run with a user
<>.SM ID
<>of super-user.  The default value is 2.
<>.TP
<>.I nwait\^
<>The number of seconds to wait before rescheduling a job that was deferred
<>because more than
<>.I njob\^
<>jobs were running in that job's queue, or because more than 25 jobs were
<>running in all the queues.  The default value is 60.
<>.RE
<>.LP
<>Lines beginning with
<>.B #
<>are comments, and are ignored.
<>.SH EXAMPLE
<>.RS
<>.nf
<>.ft B
<>a.4j1n
<>b.2j2n90w
<>.RE
<>.fi
<>.ft R
<>.LP
<>This file specifies that the
<>.B a
<>queue, for
<>.I at\^
<>jobs, can have up to 4 jobs running simultaneously; those jobs will be run with
<>a
<>.I nice\^
<>value of 1.  As no
<>.I nwait\^
<>value was given, if a job cannot be run because too many other jobs are running
<>.I cron\^
<>will wait 60 seconds before trying again to run it.
<>The
<>.B b
<>queue, for
<>.I batch\^
<>jobs, can have up to 2 jobs running simultaneously; those jobs will be run with
<>a
<>.I nice\^
<>value of 2.  If a job cannot be run because too many other jobs are running,
<>.I cron\^
<>will wait 90 seconds before trying again to run it.
<>All other queues can have up to 100 jobs running simultaneously; they will be
<>run with a
<>.I nice\^
<>value of 2, and if a job cannot be run because too many other jobs are running
<>.I cron\^
<>will wait 60 seconds before trying again to run it.
<>.SH FILES
<>/usr/lib/cron/queuedefs
<>.SH "SEE ALSO"
<>cron(1M)
<>	Guy Harris
<>	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
<>	guy at sun.com



>   Should the system administrator know
>   what it does and how to modify it?
In general, (s)he should know that there is a manpage, and I think it should be
read and used only when it's really needed, and carefully.