batch & at commands in Linux

at command

at: We can schedule jobs at a specified time using at command.

atq: This command lists all pending jobs. It shows Job number followed by date time and job class. at -l is similar to atq.

atrm: It is used to deletes a jobs identified by their job number. at -d is similar to atrm.

Examples:

to run a command cat file after 1 minute run the following

$ at now + 1 minute

 at> cat file

ctrl+d

$

Note that after at command we give the date and time when we want to execute the command, then give the commands. It can be a single command or many. To save and exit press ctrl+d.

to run at noon

$ at noon

similarly other ways are

$ at 10 am tomorrow

$ at 11:00 next month

$ at 22:00 today

$ at now + 1 week

The at.allow and at.deny files

The superuser may use these commands in any case. For other users, permission to use at is determined by the files /etc/at.allow and /etc/at.deny.

If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at.

If /etc/at.allow does not exist, /etc/at.deny is there, every username not mentioned in it is allowed to use at.

If neither exists, only the superuser is allowed use of at.

An empty /etc/at.deny means that every user is allowed use these commands, this is the default configuration.

batch Command:

batch: batch executes commands when system load is very low, when the load average drops below 0.8 the system executes the commands.

Example:

$ batch

  command1

  command2

  command3

  CTRL-d

 $

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