Unix batch Command

The batch command executes commands entered from standard input. This command functions much like the at command. However, one key difference exists: at can execute several commands at once, running them in the background. This operation can consume valuable system resources and bog down the server. The batch command runs one process, waits for it to end, then runs another. This empowers the operating system to run batch jobs and tasks at its own discretion, rather than being forced to run them at a specific time. The command syntax for batch is as follows:

batch task list CTRL+D

Although you can issue commands to view crontab and at entries, you must rely on email to receive output for the batch command.

Batch Processes

Batch processes are not associated with any terminal. Rather, they are submitted to a queue, from which jobs are executed sequentially. Unix offers a very primitive batch command, but vendors whose customers require queuing have generally implemented something more substantial. Some of the best known are the (NQS) Network Queuing System^[1], developed by NASA and used on many high-performance computers including Crays, as well as several network-based process-scheduling systems from various vendors. These facilities usually support heterogeneous as well as homogeneous networks, and they attempt to distribute the aggregate CPU load evenly among the workstations in the network, a process known as load balancing or load leveling.

[1](NQS) Network Queuing System: The Network Queueing System(NQS) was created by the need for a UNIX batch and device queueing facility capable of supporting requests in a networked environment of UNIX machines. Furthermore, NQS was developed as part of an effort aimed at tying together a diverse assortment of UNIX based machines into a useful computational complex for the National Aeronautics and Space Administration (NASA).