How to use the command `batch` (with examples)
The batch command allows users to execute commands at a later time when the system load levels permit. The command relies on the atd (or atrun) service to execute the commands. The batch command is useful in situations where certain tasks need to be carried out when the system is less busy, optimizing system resources and performance.
Use case 1: Execute commands from stdin (press Ctrl + D when done)
Code:
batch
Motivation:
One scenario where executing commands from stdin may be useful is when a user has a set of commands that they want to run as a batch, but they don’t need to execute them immediately. By using the batch command, they can input the commands from the standard input, allowing them to specify the commands one by one, and then execute them later when the system load is lower.
Explanation:
In this use case, the batch command is executed without any additional arguments. It prompts the user to enter the commands from the standard input. The user can input multiple commands and press Ctrl + D when they have finished entering the commands. The batch command then schedules the execution of these commands for a later time when the system load levels permit.
Example output:
batch>
ls -l
rm file.txt
Ctrl + D
The commands ls -l and rm file.txt are entered from the standard input. Once the user presses Ctrl + D, the commands are scheduled to be executed at a later time.
Use case 2: Execute a command from stdin
Code:
echo "./make_db_backup.sh" | batch
Motivation:
In some cases, there may be a need to execute a command specified in a file, which can be passed as input to the batch command. This approach can be useful when there is a need to schedule the execution of a specific command stored in a file, rather than typing it directly into the terminal.
Explanation:
In this use case, the echo command is used to output the command ./make_db_backup.sh. The output from echo is then piped (|) to the batch command. The batch command takes the input from the pipeline and schedules the execution of the specified command at a later time.
Example output:
batch>
./make_db_backup.sh
The command ./make_db_backup.sh is passed as input using the echo command and piped to the batch command. The batch command then schedules the execution of this command for a later time.
Use case 3: Execute commands from a given file
Code:
batch -f path/to/file
Motivation:
Sometimes, it is necessary to execute a set of commands stored in a file. With the batch command, users can easily schedule the execution of commands saved in a specific file. This can be useful in situations where there is a need to automate a series of commands and schedule their execution at a later time.
Explanation:
In this use case, the -f option is used to specify the path to a file containing the commands to be executed. The batch command reads the commands from the specified file and schedules their execution at a later time.
Example output:
batch>
Command file is executed successfully.
The commands stored in the file specified with the -f option are read by the batch command and scheduled for later execution. Upon successful execution, a confirmation message is displayed.
Conclusion:
The batch command is a versatile tool for scheduling the execution of commands at a later time when the system load levels permit. Whether inputting commands from stdin, executing a specific command from stdin, or running commands from a file, the batch command provides users with flexibility in managing and automating tasks.
