How to use the command 'nice' (with examples)

The nice command in Unix-like operating systems enables users to launch programs with a specified priority level. By adjusting a program’s “niceness,” users can influence how much CPU time the program receives relative to other processes. Niceness values range from -20, which represents the highest priority, to 19, the lowest. This capability is crucial when managing system resources, ensuring that crucial processes receive adequate CPU time while less important tasks do not hinder system performance. For more details, you can visit the official GNU documentation: GNU Coreutils Nice .

Use case 1: Launch a program with altered priority

Code:

nice -10 my_script.sh

Motivation:

In a multi-tasking operating system, resource management is key to maintaining optimal performance and system responsiveness. Suppose you need to run a script, my_script.sh, that is not time-critical. By default, processes are launched with a niceness value of 0. However, by setting a positive niceness value like 10, you lower the priority of this script. This ensures it does not interfere with other more urgent processes that need CPU resources, such as real-time data processing or interactive applications.

Explanation:

• nice: This is the command used to start a program with a modified scheduling priority.
• -10: This argument specifies the desired niceness value. Here, 10 is used, indicating a lower priority than the default (0).
• my_script.sh: This is the program or script you wish to execute with the specified niceness value.

Example output:

Script started with niceness 10. The process may run slower if system is heavily loaded.

Use case 2: Define the priority with an explicit option

Code:

nice -n 5 gzip largefile.tar

Motivation:

When working with large files, such as compressing largefile.tar using gzip, the operation can be resource-intensive and may slow down other critical processes or system operations. By explicitly setting a niceness value using the -n (or --adjustment) option, you can ensure this resource-heavy task runs with reduced priority. This keeps your system from becoming unresponsive while compressing large files, maintaining a balance between completing this task and running other essential programs.

Explanation:

• nice: The base command to modify process scheduling priority.
• -n 5: The -n (or its long form --adjustment) option explicitly defines the niceness value. Here, 5 is chosen to slightly reduce the task’s priority.
• gzip largefile.tar: This is the command to compress the file largefile.tar. The niceness adjustment is applied to this specific command, ensuring that while it runs, the system knows to prioritize other tasks with default or higher priority.

Example output:

Compressing 'largefile.tar' with niceness 5. System remains responsive to other tasks.

Conclusion:

The nice command is an essential tool for managing CPU resource allocation in Unix-like systems. By adjusting the niceness value of a program, you gain finer control over how processes share the CPU, allowing you to optimize performance based on task importance. Whether you’re running time-insensitive scripts or handling resource-intensive operations, utilizing nice helps maintain a stable system environment, ensuring that essential tasks receive the attention they need without unnecessary interference from less critical processes.