[Linux] C Shell (csh) renice用法: Adjust process priority

Overview

The renice command in C Shell (csh) is used to change the priority of running processes. By adjusting a process’s priority, you can influence how much CPU time it receives compared to other processes. A lower nice value means higher priority, while a higher nice value means lower priority.

Usage

The basic syntax for the renice command is as follows:

renice [options] [arguments]

Common Options

• -n: Specify the new nice value. This is required to change the priority.
• -p: Change the priority of a process by its process ID (PID).
• -g: Change the priority of all processes in a specified group.
• -u: Change the priority of all processes owned by a specified user.

Common Examples

Here are some practical examples of how to use the renice command:

1. Change the priority of a specific process by PID:

   renice -n 10 -p 1234
   

   This command sets the nice value of the process with PID 1234 to 10.

2. Change the priority of all processes owned by a specific user:

   renice -n -5 -u username
   

   This command lowers the nice value of all processes owned by “username” to -5, giving them higher priority.

3. Change the priority of a process group:

   renice -n 15 -g 5678
   

   This command sets the nice value of all processes in the group with GID 5678 to 15.

4. Check the current nice value of a process:

   ps -o pid,nice,cmd -p 1234
   

   While not part of renice, this command helps you check the current nice value of the process with PID 1234 before making changes.

Tips

• Always check the current nice value of a process before changing it to avoid unintended consequences.
• Use negative nice values cautiously, as they can significantly affect system performance by prioritizing certain processes over others.
• Remember that only the superuser (root) can set a negative nice value; regular users can only increase the nice value (lower priority).