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ps – Report Current System Process Status

The ps command is a Linux utility that reports the current system process status. It is used to display information about the processes running on the system, including their process ID (PID), CPU usage, memory usage, and other details. This command is commonly used by system administrators to monitor the system and troubleshoot issues related to processes.

Overview

The basic syntax of the ps command is as follows:

ps [options]

When executed without any options, the ps command displays information about the processes that are running in the current terminal session. The output includes the PID, TTY, TIME, CMD, and other details.

Here are some common use cases for the ps command:

  • To display information about all processes running on the system, use the following command: 
    ps -ef
  • To display information about all processes running in the current terminal session, use the following command: 
    ps
  • To display a hierarchical tree of processes, use the following command: 
    ps axjf
  • To display information about a specific process, use the following command: 
    ps -p <pid>
  • To display detailed information about a specific process, use the following command: 
    ps -p <pid> -o pid,ppid,user,%cpu,%mem,cmd

Here are some examples of the output of the ps command:

  PID TTY          TIME CMD
  1234 pts/0    00:00:00 bash
  5678 pts/0    00:00:00 ps

Options

The ps command supports a wide range of options that allow you to customize the output and filter the results. Here is a table of the most commonly used options:

Option Description
-a Displays information about all processes, including those of other users.
-e Displays information about all processes, including those that are not associated with a terminal.
-f Displays a full listing of all processes, including the UID, PPID, C, STIME, TTY, TIME, and CMD.
-h Hides the header from the output.
-p Displays information about a specific process, identified by its PID.
-u Displays information about all processes that are being run by a specific user.
-x Displays information about all processes, including those that are not associated with a terminal.

Troubleshooting Tips

Here are some common issues that you may encounter when using the ps command, along with solutions to those issues:

  • The output is too long to read. In this case, you can use the less command to scroll through the output one page at a time. For example: 
    ps -ef | less
  • The output is missing important information. In this case, you can use the -o option to specify which columns to display. For example: 
    ps -ef -o pid,ppid,user,%cpu,%mem,cmd
  • The output is not sorted in a useful way. In this case, you can use the sort command to sort the output based on a specific column. For example: 
    ps -ef | sort -k 3

Notes

  • The ps command is a powerful tool for monitoring the system and troubleshooting issues related to processes. However, it is important to use it with caution, as it can potentially display sensitive information about the system and its users.
  • The output of the ps command may vary depending on the version of Linux you are using. It is recommended to refer to the manual page for your specific version of Linux for more information.

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