ps

Understanding the Basics

The simplest form of the ps command displays a concise list of processes:

ps

This typically shows the process ID (PID), Terminal (TTY), and command name. However, ps’s true power lies in its numerous options, allowing for highly customized output.

Key Options and Their Usage

Let’s look at some essential ps options:

• -e (or -A): Displays all processes running on the system, including those not associated with a terminal.

ps -e

• -f (full format): Provides a more detailed output, including the process’s parent PID (PPID), session ID (SID), and more.

ps -ef

• -u <username>: Shows processes owned by a specific user. Replace <username> with the actual username.

ps -u john

• -x: Includes processes without controlling terminals. Combining this with -f gives a detailed view.

ps -fx

• --sort=<field>: Sorts the output based on a specified field. Common fields include %CPU (CPU percentage), %MEM (memory percentage), PID, and TIME (CPU time).

ps -eo pcpu,pid,%mem,%cpu --sort=-%cpu
#This sorts by CPU usage in descending order (- signifies descending)

• grep for filtering: Combining ps with grep allows for filtering the output based on process name or other characteristics. This is particularly useful when searching for specific processes.

ps -aux | grep chrome  #Shows all chrome processes

This command first uses ps -aux (similar to ps -e, showing all processes and detailed information) and then pipes the output to grep which filters it to show only lines containing “chrome”.

• awk for data manipulation: awk can be used to further refine and extract specific information from the ps output.

ps -eo pid,%mem,%cpu | awk '{print $1 " " $2 " " $3}'
#This extracts PID, %MEM, and %CPU and prints them in a simplified format.

This example shows how awk can isolate specific columns and arrange them.

Going Deeper: Understanding Output Columns

The output columns often include:

• PID: Process ID – a unique identifier for each process.
• PPID: Parent Process ID – the ID of the process that launched the current one.
• TTY: Terminal associated with the process. A question mark (?) indicates no terminal.
• TIME: CPU time used by the process.
• %CPU: CPU utilization percentage.
• %MEM: Memory utilization percentage.
• CMD: Command used to launch the process.

By mastering the ps command and its various options, you gain a powerful tool for diagnosing performance bottlenecks, identifying resource-intensive processes, and troubleshooting system issues on your Linux systems. Effective use of grep and awk further enhances its analytical capabilities.