Cheatsheet & Examples: ps

The ps command reports information about the current processes running on a Unix-like system. It is used to monitor, manage, and debug process activity.

Display processes for the current terminal session

Example Usage: ps

What it does: Shows a list of processes associated with the current terminal session, including the process ID (PID), terminal, CPU usage, and command name.

Command-line Arguments Explained:

• None: Defaults to showing processes for the current user and terminal session.

Display a detailed list of all processes

Example Usage: ps aux

What it does: Provides a comprehensive list of all running processes, including user, CPU, memory, and command-line details.

Command-line Arguments Explained:

• a: Displays processes for all users.
• u: Shows user-oriented format with detailed resource usage.
• x: Includes processes without a controlling terminal (background processes).

Display all processes in a full format

Example Usage: ps -ef

What it does: Lists all processes in a detailed format, including the user, PID, parent PID, CPU usage, and command.

Command-line Arguments Explained:

• -e: Selects all processes.
• -f: Displays the full format listing (long format).

Display processes by PID

Example Usage: ps -p [PID]

What it does: Shows information about a specific process using its process ID (PID).

Command-line Arguments Explained:

• -p: Specifies the process ID to monitor.

Display processes in long format

Example Usage: ps -l

What it does: Shows process details in a long format, including PID, PPID, command, and resource usage.

Command-line Arguments Explained:

• -l: Enables long (detailed) listing format.

Display processes with custom output fields

Example Usage: ps -o [field1],[field2]

What it does: Customizes the output to display only specified fields, such as PID, command, or memory usage.

Command-line Arguments Explained:

• -o: Defines custom output fields. Replace [field1],[field2] with desired fields like pid,comm,mem.

Sort processes by CPU usage

Example Usage: ps -eo %cpu,comm --sort -%cpu

What it does: Lists processes sorted by CPU usage in descending order, highlighting the most resource-intensive tasks.

Command-line Arguments Explained:

• -e: Selects all processes.
• -o: Specifies output fields, e.g., %cpu (CPU percentage) and comm (command name).
• --sort: Sorts the output by the specified field ( - denotes descending order).

Display processes owned by a specific user

Example Usage: ps -u [username]

What it does: Lists processes owned by the specified user, showing their resource usage and command details.

Command-line Arguments Explained:

• -u: Displays processes for the given username. If no username is provided, it defaults to the current user.

Display process tree structure

Example Usage: ps --forest

What it does: Generates a tree-like view of processes, showing parent-child relationships.

Command-line Arguments Explained:

• --forest: Displays processes in a hierarchical tree format, with indentation for child processes.

Display threads of a specific process

Example Usage: ps -T -p [PID]

What it does: Lists all threads associated with the specified process, including thread IDs (TID) and related details.

Command-line Arguments Explained:

• -T: Shows threads instead of processes.
• -p: Specifies the process ID to monitor.

Display processes with their start time and command line

Example Usage: ps -eo pid,etime,cmd

What it does: Shows the PID, elapsed time, and full command line for all processes.

Command-line Arguments Explained:

• -e: Selects all processes.
• -o: Customizes output to include pid (process ID), etime (elapsed time), and cmd (command line).

Filter processes by command name

Example Usage: ps -C [command_name]

What it does: Displays processes matching the specified command name, such as nginx or bash.

Command-line Arguments Explained:

• -C: Filters processes by the exact command name provided. Use --help to view supported options.