Cheatsheet & Examples: top

Cheatsheet & Examples: top

top is a command-line utility that provides a dynamic, real-time view of running processes in a Unix-like operating system. It displays information about CPU and memory usage, process IDs, and other system statistics, allowing users to monitor system performance and identify resource-intensive processes.

Monitoring System Processes (Default View)

Example Usage: top

What it does: Displays a constantly updated, interactive view of running processes, sorted by CPU usage. This is the basic, no-frills way to invoke top.

Command-line Arguments Explained:

This basic usage doesn't include any arguments.

Sorting by a Different Field

Example Usage: top -o %MEM

What it does: Displays processes sorted by memory usage (%MEM).

Command-line Arguments Explained:

-o %MEM: Specifies the field to sort by. %MEM represents the percentage of memory usage. You can use other fields like CPU (CPU usage) or PID (process ID).

Updating Delay

Example Usage: top -d 5

What it does: Updates the display every 5 seconds. The default update interval is typically 3 seconds.

Command-line Arguments Explained:

-d 5: Sets the delay between screen updates to 5 seconds. The value is specified in seconds.

Batch Mode

Example Usage: top -b -n 1

What it does: Runs top in batch mode, outputting the results to standard output and then exiting after a specified number of iterations (in this case, 1). This is useful for capturing a snapshot of system activity.

Command-line Arguments Explained:

-b: Runs top in batch mode.
-n 1: Specifies the number of iterations to run. After the specified number of iterations, top exits.

Filtering by User

Example Usage: top -u username

What it does: Displays only the processes owned by the specified username.

Command-line Arguments Explained:

-u username: Filters the display to show processes owned by the user "username". Replace "username" with the actual username.

Displaying Command Lines

Example Usage: top -c

What it does: Toggles the display of the full command lines for each process. This can be helpful to understand what arguments a process was run with.

Command-line Arguments Explained:

-c: Toggles the display of the full command line. Pressing 'c' while top is running will also achieve the same result.

Highlighting

Example Usage: top -H

What it does: Highlights the current process being viewed with a different color.

Command-line Arguments Explained:

-H: Highlights the current process being viewed with a different color.