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.%MEMrepresents the percentage of memory usage. You can use other fields likeCPU(CPU usage) orPID(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: Runstopin 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.
