We can view the dynamic information of all processes through two tools, top and htop, which support interactive viewing of processes.

top

The top command is a tool that can view processes in real time.

Options for top command

Here are some options for the task window.

Option	Description
-b	Run top in batch mode.
-d N	Refresh task window in every N seconds.
-n	Limit the number of batches produces by top.

Here are some interactive commands for the top interactive interface.

Here are some summary global commands for the task window.

Command	Description
d or s	Change the refresh the task window in every N seconds.
k	Kill the process which ID matches the specified integer number.
q	Quit the task windows.

Here are some summary area commands for the task window.

Command	Description
l	Shows or hides the average load and system uptime.
t	Show or hide tasks and CPU summary information.
m	Show or hide memory and swap memory usage.
1	Show all CPU usage summaries individually or jointly.

Here are some descending sorting commands for the task window.

                    
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                          top    # This will show the interactive task window

Here are the explanations of the highlighted columns:

Column	Description
PID	The unique process ID of the task.
USER	Valid user name of the task owner.
PR	The priority of the task.
NI	The value of priority, the higher the value, the lower the priority.
VIRT	The size of virtual memory used by the task.
RES	The size of the non-swapped physical memory used by the task.
SHR	The size of shared non-swapped physical memory that may be used by other processes
S	The process state of the task. Possible states are: D (uninterruptible sleep), I (idle), R (running), S (sleeping), T (stopped by job control signal), t (stopped by debugger during trace), Z (zombie)
%CPU	The CPU usage percentage of the task.
%MEM	The memory usage percentage of the task.
TIME+	The CPU time consumed by the task.
COMMAND	The command name or command line used to start the task.

The htop command is an easier-to-use top tool.

We need to install this tool first:

                    
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                          yum install htop -y

Here are some options for the task window.

Option	Description
-d or ‑‑delay=DELAY	Sets the interval to refresh the task window every tenths of seconds.
-C or ‑‑no-color or ‑‑no-colour	Displays the task window in black and white.
-p or ‑‑pid=PID,PID,…	Displays only those processes that match the specified process IDs.
-s or ‑‑sort-key COLUMN	Sort processes by the COLUMN.
-u or ‑‑user=USERNAME	Output only the processes own by the USERNAME.
-t or ‑‑tree	Output processes command name in a tree view format.

Here are some interactive commands for the top interactive interface:

Command	Description
F1 or h or ?	Show the help screen.
F2 or S	Show the setup screen. We can configure the meters, options and column appearance of the summary area.
F3 or /	Highlighted the processes which their command name match the specified content. Press F3 for ongoing matches.
F4 or	Output the processes which their command name match the specified content.
F5 or t	Output processes command name in a tree view format.
F6	Choose a column to be sorted.
F7 or ]	Raise a selected process’s priority.
F8 or [	Reduce a selected process’s priority.
F9 or k	Kill a process matches the specified process ID.
F10 or q	Quit the task window.
I	Reverse the sort order.
u	Output only the processes owned by a specified user.
M	Sort by memory usage.
P	Sort by CPU usage.
T	Sort by consumed time.
p	Show or hide the full path of the command used to start the process.
Ctrl+L	Refresh the task window manually.

References TOP(1), HTOP(1)