How do you use top to monitor processes interactively?

Question

Accepted Answer

top is an interactive, continuously-refreshing process monitor — a live view of CPU, memory, load, and the busiest processes.
Where ps is a single snapshot, top updates every couple of seconds, so it's what you open to catch what's happening right now — which process is pegging the CPU, whether you're swapping, how loaded the box is. It's interactive: keys re-sort and filter the live display.
What the header shows:

system uptime and the 1/5/15-minute load average
CPU breakdown (user vs system vs idle vs iowait)
memory and swap usage
the process list, sorted by CPU% by default

Interactive commands:

Key
Action

q
Quit

h
Help

M
Sort by memory

P
Sort by CPU

k
Kill a process (enter PID)

r
Renice a process

u
Filter by user

1
Show individual CPUs

c
Show full command

Load average: 1min, 5min, 15min

Load = number of processes wanting CPU
Load 1.0 on 1 CPU = 100% utilized
Load 4.0 on 4 CPUs = 100% utilized

Alternative: htop is more user-friendly (may need to install).

Key	Action
`q`	Quit
`h`	Help
`M`	Sort by memory
`P`	Sort by CPU
`k`	Kill a process (enter PID)
`r`	Renice a process
`u`	Filter by user
`1`	Show individual CPUs
`c`	Show full command