Mastering htop: A Complete Guide to Real-Time System Monitoring

Image source: https://htop.dev/

htop is a command similar to top but with richer features and a friendlier interface, showing real‑time resource usage of processes such as CPU and memory.

When you run htop, the output looks like:

1  [|||||||                                       10.0%]     Tasks: 30, 60 thr; 2 running
  2  [||||||||                                      12.0%]     Load average: 0.29 0.33 0.47
  3  [|||||||                                       10.0%]     Uptime: 01:23:45
  4  [|||||||||                                     15.0%]
  Mem[|||||||||||||||||||||||||||||         1834/7980MB]
  Swp[                                              0/0MB]

  PID USER      PRI  NI  VIRT   RES   SHR S CPU% MEM%   TIME+  Command
    1 root       20   0  225848  9480  6812 S  0.0  0.5  00:02.03 /sbin/init
    2 root       20   0       0     0     0 S  0.0  0.0  00:00.01 [kthreadd]
    3 root       20   0       0     0     0 S  0.0  0.0  00:00.50 [ksoftirqd/0]
    ...

We then parse the output line by line:

First line: 1, 2, 3, 4: CPU core numbers (if multiple cores are present). [||||||| 10.0%]: graphical bar showing each core’s usage; in this example CPU 1 uses 10 %.

Second line: Tasks: 30, 60 thr; 2 running: shows the number of processes, threads, and how many are running. Load average: 0.29 0.33 0.47: system load averages over the past 1, 5, 15 minutes. Uptime: 01:23:45: how long the system has been up.

Third line: Mem[||||||||||||||||||||||||||||| 1834/7980MB]: memory usage bar; 1834 MB used of 7980 MB total. Swp[ 0/0MB]: swap usage; none configured.

Subsequent lines list each process with columns such as PID, USER, PRI, NI, VIRT, RES, SHR, S, CPU%, MEM%, TIME+, and Command, describing their IDs, owners, priorities, memory consumption, state, CPU usage, etc.

In the interactive htop interface, you can use the following keys: F1, h or ?: show help. q or F10: quit htop. F2 or S: open settings to configure display options and colors. F3 or /: search for a process. F4 or \: filter processes. F5 or t: toggle tree view. F6 or < or >: change sorting column. F7 or [: lower the selected process’s priority (increase nice). F8 or ]: raise the selected process’s priority (decrease nice). F9 or k: kill the selected process. Space: mark or unmark a process. u: unmark all processes.

Appendix:

https://github.com/htop-dev/htop