Using the Linux top Command for Real-Time System Monitoring

The top command provides a dynamic, real‑time view of Linux system processes and resource usage, similar to Windows Task Manager.

It displays overall system statistics in the first few lines, including current time, uptime, number of users, and load averages.

Subsequent lines show CPU usage breakdown (us, sy, ni, id, wa, hi, si, st) and memory statistics (total, free, used, buff/cache) as well as swap information.

Process information includes columns such as PID, USER, PR, NI, VIRT, RES, SHR, S, %CPU, %MEM, TIME+, and COMMAND. The default view can be customized with interactive keys.

Common top options:

top [-] [d] [p] [q] [C] [S] [s] [n]

-d
Set refresh interval (default 5 s)

-p
Show only specified process

-b -n 2 > /tmp/top.txt   Batch mode, output two iterations to a file

-S             Cumulative mode

-s             Secure mode

-i             Hide idle and zombie processes

-c             Show full command line

Interactive shortcuts allow sorting by %CPU (P), %MEM (M), TIME+ (T), changing sort order (R), selecting columns (f), swapping column order (o), and choosing sort columns (F).

CPU steal time (%st) is important for virtualized environments (e.g., EC2). A high %st indicates the VM is waiting for physical CPU resources.

Monitoring %id (idle) and %wa (I/O wait) together with %st helps assess CPU load and potential bottlenecks.