top

Additional Notes

top shows a live updating view of system load, CPU usage, memory usage, tasks, and processes. It is useful when a system feels slow or when you need to see which process is consuming resources.

top is interactive. You can press keys while it runs to sort, filter, kill, or change the display.

Syntax

top [options]

Parameters

• options: Flags that change how top behaves.
• pid: Process ID to inspect or signal.
• job: Shell job ID such as %1 when job control is involved.
• command: Command name or pattern to match.

Common Options

• -p PID: Monitor specific process IDs.
• -u USER: Show processes for one user.
• -d SECONDS: Set refresh delay.
• -n COUNT: Exit after a number of updates.
• -b: Batch mode for scripts or log capture.

Useful Interactive Keys

• q: Quit.
• P: Sort by CPU usage.
• M: Sort by memory usage.
• T: Sort by running time.
• k: Kill a process by PID.
• r: Renice a process.
• 1: Toggle per-CPU display.
• c: Toggle full command line.
• h: Show help.

Examples

top

Start live process monitoring.

top -u rani

Show processes owned by user rani.

top -p 1234

Monitor one process.

top -d 1

Refresh every second.

top -b -n 1

Print one batch-mode snapshot and exit.

Reading the Header

• Load average: Roughly shows runnable work over 1, 5, and 15 minutes.
• Tasks: Total, running, sleeping, stopped, and zombie processes.
• CPU line: User, system, idle, wait, and other CPU categories.
• Memory line: Total, free, used, and cache/buffer memory.
• Swap line: Swap usage.

Practical Notes

• High CPU from one process may be normal during builds, compression, scans, or updates.
• High memory usage is not always bad because Linux uses memory for cache.
• CPU wait time can point to disk or storage bottlenecks.
• Use htop if installed for a friendlier interface.
• Use ps for a static snapshot and top for live behavior.