top Command
Beginner Process Management man(1)Display real-time system resource usage and processes
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📅 Updated: Mar 15, 2026
SYNTAX
top [OPTION]...
What Does top Do?
top provides a real-time, dynamic view of running processes sorted by CPU usage. It is the standard tool for monitoring system resource consumption including CPU, memory, swap, and load averages.
top updates its display at regular intervals (default 3 seconds), showing process ID, user, CPU percentage, memory percentage, and command for each process. The header area shows system-wide statistics including uptime, load averages, CPU states, and memory usage.
top supports interactive commands for sorting, filtering, killing processes, and changing display options. It is the go-to tool for identifying what is consuming system resources.
top updates its display at regular intervals (default 3 seconds), showing process ID, user, CPU percentage, memory percentage, and command for each process. The header area shows system-wide statistics including uptime, load averages, CPU states, and memory usage.
top supports interactive commands for sorting, filtering, killing processes, and changing display options. It is the go-to tool for identifying what is consuming system resources.
Options & Flags
| Option | Description | Example |
|---|---|---|
| -d | Set update interval in seconds | top -d 1 |
| -p | Monitor specific PIDs only | top -p 1234,5678 |
| -u | Show only processes for a user | top -u www-data |
| -b | Batch mode (for scripting/logging) | top -bn 1 > top_output.txt |
| -n | Number of iterations before exit | top -bn 5 |
| -H | Show individual threads | top -H |
| -i | Hide idle processes | top -i |
| -o | Sort by field | top -o %MEM |
| -c | Show full command line | top -c |
Practical Examples
#1 Standard monitoring
Opens real-time process monitor. Press q to quit.
$ top#2 Fast refresh
Updates every 1 second for real-time monitoring during incidents.
$ top -d 1#3 Monitor specific user
Shows only processes owned by the www-data user.
$ top -u www-data#4 Single snapshot for logging
Batch mode captures one snapshot — useful for logging and scripts.
$ top -bn 1 | head -20#5 Monitor specific PIDs
Monitors only the specified process IDs.
$ top -p 1234,5678#6 Sort by memory
Starts top sorted by memory usage instead of CPU.
$ top -o %MEMTips & Best Practices
Interactive shortcuts: While in top: M=sort by memory, P=sort by CPU, k=kill process, r=renice, c=toggle full command, 1=show per-CPU, q=quit.
Load average explained: Load average shows 1/5/15 minute averages of processes wanting CPU. On a 4-core system, load 4.0 means 100% utilization. Above core count indicates overload.
%CPU can exceed 100%: On multi-core systems, a process can show >100% CPU — it means it is using multiple cores. 200% = 2 full cores.
Frequently Asked Questions
How do I sort by memory usage?
Press M while in top, or start with top -o %MEM. Press P to switch back to CPU sorting.
How do I kill a process from top?
Press k, enter the PID, then enter the signal (15 for graceful, 9 for force kill).
What is the difference between top and htop?
htop has a better UI with colors, mouse support, horizontal/vertical scrolling, tree view, and easier process management. htop is top with a better interface.
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