Top

The Linux top command provides a terminal task manager which lists all of the running processes on the computer.

top

I use “Top” to kill a process within the top interface simply press k and enter the process id next to the application you wish to close. Top solicits a specific signal to send; in most cases, enter 15 (to request the process to gracefully terminate) or 9 (to immediately kill the process).


The first line offers some basic high-level info about the system:

  • The time
  • How long the computer has been running
  • Number of users
  • Load average

The load average shows the system load time for the last 1, 5 and 15 minutes.


The second line summarizes the number of ongoing, concurrent tasks:

  • Total number of tasks
  • Number of running tasks
  • Number of sleeping tasks
  • Number of stopped tasks
  • Number of zombie tasks

The third line summarizes CPU performance:

  • usage by the user
  • usage by system
  • usage by low priority processes
  • usage by idle processes
  • usage by io wait
  • usage by hardware interrupts
  • usage by software interrupts
  • usage by steal time

The fourth line emphasizes memory:

  • Total system memory
  • Free memory
  • Memory used
  • Buffer cache

The fifth line highlights available swap space and total memory inclusive of swap:

  • Total swap available
  • Total swap free
  • Total swap used
  • Available memory

Main Table

The main table lists running processes:

  • Process ID
  • User
  • Priority
  • Nice level
  • Virtual memory used by process
  • Resident memory used by a process
  • Shareable memory
  • CPU used by process as a percentage
  • Memory used by process as a percentage
  • Time process has been running
  • Command

Key Switches For the ‘top’ Command

Although you invoke top just by typing the name in a shell session, a few switches modify the utility’s behavior:

  • -h: Show the current version
  • -c: This toggles the command column between showing command and program name
  • -d: Specify the delay time between refreshing the screen
  • -o: Sorts by the named field
  • -p: Only show processes with specified process IDs
  • -u: Show only processes by the specified user
  • -i: Do not show idle tasks
Share with your friends!

Leave a Reply

Your email address will not be published. Required fields are marked *