Top

top is a tool to interactively or in batch gather information on processes that run on a system. It has some rather neat features that are not so well known.

This is not a tutorial, just a collection of tricks. You can find a good tutorial on the basic use of top online.

Note that in the tips below, the commands are case sensitive.

1. To select the column on which the processes are sorted, use < to go one column to the left, > to go a column to the right. To highlight the column top currently sorts on, press x (press x again to deactivate highlighting). To reverse the sort order, press R.
2. You can display additional fields besides the default ones, pressing f brings up a screen to select/deselect fields. Press space to select/deselect.
3. A few useful fields that are not shown by default, but that can be quite useful are:
   • nTH = Number of Threads
   • P = Last Used Cpu (SMP)
   • WCHAN = Sleeping in Function
4. To see all threads of a process, press H.
5. If you only want to see processes owned by a given user, press u, and enter the user at the prompt. To exclude processes from a user, use !, e.g., to see all processes not owned by root, use !root.
6. To search for a string in the screen, press L, and use & to find again.
7. To filter the processes show, press either o or O (case insensitive/case sensitive) and enter a search criterion. To remove all filter criteria, press =. These are a few examples of filters you can apply:
   • USER=vsc will show the processes of users that have an ID containing the string ‘vsc’.
   • %MEM>0.5: show processes that consume more than 0.5 % of the available memory.
8. To change the delay time, i.e., the time between screen refreshes, press d and enter the time in seconds.
9. To see summary information for cores, rather than the whole system, press 1, to see summary information per socket, press 2.
10. To save a configuration to disk, press W. This file is .toprc in your home directory.