When you need to see the running processes on your Linux in real time, you have top as your tool for that.
top also displays other info besides the running processes, like free memory both physical and swap
Usage
top [options]
Options
- -d ss.tt
- Delay -- Specifies the seconds and tenths of seconds of delay between the updates of the info showed on the screen, being the default 3 seconds
- -i
- Starts top with the last remembered 'i' state reversed. When this toggle is Off, tasks that are idled or zombied will not be displayed.
- -n n
- Specifies the maximum number of iterations, or frames, top should produce before ending.
- -p n
- Monitor only processes with specified process IDs. This option can be given up to 20 times, or you can provide a comma delimited list with up to 20 pids. Co-mingling both approaches is permitted. This is a command-line option only. And should you wish to return to normal operation, it is not necessary to quit and and restart top -- just issue the '=' interactive command.
- -s
- - Secure - Runs top in secure mode, restricting the commands you can use while top is running even for root
- -S (Sum)
- Starts top with the last remembered 'S' state reversed. When 'Cumulative mode' is On, each process is listed with the cpu time that it and its dead children have used. See the 'S' interactive command for additional information regarding this mode.
Description of the fields
- a: PID -- Process Id
- The task's unique process ID, which periodically wraps, though never restarting at zero.
- b: PPID -- Parent Process Pid
- The process ID of a task's parent.
- c: RUSER -- Real User Name
- The real user name of the task's owner.
VIRT = SWAP + RES.
RES = CODE + DATA.
'D' = uninterruptible sleep
'R' = running
'S' = sleeping
'T' = traced or stopped
'Z' = zombie
Tasks shown as running should be more properly thought of as 'ready to run' -- their task_struct is simply represented on the Linux run-queue. Even without a true SMP machine, you may see numerous tasks in this state depending on top's delay interval and nice value.
When you've chosen to display command lines, processes without a command line (like kernel threads) will be shown with only the program name in parentheses, as in this example:
( mdrecoveryd )
Either form of display is subject to potential truncation if it's too long to fit in this field's current width. That width depends upon other fields selected, their order and the current screen width.
Note: The 'Command' field/column is unique, in that it is not fixed-width. When displayed, this column will be allocated all remaining screen width (up to the maximum 512 characters) to provide for the potential growth of program names into command lines.
Note: By displaying this field, top's own working set will be
increased by over 700Kb. Your only means of reducing that overhead
will be to stop and restart top.
increased by over 700Kb. Your only means of reducing that overhead
will be to stop and restart top.
Interactive commands
While top is running you may issue some options that will interact immediately with top these options are:
- h
- Help, displays a summary of command that will modify the behavior of top
- k
- Kills a process, you will be able to kill only your own processes, unless you are running top as root
- n
- Once this command is entered top will ask you how many lines you want on your screen, if you enter 0 top will display as much as it can
- q
- Exits top
- r
- Change the priority of a process, as well as with k you will only be able to act on your own processes unless you are root
- W
- Writes the current configuration to your personal configuration file, which is $HOME/.toprc