If you call the top command, you get all the running processes. But how can I limit the output only to a certain process name like "java"?
I've tried this top -l 2 | grep java but in this way you get only snapshots and not a continuously updated list. And top -l 0 | grep java is not really clear.
Here's the only solution so far for MacOS:
top -pid `pgrep java | awk 'ORS=" -pid "' | sed 's/.\{6\}$//'`
though this will undesirably report invalid option or syntax: -pid if there are no java processes alive.
EXPLANATION
The other solutions posted here use the format top -p id1,id2,id3, but MacOS' top only supports the unwieldy format top -pid id1 -pid id2 -pid id3.
So firstly, we obtain the list of process ids which have process name "java":
pgrep java
and we pipe this to awk which joins the results with delimitor " -pid "
| awk 'ORS=" -pid "'
Alas, this leaves a trailing delimitor! For example, we may so far have obtained the string "123 -pid 456 -pid 789 -pid ".
We then just use sed to shave off the final 6 characters of the delimitor.
| sed 's/.\{6\}$//'`
We're ready to pass the results to top:
top -pid `...`
get pid of process:
# pidof <process>
tell top what process pid(s) to display
# top -p <pid1>,<pid2>, etc
example:
landis@linux-e6510:~>pidof konsole
1841 1709
landis@linux-e6510:~>top -p 1841,1709
Top will only display the 2 'konsole' processes. This is useful on a busy server via ssh, not having to pipe thru grep.
You need to feed the output of pgrep {proc_name} to top -pid {pid_No}. The problem with top -pid is that it expects -pid before each pid you want to monitor.
On Mac in zsh I can handle this problem e.g. like that:
top `pgrep proc_name | awk '{printf " -pid %d",$1}'`
It's not ideal too, because pgrep looks for substrings in process names. E.g. pgrep dd can return results for icdd, hidd, cloudd etc. The option
pgrep -x should return the exact matches only (like grep -w). But it doesn't work for me in Mac Terminal, although it does in Ubuntu virtual machine.
Using the approach mentioned in the answer by Rick Byers:
top -p `pgrep java | paste -sd "," -`
but I had more than 20 processes running so following command can be helpful for someone who encounter a similar situation.
top -p `pgrep java | head -n 20 | paste -sd "," -`
pgrep gets the list of processes with given name - java in this case. head is used to get first 20 pids because top cannot handle more than 20 pids when using -p argument. Finally paste joins the list of pids with ','.
You can control the process name you are looking for in the above command and the number of processes with that name you are interested to watch. You can ignore the head -n 20 part if the number of your processes with the given name is less than 20.