How to display only a process and its descendant processes on htop?

Question

I want to monitor only a process and its children processes on htop. Filtering on the name of the parent process lists only the parent process, not its children. How do I show the children processes too?

Answer 1

Under Linux, you can do:

htop -p `pstree -p $PID | perl -ne 'push @t, /\((\d+)\)/g; END { print join ",", @t }'`

where $PID is the root process. This works as follows:

1. The list of the wanted processes are obtained with pstree, using the -p option to list them with their PID.
2. The output is piped to a Perl script that retrieves the PID's, using a regular expression (here, \((\d+)\)), and outputs them separated with commas.
3. This list is provided as an argument of htop -p.

For other OS like Mac OS, you may need to adapt the regular expression that retrieves the PIDs.

Note: It is unfortunately not possible to update the list with new children that are spawn later, because once htop has been executed, one cannot do anything else. This is a limitation of htop (current version: 2.0.2).

Answer 2

htop -p $(ps -ef | awk -v proc=$PID 'BEGIN{pids[proc]=1;printf "%s",proc} {if(pids[$3]==1){printf ",%s",$2; pids[$2]=1}}')

Where $PID is the root process id.

Use awk to create a comma separated list of the specified process and its descendant processes and pass the output to htop -p.

Answer 3

htop -p $(ps -ef | awk -v proc=15305 '$3 == proc { cnt++;if (cnt == 1) { printf "%s",$2 } else { printf ",%s",$2 } }')

Use awk to create a comma separated list of process id's from the output of ps -ef passing the parent process id as proc and then passing this out to htop -p.

Answer 4

on macOS (prolly works on linux too), a potential workaround that works for me is to identify a search phrase for each process in the hierarchy and use htops FILTER pattern to search for each term separated by a |. this allows a live monitor that captures child processes too as long as part of your search pattern captures the child process.

so if you have the following process hierarchy you want to monitor:

top-process-A
\__ subprocess-B
    \__ subsubprocess-C
        \__ subsubsubprocess-D

use the FILTER pattern A|B|C|D.

If the patterns are less specific, this might capture some other processes you dont care about, but it will drastically reduce the number of visible processes in the current viewport. this might be untenable though the more processes you are trying to monitor, especially if they all have different names.