ps: How can i recursively get all child process for a given pid

Question

How can I get the entire process tree spawned by a given process displayed as a tree and only that tree i.e. no other processes?

The output could e.g. look like

 4378 ?        Ss     0:10 SCREEN
 4897 pts/16   Ss     0:00  \_ -/bin/bash
25667 pts/16   S+     0:00  |   \_ git diff
25669 pts/16   S+     0:00  |       \_ less -FRSX
11118 pts/32   Ss+    0:00  \_ -/bin/bash
11123 pts/32   S+     0:00      \_ vi

I couldn't get the desired result purely with parameters to ps.

The following gives the desired result but seems a bit involved:

#!/bin/bash

pidtree() {
  echo -n $1 " "
  for _child in $(ps -o pid --no-headers --ppid $1); do
    echo -n $_child `pidtree $_child` " "
  done
}

ps f `pidtree 4378`

Does anyone have an easier solution?

Answer 1

pstree ${pid}

where ${pid} is the pid of the parent process.

On gentoo pstree is in the package "psmisc," apparently located at http://psmisc.sourceforge.net/

Answer 2

I have been working to find a solution to the exact same problem. Bascially, ps manpage does document any option allowing to do what we want with a single command. Conclusion: a script is needed.

I came up with a script very similar to yours. I pasted it in my ~/.bashrc so I can use it from any shell.

pidtree() {
  local parent=$1
  local list=
  while [ "$parent" ] ; do     
    if [ -n "$list" ] ; then
      list="$list,$parent"
    else
      list="$parent"
    fi
    parent=$(ps --ppid $parent -o pid h)
  done
  ps -f -p $list f
}