Find ancestor and descendant of a process on Linux.

find_ancestor_children.sh

#!/bin/sh

find_ancestors() {
  pid=$1

  while [ "$pid" -ne 0 ]; do
    echo "$pid"
    pid=$(awk '{print $4}' /proc/"$pid"/stat 2>/dev/null)
  done
}

find_children() {
  parent_pid=$1
  children=$(awk -v ppid="$parent_pid" '$4==ppid {print $1}' /proc/[0-9]*/stat 2>/dev/null)

  for child in $children; do
    echo "$child"
    find_children "$child"
  done
}

find_ancestors "$1"
find_children "$1"