#!/bin/bash

function find_parent() {
  child="$1"; shift
  top="$1"; shift

  cmd=$(ps -o comm= -p $child)
  pid=$(ps -o pid= -p $child)
  ppid=$(ps -o ppid= -p $child)

# echo >&2 "Finding from $child ($top) $pid/$ppid/$cmd"

  if [ -z "$pid" ]; then
    echo >&2 "Can't find PID $child!"
    return 1
  fi

  if [ ! -z "$top" ]; then
    if [ "$cmd" = "$top" ]; then
      echo $child
      return 0
    fi
  fi

  if [ $ppid = 1 ]; then
    echo $pid
    return 0
  fi

  find_parent $ppid $top
  return $?
}

if [ $# -lt 1 ]; then
  echo >&2 "phier: Print process hierarchy for a process."
  echo >&2 "Usage: phier <pid> [<search>]"
  echo >&2 "Notes: If a search term is given the hierarchy will stop after finding a"
  echo >&2 "       process matching that search term."
  echo >&2 "Example: phier $$ sshd"
  exit 1
fi

parent=$(find_parent ${1+"$@"})
if [ $? = 0 ]; then
  pstree -ulap $parent
else
  exit 1
fi