#!/bin/bash
#
# $Id$
#
# phier: Show process tree incorporating a process.
# Notes: phier functions similarly (but not identically) to Solaris ptree.
# Usage: phier [options] <pid>
# Options: -s <search>   Stop hierarchy at this process name.
# Example: phier -s sshd $$
#

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

  if [ -z "$child" ]; then
    echo >&2 "No child to find."
    return 1
  fi

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

  find_parent $ppid $top
  return $?
}

# Parse arguments.
top=
while getopts ":s:" opt; do
  case $opt in
    s) top="$1";;
  esac
done
shift $((OPTIND-1))

if [ $# -lt 1 ]; then
  echo >&2 "phier: Print process hierarchy for a process."
  echo >&2 "Usage: phier [options] <pid>"
  echo >&2 "Options: -s <search>   Stop hierarchy at this process name."
  echo >&2 "Example: phier -s sshd $$"
  exit 1
fi

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