#!/bin/bash
#
# $Id$
#
# phier: Show process tree incorporating a process.
# Notes: phier functions similarly (but not identically) to Solaris ptree.
# Usage: phier [-s <search>] <pid>
# Usage: phier [-s <search>] [-u <user>] [-x] <process>
# Options: -s <search>   Stop hierarchy at this process name.
#          -u <user>     Start search from processes owned by user.
#          -x            Match process name exactly.
# Example: phier -s sshd $$
# Example: phier -s sshd -u iain nxagent
#

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.
children=
top=
pgrep_opts=
while getopts ":s:u:x" opt; do
  case $opt in
    s) top="$OPTARG";;
    u) pgrep_opts="$pgrep_opts -u $OPTARG";;
    x) pgrep_opts="$pgrep_opts -x"
  esac
done
shift $((OPTIND-1))

if [ $# -lt 1 ]; then
  echo >&2 "phier: Print process hierarchy for a process."
  echo >&2 "Usage: phier [-s <search>] <pid>"
  echo >&2 "Usage: phier [-s <search>] [-u <user>] [-x] <process>"
  echo >&2 "Options: -s <search>   Stop hierarchy at this process name."
  echo >&2 "         -u <user>     Start search from processes owned by user."
  echo >&2 "         -x            Match process name exactly."
  echo >&2 "Example: phier -s sshd $$"
  echo >&2 "Example: phier -s sshd -u iain nxagent"
  exit 1
fi

children="$1"; shift
if ! echo "$children" | grep -qs '^[0-9]*$'; then
  children=$(pgrep $pgrep_opts "$children")
fi

errors=0
for child in $children; do
  parent=$(find_parent "$child" "$top")
  if [ $? = 0 ]; then
    pstree -ulap $parent
  else
    errors=$((errors+1))
  fi
done

exit $errors