#!/bin/sh
#
# Author: Andy Welter
# www.the-welters.com
# January 15, 2000
#
# Display a parent child relationship for a process or all processes
# on a system.
#
# This script uses recursive calls to itself in a bourne shell script
# which is kinda cool, but is really inefficient.
# 
# It takes advantage of the "-o" option on the PS command to put
# the PS output into a more easily parsed format and this also
# makes it more portable between Unix flavors.  Linux does not
# support this option, so unfortunately it doesn't work on Linux.
#

lookup_ancestors () {
        #
        # Find parent of current process, then recursively call this
        # script to display it's line of anscestors.
        #
        # Note that Orphan processes show pid 1 as their parent.
        #
	PID=$1
        PROC=`cat $FILE | grep "^$PID "`
	PPID=`echo "$PROC" | (read pid ppid user args;echo $ppid)`
        if [ -n "$PPID" ]; then
                if [ $PID -ne 0 ]; then
                        $0 -p $PPID
                fi
        fi
}
 
lookup_descendents () {
        #
        # Find list of children of the current process, and recursively
        # call this script for each of the children found to display
        # their children.
        cat $FILE | grep " $1 " |  \
        while read PID PPID USER ARGS; do
		if [ "$PID" != "$PPID" ]; then
                	$0 -c $PID "$indent"
		fi
        done
        }
 
display_process () {
        #
        # display the ps info of the indicated process. 
	# (can be used for parents or children)
        # $1 is the pid to display
        # $indent is the amount of indentation to display before the process
        #
        cat $FILE | grep "^$1 " | while read PID PPID USER ARGS; do
        echo "$indent$USER	$PID	$PPID	$ARGS"
	done
}
 
 
step="  "

PS="ps -ea -o pid -o ppid -o user -o args"
 
if [ "$1" = "-p" ]; then
        #
        # look up parent pid then display the current process.  
        # anscestors will be in oldest to newest order.
        #
        # don't bother indenting for parents.
        #indent="$3"
        lookup_ancestors $2
        #indent="$indent$step"
        display_process $2 
elif [ "$1" = "-c" ]; then
        #
        # lookup child pid
        #
        indent=$3
        display_process $2
        indent="$indent$step"
        lookup_descendents $2
else
	if [ "$1" = "" ]; then
		START=0
	else
		START=$1
	fi
        #
        # This is the initial call to the script.  
	# Display ancestors and descendents #
	#
        echo
        echo "================="
        echo "= Looking up information for process $START"
        echo "================="
        # Get the output to ps and normalize it's output
        FILE=/tmp/pstree.$$
        export FILE
        indent=""
        $PS | tail +2 | sed 's/^ *//g' > $FILE
        display_process $START
        #
        echo
        echo "================="
        echo "= Ancestors of process $START"
        echo "================="
        lookup_ancestors $START
        #
        echo
        echo "================="
        echo "= Descendents of process $START"
        echo "================="
        lookup_descendents $START
 
        /bin/rm $FILE
fi