#!/bin/sh

# changeUID.sh
# 
#
# Created by Eddie Kelley on 2/27/07.
# Copyright 2007 Kelley Computing. All rights reserved.
#
# This script will attempt to change a user's UID (UniqueID) to a provided UID
#

clear

# get_user_name function - this prompts for the username
get_user_name() {
	echo "Please enter short name of user who's UID you wish to modify:"
	read USERNAME

	echo "You have entered: $USERNAME - is this correct? (y/n)"
	read VERIFY_USERNAME

	if [ "$VERIFY_USERNAME" != "y" ]; then
		get_user_name
	else
		VERIFY_USER_EXISTS=`dscl . -search /users name $USERNAME | grep -w $USERNAME | wc -l`
		if [ $(($VERIFY_USER_EXISTS)) -eq 1 ]; then
			OLD_UID=`dscl . -read /users/$USERNAME UniqueID | sed -e s/UniqueID..//`
			get_new_UID
		else
			echo "Error: $USERNAME does not exist"
			get_user_name
		fi
	fi
}

# get_new_UID function - after getting the user's shortname, prompt for a new UID
get_new_UID() {
	echo "Please enter the new UID for user: $USERNAME (Current UID: $OLD_UID)"
	read NEW_UID

	echo "You have entered: $NEW_UID - is this correct? (y/n)"
	read VERIFY_UID
	if [ "$VERIFY_UID" != "y" ]; then
			get_new_UID
		else
			VERIFY_UNIQUE_UID=`dscl . -search /users UniqueID $NEW_UID | grep -w $NEW_UID | wc -l`
			if [ $(($VERIFY_UNIQUE_UID)) -gt 0 ]; then
				echo "UID: $NEW_UID already exists!"
				get_new_UID
			else
				VERIFY_GID_EXISTS=`dscl . -search /groups name $USERNAME | grep -w $USERNAME | wc -l`
				if [ $((VERIFY_GID_EXISTS)) -eq 1 ]; then
					echo "A group with the name:$USERNAME was found."
					echo "Would you like to change its GID? (y/n)"
					read CHANGE_GID
				fi
				change_UID
			fi
		fi
}

repair_permissions() {

	# change ownership (chown) of the user's home directory to match the new UID
	echo "Fixing ownership for home directory at: /Users/$USERNAME..."
	if [ "$CHANGE_GID" = "y" ]; then
		`sudo chown -R $NEW_UID:$NEW_UID /Users/$USERNAME`
	else
		`sudo chown -R $NEW_UID /Users/$USERNAME`
	fi
	
	# find all files owned by this user (in /Applications, and /Library), and change their ownership to the new values
	echo "Finding files located in /Applications and /Library to repair permissions on (this may take a while)..."
	if [ "$CHANGE_GID" = "y" ]; then
		`sudo find /.Trashes /Applications /Library -group $OLD_UID -exec chgrp $NEW_UID {} \;`
	fi
	`sudo find /.Trashes /Applications /Library -user $OLD_UID -exec chown $NEW_UID {} \;`
	
	# change the name of a couple files that have the old UID in their name
	`sudo mv /.Trashes/$OLD_UID /.Trashes/$NEW_UID`
}

# change_UID function - this does the actual work
change_UID() {
	echo "Are you sure that you want to change the UID for user: $USERNAME to: $NEW_UID ? (y/n)"
	read VERIFY_START
	if [ "$VERIFY_START" != "y" ]; then
		echo "User cancelled operation"
		exit 0;
	else
		
		
		# change the entry for PrimaryGroupID to the new GID for selected user's group
		if [ "$CHANGE_GID" = "y" ]; then
		echo "Updating PrimaryGroupID at path: /users/$USERNAME using dscl..."
			`sudo dscl . -create /groups/$USERNAME PrimaryGroupID $NEW_UID`
			VERIFY_GID_CHANGE=`sudo dscl . -read /groups/$USERNAME PrimaryGroupID | sed -e s/PrimaryGroupID..//`
			if [ "$VERIFY_GID_CHANGE" = "$NEW_UID" ]; then
				echo "The GID for group: $USERNAME was changed to: $NEW_UID"
			else
				echo "There was an error changing the GID for group: $USERNAME"
			fi
		fi
		
		# change the entry for gid to the new GID for selected user
		if [ "$CHANGE_GID" = "y" ]; then
			#if the gid of selected user matches the old uid, change it to the new one
			if [ "`sudo dscl . -read /users/$USERNAME gid | sed -e s/gid..//`" = "$OLD_UID" ]; then
				echo "Updating gid at path: /users/$USERNAME using dscl..."
				`sudo dscl . -create /users/$USERNAME gid $NEW_UID`
				VERIFY_GID_CHANGE=`sudo dscl . -read /users/$USERNAME gid | sed -e s/gid..//`
				if [ "$VERIFY_GID_CHANGE" = "$NEW_UID" ]; then
					echo "The GID for user: $USERNAME was changed to: $NEW_UID"
				else
					echo "There was an error changing the GID for user: $USERNAME"
				fi
			fi
		fi
		
		# repair file permissions for other files owned by this user
		repair_permissions
		
		# change the entry for UniqueID to the new UID for selected user
		echo "Updating UniqueID at path: /users/$USERNAME using dscl..."
		`sudo dscl . -create /users/$USERNAME UniqueID $NEW_UID`
		VERIFY_UID_CHANGE=`dscl . -read /users/$USERNAME UniqueID | sed -e s/UniqueID..//`
		if [ "$VERIFY_UID_CHANGE" = "$NEW_UID" ]; then
			echo "The UID for user: $USERNAME was changed from: $OLD_UID to: $NEW_UID"
		else
			echo "There was an error changing the UID for user: $USERNAME"
		fi
		
		# We have to reboot the computer because loginwindow gets confused
		echo "You should now restart the computer."
	fi
}

# main function - just call our get_user_name function to start the script
main() {
	echo "changeUID"
	echo ""
	echo "This script will allow you to change a user's UniqueID (UID)"
	echo "Press Control-C at any time to abort"
	echo ""
	get_user_name
}

main