TweetFollow Us on Twitter

MacEnterprise: Scripting opportunities for System Administrators, part 2

Volume Number: 25
Issue Number: 07
Column Tag: MacEnterprise

MacEnterprise: Scripting opportunities for System Administrators, part 2

Running administrative scripts at login and logout, and more

By Greg Neagle,


In an earlier issue of MacTech, we started a look at scripting opportunities for systems administrators. We talked about why you might want to run a script, when it's possible and advisable to run scripts for certain tasks, and began to look at exactly how you get your scripts to run at the right time.

Previously, we discussed running scripts at startup and on a repeating schedule. This month, we'll look at running scripts as part of the login and logout process, both with root privileges, and as the user logging in. We'll also consider scripts that should run only once, either at startup or login. Finally, we'll look at some methods to simplify implementing additional scripts once you have a few working.

Login/Logout hooks

A very common administrative need is to run a script (or scripts) when a user logs in or when a user logs out. One possible reason to do this is that you need to make a change to the user's environment: maybe you need to redirect a network user's caches to the local disk before they complete their login, or you need to do some cleanup on logout.

If you need to run a script at each user login, and the script must have superuser (root) privileges, you should consider implementing a login hook. A login hook is a script that runs as part of the login process. It runs after the user's home directory has been mounted (if it's a network user or one whose home directory has been protected with FileVault). It runs as root, but is passed the name of the user who is logging in.

To set up a login hook, make sure your script is executable:

sudo chmod 755 /path/to/script

Then set the loginhook:

sudo defaults write LoginHook /path/to/script

Log out and back in, and the hook should run. Logout hooks are set up similarly:

sudo defaults write LogoutHook /path/to/script

Here's an example of a script that could be used as a logout hook. On logout, it randomly selects a picture to use as the desktop picture/background behind the loginwindow.

#!/usr/bin/perl -w
use strict;
my $loginwindowprefs = "/Library/Preferences/";
my $picdir = "/Library/Desktop Pictures/Nature";
if ( -d "$picdir") {
   my @list = split("\n",`ls -1 "$picdir"`);
   my @pictures = ();
   for my $item (@list) {
      if (-f "$picdir/$item") {
         push @pictures, "$picdir/$item";
   if (scalar(@pictures)) {
      my $currentpicture = `/usr/bin/defaults read $loginwindowprefs DesktopPicture`;
      if ($currentpicture) { chomp($currentpicture) };
      my $randompicture = $currentpicture;
      while ($randompicture eq $currentpicture) {
         my $randomindex = int(rand(scalar(@pictures)));
         $randompicture = $pictures[$randomindex];
      my $result = `/usr/bin/defaults write $loginwindowprefs DesktopPicture "$randompicture"`;

Figure 1. MCX login scripts

Each time a user logs out, the picture behind the loginwindow is changed. Since this script runs during logout, but before the loginwindow is displayed, you should see a new picture at each logout.

Apple's Knowledge Base article on setting up a login hook is here:

MCX login scripts

There is another way to specify a specific script to run at login or logout, and that is using MCX via Workgroup Manager (Figue 1, above).

Using MCX to manage login scripts requires very specific client settings and can be tricky to get right. Make sure to read the relevant help information, accessible by clicking the purple question mark in Workgroup Manager.

Other login options

Login hooks run as the root user. There are tasks that require running as the user logging in. For these, you have a few options:

Use a login hook, but within the hook, act as the user with the su command. This can be tricky to get right.

Implement it as a launchd LaunchAgent.

Write your script as a launchable application and add it to the login items.


LaunchAgents had some pretty serious shortcomings in Tiger, but in Leopard, they are pretty useful.

A LaunchAgent is started when a user logs in, and runs as that user. As the system administrator, you should put LaunchAgent plists in /Library/LaunchAgents. /System/Library/LaunchAgents is reserved for use by Apple, and ~/Library/LaunchAgents is for the user's personal use.

Let's say you wanted to run a script at user login that would launch a setup assistant-type application - a LaunchAgent would be a good fit for this. Here's an example plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "">
<plist version="1.0">

This LaunchAgent plist has a unique label, which is simply a name for the task. A new key introduced in 10.5 Leopard is LimitLoadToSessionType, and here it is set to Aqua. This tells launchd to load the job only when there is a GUI login - if the user were to login via SSH, for example, the job would not run. This makes sense for this, as we wouldn't want our GUI setup assistant application to run if the user wasn't logging into the GUI console. If you had a job that made sense to run only for a non-GUI login, you would set the value of LimitLoadToSessionType to StandardIO. Finally, the RunAtLoad key is set to true to tell launchd to run the script immediately when loading the job after login.

For more information about LaunchAgents and their options, see this Apple Technical Note:

Last time I promised that I'd cover scripts that should run only once. A classic case is a script that launches a setup assistant. You might want it to launch the assistant the first time a user logs in, but you probably don't want it to launch every time the user logs in. Here's how you might handle this:

#run the Setup Assistant if it's never run before
$homedir = $ENV{'HOME'};
$checkFile = "$homedir/";
unless (-f "$checkFile") {
   `touch $checkFile`;
   `open "/Applications/Utilities/My Org Setup"`;

Here's what's happening. We define a filename - "". We start the name with a period so it is invisible in the Finder. The script checks for the existence of the file in the root of the current user's home directory. If it's not present, the script creates the file and opens the Setup Assistant. The next time the script runs for this user, the file will exist, and the script will exit without opening the Setup Assistant.

You can use this same basic technique for any script you want to run just once - the script actually runs at each startup/login/etc, but exits without doing anything if a certain file exists. In my opinion, this is a better approach than a script that removes itself after it runs because you can easily re-run the script in the future simply by removing its "flag" file.

Login items

There is another type of item that runs at user login. It's usually referred to as a login item, though an earlier version of Mac OS X confusingly called these "startup items". Users can add their own login items, either from the Accounts pane of the System Preferences application, or by right-clicking or control-clicking on an item in the Dock and choosing Open at Login from the contextual menu that appears.

Figure 2. Setting an item to open at login

What a system administrator needs, though, is a way to specify that certain items open for all users of a given machine. There are two ways to do this. The first, if you are using MCX, is to add the items to the managed login preferences using Workgroup Manager. The second is to add the items to the file at /Library/Preferences/loginwindow.plist:

> defaults read /Library/Preferences/loginwindow AutoLaunchedApplicationDictionary
        Hide = 1;
        Path = "/Library/Management/";

Applications added here are launched for all users of a given machine at login, in addition to whatever items a user may have added to their own list of login items. Note that the name of the key is AutoLaunchedApplicationDictionary - you have to add applications here, and not scripts - even if they are set as executable. In order to use this mechanism to run scripts, you need to either wrap your script into an application bundle, or write an app whose purpose is to run your scripts. Fortunately, I've done that work for you. A link to such an application can be found in the next section of this article.

Running multiple scripts

A major problem with login/logout hooks is that there is support for only a single login/logout script. This can be a problem if you need to implement more than one script. A solution to this problem is to implement master login/logout hooks, which in turn run additional scripts within a given directory. Here's a sample master login hook:

# Master login hook script
# runs each script found in the login hooks directory
if [ -d ${LOGINHOOKSDIR} ]; then
    for script in ${LOGINHOOKSDIR}/* ; do
        if [ -s ${script} -a -x ${script} ]; then
            # log this run
            logger -s -t LoginHook -p Executing ${script}... 1>&2
            # run the item.
            ${script} $*
            # if there was an error, log it
            if [ $rc -ne 0 ]; then
                logger -s -t LoginHook -p ${script} failed with return code ${rc} 1>&2
                exit $rc
exit 0

This master hook loops through all the items in the /etc/hooks/login directory, checks to see if each item is non-zero-length and executable, and if so, writes a message to the system log announcing it's running the item, and then runs the item, passing along any command-line parameters that were sent to the master hook. A similar script could be used to run multiple logout hooks.

In fact, this technique is useful in other scripting situations. If you create a launchd plist to run a specific script at startup, and later you want to run another script as well, you'd have to create another launchd plist for the second script. This quickly gets tedious and error-prone. If, instead, you created a script like the master loginhook that ran all the scripts in a certain directory, and created a launchd plist to run that script, then to run additional scripts, you'd only have to put them in the special directory. This enables you to do the hard work once and then add or subtract scripts as needed.

Another variation of this technique can be used to run scripts at login as the user who is logging in. You can get details on doing this at the site:

Conclusion, and More info

That concludes our look at scripting opportunities. You should now have a better idea how you can get your scripts to run at the proper time and in the proper context. Below, I've listed a few more places to get more info on some of the topics we've discussed. Good luck!

More options for running code at login, and a discussion of the pros and cons of each:

launchd, LaunchDaemons, and LaunchAgents:

Login items, login/logout hooks, and LaunchAgents:

Greg Neagle is a member of the steering committee of the Mac OS X Enterprise Project ( and is a senior systems engineer at a large animation studio. Greg has been working with the Mac since 1984, and with OS X since its release. He can be reached at


Community Search:
MacTech Search:

Software Updates via MacUpdate

Google Chrome 54.0.2840.71 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
HoudahSpot 4.2.6 - Advanced file-search...
HoudahSpot is a powerful file search tool. Use HoudahSpot to locate hard-to-find files and keep frequently used files within reach. HoudahSpot will immediately feel familiar. It works just the way... Read more
Yummy FTP Pro 1.11.11 - $29.99
Yummy FTP Pro is an advanced Mac file transfer app which provides a full-featured professional toolkit combined with blazing speeds and impeccable reliability, so whether you want to transfer a few... Read more
Shimo - VPN client – for everyon...
Shimo is the most versatile VPN client for OS X and it enables really everybody to master secure network. It supports more protocols than any other VPN application out there! CiscoVPN, AnyConnect,... Read more
Dash 3.4.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
AirRadar 3.1.9 - $9.95
With AirRadar, scanning for wireless networks is now easier and more personalized! It allows you to scan for open networks and tag them as favourites or filter them out. View detailed network... Read more
Printopia 2.1.22 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
SteerMouse 5.0 - Powerful third-party mo...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
Alarm Clock Pro 10.2.5 - $19.95
Alarm Clock Pro isn't just an ordinary alarm clock. Use it to wake you up in the morning, send and compose e-mails, remind you of appointments, randomize the iTunes selection, control an internet... Read more
Cocktail 10.1 - General maintenance and...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more

Latest Forum Discussions

See All

Game of Dice is now available on Faceboo...
After celebrating its anniversary in style with a brand new update, there’s even more excitement in store for Game of Dice has after just being launched on Facebook Gameroom. A relatively new platform, Facebook Gameroom has been designed for PC... | Read more »
4 addictive clicker games like Best Fien...
Clickers are passive games that take advantage of basic human psychology to suck you in, and they're totally unashamed of that. As long as you're aware that this game has been created to take hold of your brain and leave you perfectly content to... | Read more »
Smile Inc. Guide: How not to die on the...
As if Mondays weren't bad enough, at Smile Inc. you have to deal with giant killer donuts, massive hungry staplers, and blasting zones. It's not exactly a happy, thriving work environment. In fact, you'll be lucky to survive the nine to five.... | Read more »
Oh...Sir! The Insult Simulator (Games)
Oh...Sir! The Insult Simulator 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
WitchSpring2 (Games)
WitchSpring2 1.27 Device: iOS Universal Category: Games Price: $3.99, Version: 1.27 (iTunes) Description: This is the story of Luna, the Moonlight Witch as she sets out into the world. This is a sequel to Witch Spring. Witch Spring 2... | Read more »
4 popular apps getting a Halloween makeo...
'Tis the season for all things spooky. So much, so, in fact, that even apps are getting into the spirt of things, dressing up in costume and spreading jack o' lanterns all about the place. These updates bring frightening new character skins, scary... | Read more »
Pokémon GO celebrates Halloween with can...
The folks behind Pokémon GO have some exciting things planned for their Halloween celebration, the first in-game event since it launched back in July. Starting October 26 and ending on November 1, trainers will be running into large numbers of... | Read more »
Best Fiends Forever Guide: How to collec...
The fiendship in Seriously's hit Best Fiends has been upgraded this time around in Best Fiends Forever. It’s a fast-paced clicker with lots of color and style--kind of reminiscent of a ‘90s animal mascot game like Crash Bandicoot. The game... | Read more »
5 apps for the budding mixologist
Creating your own cocktails is something of an art form, requiring a knack for unique tastes and devising interesting combinations. It's easy to get started right in your own kitchen, though, even if you're a complete beginner. Try using one of... | Read more »
5 mobile strategy games to try when you...
Strategy enthusiasts everywhere are celebrating the release of Civilization VI this week, and so far everyone seems pretty satisfied with the first full release in the series since 2010. The series has always been about ultra-addictive gameplay... | Read more »

Price Scanner via

13-inch 2.5GHz MacBook Pro (Apple refurbished...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros... Read more
Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
64GB Apple TV on sale for $159, save $40
Best Buy has the 64GB Apple TV on sale for $40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store price may... Read more
EyeQue Introduces iOS And Android Based Advan...
Affordable vision technologies developers EyeQue have announced what they claim to be the world’s most advanced intelligent vision solution, pitched as enabling anyone, anywhere to easily and... Read more
Smartwatch Market Tanks, Declining 51.6% in 2...
The worldwide smartwatch market experienced a round of growing pains in the third quarter of 2016 (3Q16), resulting in a year-over-year decline in shipment volumes. According to data from the... Read more
CAZE announces Ultra Thin Glass Screen Protec...
Hong Kong based CAZE has announced its first ultra thin glass screen protector, the Glazz Pro for iPhone 7/7 Plus. Glazz Pro is made from chemically reinforced glass with an anti-fingerprint... Read more
11-inch MacBook Airs on sale for up to $120 o...
Newegg has 11″ MacBook Airs on sale for up to $120 off MSRP. Shipping is free: - 11″ 1.6GHz/128GB MacBook Air: $799.99 $100 off MSRP - 11″ 1.6GHz/256GB MacBook Air: $979 $120 off MSRP Read more
Up to $300 off Macs, $20 off iPads with Apple...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Apple’s Thursday “Hello Again” Event A Largel...
KGI Securities analyst Ming-Chi Kuo, who has a strong record of Apple hardware prediction accuracy, forecasts in a new note to investors released late last week that a long-overdue redo of the... Read more
12-inch Retina MacBooks on sale for $100 off...
Amazon has 2016 12″ Apple Retina MacBooks on sale for $100 off MSRP. Shipping is free: - 12″ 1.1GHz Silver Retina MacBook: $1199.99 $100 off MSRP - 12″ 1.1GHz Gold Retina MacBook: $1199.99 $100 off... Read more

Jobs Board

Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 52812872 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Solutions Read more
Lead *Apple* Solutions Consultant - Apple (...
# Lead Apple Solutions Consultant Job Number: 52812906 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Lead ASC is an Read more
*Apple* Retail - Multiple Positions- Towson,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.