Shell scripting in macOS – Part 2: Managing information

This article is a continuation of the previous article. We will be taking the previous script and using it to build on the concepts we will learning in this article.

Using Variables to store information

First up we will look at variable. Variables are containers that can hold information. The biggest advantage of this is the fact that we can use information in our tasks simply by reusing the variable it is stored in. This means if there is any change at a later date, then we only have to change the value in the variable. 

So, in the future, if there is a need to modify the information, we only have a single point of change to make. This greatly aids  in the ease of maintenance of the code.

It also makes the script more readable.

NOTE: The value of a variable can be changed at a later point of time within the script. 

Creating variables is very easy. You simply declare a name and assign it a value using the = operator. For example, if we are going to be using the path to the logs folder then storing it in a variable called PATH_TO_LOGS makes sense. We would then follow it up with the = sign and follow that up with the path in quotes. 

PATH_TO_LOGS=“/Library/Logs/“

To use this variable in a command we would simple callout the name with the $ symbol prefixed before it. 

echo $PATH_TO_LOGS

The $ symbol is necessary to access the value being held by the container.

While declaring variables try to use names which explain the purpose of the variable.

Built in variables

We can see that it is very easy to define our own variables. However, we are not restricted to creating our own variables. The system provides us with predefined variables. These give us access to useful information such as:

  • Path to the current user’s home folder.
  • The shell interpreter being used.
  • The currently logged in user name. 

We can get the complete list of commands with the help of the printenv command.

printenv

How about using these variables? Well, we will use it the same way we would use our own variables. Just prefix the $ symbol before the variable name. 

echo "The path to the home folder is $HOME"

Let us update the script from the previous article.

#!/bin/zsh

echo "Running script to create folders."

TOOLS_FOLDER="Tools"
REPORTS_FOLDER="Reports"
HELP_FOLDER="Help"

TOOLS_FOLDER_CREATED=".$TOOLS_FOLDER-FolderCreated"
REPORTS_FOLDER_CREATED=".$REPORTS_FOLDER-FolderCreated"
HELP_FOLDER_CREATED=".$HELP_FOLDER-FolderCreated"

cd $HOME

echo "Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER"
mkdir $TOOLS_FOLDER
mkdir $REPORTS_FOLDER
mkdir $HELP_FOLDER

echo "Creating hidden file for $TOOLS_FOLDER folder."
cd $TOOLS_FOLDER
touch $TOOLS_FOLDER_CREATED
cd ..

echo "Creating hidden file for $REPORTS_FOLDER folder."
cd $REPORTS_FOLDER
touch $REPORTS_FOLDER_CREATED
cd ..

echo "Creating hidden file for $HELP_FOLDER folder."
cd $HELP_FOLDER
touch $HELP_FOLDER_CREATED
cd ..

echo "Task completed. Have a nice day!"

Capturing command output

Now that we have seen how variables can be created and used, then next logical step is to use them to store the outcome of a command. Why would we need to do this? Let us suppose that a command returns the path to a folder and we would like to perform multiple tasks on this folder. We can simply save the path in a variable and then use the variable across the script. 

If storing the result of the command in a variable wasn’t possible then we would have to execute the command over and over again every time we needed the result.

But before we store the outcome of the command we first need to understand how we can capture the output of a command itself. This is done with the help of command substitution. The command to be executed is placed within the $ symbol followed by parentheses.

So to store it in a variable we would just place the command we would just place this on he right hand side of the = sign. For example, if we wanted to store today’s date we would use the date command placed within the $() on the right hand side of the = sign. On the left hand side of the = sign would be the name of our variable.

TODAY=$(date)

There is an older way of doing the same thing, instead of using the $() the command would be placed within 2 back ticks.

TODAY=`date`

Writing to files

While it is useful to store information within variables there are some limitation with this. Sometimes we would like to store our data outside the script for example on some other file. The advantage with this approach is that it allows us to access the information across multiple invocations of the script. 

The way we write to a file is by redirecting the output of the command from standard output to a file. There are 2 operators that help us with this.

The redirect operator with a single angle bracket will write the contents to a file. This will replace the existing content fo the file.

echo "Hello, World!" > /Users/Shared/message.txt

The redirect operator with 2 angle brackets will also write contents to a file. But this will append or add the existing content. 

echo "Hello, World!" >> /Users/Shared/message.txt

Depending on what you want you can use one of the 2 approaches. 

Logging events taking place in the script

A log file is used to note done certain events being performed by an app, script, process, or any task. It is a very useful troubleshooting tool. This would be a nice feature to add to our script. We can log the different events that are taking place. To do this we will use the same redirect operator to write to a file.

Log files are typically stored in one of two locations in macOS:

  • ~/Library/Logs/
  • /Library/Logs

For our demo we will store it in the ~/Library/Logs/ folder. This makes sense because our script will be making changes to a user’s home folder. So ideally, the log file should also stay in the user’s home folder.

The way we will generate our log file is by redirecting the output of the echo command to our file.

echo "Hello, World!" >> ~/Library/Logs/folderCreator_log_v1-1.log

So all the echo statements we have will be modified to redirect to the log. Additionally, we will use command substitution to include the date and time in out message. Let us modify the script above to reflect these new changes.

#!/bin/zsh

echo "$(date) Running script to create folders."

TOOLS_FOLDER="Tools"
REPORTS_FOLDER="Reports"
HELP_FOLDER="Help"

TOOLS_FOLDER_CREATED=".$TOOLS_FOLDER-FolderCreated"
REPORTS_FOLDER_CREATED=".$REPORTS_FOLDER-FolderCreated"
HELP_FOLDER_CREATED=".$HELP_FOLDER-FolderCreated"

TODAY=$(date)
PATH_TO_LOG="$HOME/Library/Logs/folderCreator_log_v1-1.log"

echo "$(date) Starting" >> $PATH_TO_LOG

cd $HOME

echo "$(date) Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER" >> $PATH_TO_LOG
mkdir $TOOLS_FOLDER
mkdir $REPORTS_FOLDER
mkdir $HELP_FOLDER

echo "$(date) Creating hidden file for $TOOLS_FOLDER folder." >> $PATH_TO_LOG
cd $TOOLS_FOLDER
touch $TOOLS_FOLDER_CREATED
cd ..

echo "$(date) Creating hidden file for $REPORTS_FOLDER folder." >> $PATH_TO_LOG
cd $REPORTS_FOLDER
touch $REPORTS_FOLDER_CREATED
cd ..

echo "$(date) Creating hidden file for $HELP_FOLDER folder." >> $PATH_TO_LOG
cd $HELP_FOLDER
touch $HELP_FOLDER_CREATED
cd ..

echo "$(date) Task completed. Have a nice day!"

Passing information to a script

While storing information and capturing information within a script is useful. It is also useful to have the ability to give information to a script at the time of running the script. This allows the user of the script to have greater control over the end result or outcome. 

The information that is passed into the script is store in predefined variables known as positional variables. They are named $0, $1, $2 and onwards. Let us modify the script to use these variables.

#!/bin/zsh

echo "$(date) Running script $0 to create folders."

TOOLS_FOLDER=$1
REPORTS_FOLDER=$2
HELP_FOLDER=$3

TOOLS_FOLDER_CREATED=".$TOOLS_FOLDER-FolderCreated"
REPORTS_FOLDER_CREATED=".$REPORTS_FOLDER-FolderCreated"
HELP_FOLDER_CREATED=".$HELP_FOLDER-FolderCreated"

TODAY=$(date)
PATH_TO_LOG="$HOME/Library/Logs/folderCreator_log_v1-1.log"

echo "$(date) Starting" >> $PATH_TO_LOG

cd $HOME

echo "$(date) Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER" >> $PATH_TO_LOG
mkdir $TOOLS_FOLDER
mkdir $REPORTS_FOLDER
mkdir $HELP_FOLDER

echo "$(date) Creating hidden file for $TOOLS_FOLDER folder." >> $PATH_TO_LOG
cd $TOOLS_FOLDER
touch $TOOLS_FOLDER_CREATED
cd ..

echo "$(date) Creating hidden file for $REPORTS_FOLDER folder." >> $PATH_TO_LOG
cd $REPORTS_FOLDER
touch $REPORTS_FOLDER_CREATED
cd ..

echo "$(date) Creating hidden file for $HELP_FOLDER folder." >> $PATH_TO_LOG
cd $HELP_FOLDER
touch $HELP_FOLDER_CREATED
cd ..

echo "$(date) Task completed. Have a nice day!"

The final script should look like:

#!/bin/zsh
echo "$(date) Running script $0 to create folders."
TOOLS_FOLDER=$1
REPORTS_FOLDER=$2
HELP_FOLDER=$3
TOOLS_FOLDER_CREATED=".$TOOLS_FOLDER-FolderCreated"
REPORTS_FOLDER_CREATED=".$REPORTS_FOLDER-FolderCreated"
HELP_FOLDER_CREATED=".$HELP_FOLDER-FolderCreated"
TODAY=$(date)
PATH_TO_LOG="$HOME/Library/Logs/folderCreator_log_v1-1.log"
echo "$(date) Starting" >> $PATH_TO_LOG
cd $HOME
echo "$(date) Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER" >> $PATH_TO_LOG
mkdir $TOOLS_FOLDER
mkdir $REPORTS_FOLDER
mkdir $HELP_FOLDER
echo "$(date) Creating hidden file for $TOOLS_FOLDER folder." >> $PATH_TO_LOG
cd $TOOLS_FOLDER
touch $TOOLS_FOLDER_CREATED
cd ..
echo "$(date) Creating hidden file for $REPORTS_FOLDER folder." >> $PATH_TO_LOG
cd $REPORTS_FOLDER
touch $REPORTS_FOLDER_CREATED
cd ..
echo "$(date) Creating hidden file for $HELP_FOLDER folder." >> $PATH_TO_LOG
cd $HELP_FOLDER
touch $HELP_FOLDER_CREATED
cd ..
echo "$(date) Task completed. Have a nice day!"

Script locations

One last thing to talk about now is script locations. So far we have been placing our scripts where ever we wish and running them from there. But it may be a good idea to use a consistent location for the same. There are several candidates for this:

  • ~/Library/Scripts/
  • /Library/Scripts/

These are the more standard locations.

The only decision that needs to be made is whether it is the Library folder in the user’s home folder or the library folder located at root. This affects if the script is available only for a specific user or for all users on a computer.

There are other locations possible too. Developers often have a folder in the home folder called “Developer”. This needs to be manually created, but once created the system recognises it as the folder where files related to development are kept. You can create a scripts folder and place it in there.

Another popular location is the Application Support folder within the library folder. You can create a folder that represents items related to your scripts and then place the script in that folder. Note that these folders will have to be created by manually.

  • ~/Developer/Scripts/
  • ~/Library/Application Support/<your folder>/

These 2 locations would need to be created.

Scripts are not typically exposed to the end user. There is typically some kind of scheduling mechanism that triggers them. However, if a script is designed to be used by the end user you could even place them in:

  • /Applications/Scripts/
  • ~/Applications/Scripts/

Like the developer folder the applications folder in the home folder needs to be created. But once created the system recognises what it is intended for and gives it special privileges. The scripts folder within it will have to be created manually.

While this may not seem like a big deal. Placing your scripts in the correct location can lead to more consistent experiences, make troubleshooting easy, and also hide potential complexity.

Conclusion

The ability to store data within a script, pass data to a script or store data on an external file from within a script has several advantages. This makes the script more power and compact at the same time. It also makes the script less susceptible to errors and mistakes.

Video

Download

You can download the script from the same git repository as the previous one. The script is named folderCreator_v1-1.zsh.

Screen capture and recording in macOS

Continuing from the articles on recording macOS and iOS screens here is another handy built in tool.

Press the key combination ⇧ ⌘ 5 and it brings the screen capture/recording menu.

You can perform all the operations available from the menu here.

Of course once we start the recording then we can see the record button in the menu bar.

Once the recording is completed you can save it as a movie file.

This unified interface now offers a lot of convenient options for capturing visual content in macOS.

List of macOS Terminal commands

This article lists out different macOS terminal commands you might encounter. You can use this list as a starting point in your search for a command to perform a specific task. This list is by no means exhaustive.

Basic terminal commands are not listed here. Some of them are listed in the following Terminal command articles.
Terminal Commands – Basic
Terminal Commands – Part 2
Terminal Commands – Part 3

Many of the commands have also been used in the article I wrote some time back. You can have a look at the scripts to see some of the commands being used.

To get more information about the commands simply run the following command from within Terminal Application. For example, to view the manual page for tmutil simply type:

man tmutil

For fdesetup

man fdesetup
Here is a nice command to quickly open the man page in the Preview App.
man -t tmutil | open -f -a /System/Applications/Preview.app

Note

  • This is not a complete list of commands
  • Some commands are available through the macOS Recovery Volume only
  • Some commands required other resources such as the OS installer
  • Some commands are available with certain versions of the OS only

Please read the documentation for more details. Use the commands with care. Improper use of commands may result in loss of data or damage to the computer.

Commands


Installation

CommandDescription
startosinstallUsed to start the installation of macOS from the command line.
createinstallmediaUsed to create an external install disk.

Security

CommandDescription
fdesetupManage FileVault configuration.
securityManage keychain and security settings
spctlManage security assessment policy
csrutilConfigure System Integrity Protection (SIP) settings
resetpasswordPassword reset utility located in the Recovery Partition

File System

CommandDescription
hdiutilUsed to manipulate and manage disk images.
diskutilUsed to modify, verify, & repair local disks.

Data Management

CommandDescription
tmutilUsed to configure Time Machine settings in macOS
screencaptureTakes screenshot of the specified screen and saves the image at the specified location.
mdlsUsed to get metadata attributes for a given file
mdutilUsed to manage metadata stores that are used by Spotlight

Settings

CommandDescription
defaultsUsed to modify plist files. Typically used to update preference files.
ioregUsed to view the I/O kit registry
system_profilerUsed to generate system hardware & software reports.
plutilUsed to check syntax of property lists or covert property lists from one format to another
AssetCacheManagerUtilUsed to configure content caching settings.
openUsed to open documents from within the command line.
networksetupPerform network configuration.
systemsetupUsed to configure machine settings in System Preferences.
launchctlUsed to manage and inspect daemons, agents, & XPC Services

Applications

CommandDescription
codesignUsed to create, check, display code signatures.
pkgbuildUsed to build installer packages
productbuildBuilds a product archive
installerSystem software and package installer tool

User Account Management

CommandDescription
dsclThis is a command line Directory service utility that allows us to create, read, and manage Directory Service data.
sysadminctlUser account management
passwdChange user password
loginUsed to login to another user account.

Server & Device Management

CommandDescription
profilesUsed to install, remove, list, or manage Configuration profiles.
serveradminUsed to manage the services in macOS
mdmclientLocated in /usr/libexec/mdmclient it is used to manage interactions with the MDM.
asrApple Software restore: Used to copy volumes.

Scripting

CommandDescription
osascriptUsed to execute the given AppleScript

Share any commands you may know of in the comments window.

Disclaimer

The information Is Provided “As Is”, Without Warranty Of Any Kind, Express Or Implied, Including But Not Limited To The Warranties Of Merchantability, Fitness For A Particular Purpose And Noninfringement. In No Event Shall The Authors Or Copyright Holders Be Liable For Any Claim, Damages Or Other Liability, Whether In An Action Of Contract, Tort Or Otherwise, Arising From, Out Of Or In Connection With The information provided Or The Use Or Other Dealings In The information.

Useful scripts for macOS

Getting Started

You might find these articles useful

One of the advantages with scripts is the fact that you can easily automate many tasks. Here is an article that walks you through that process.

If you come across a situation where you want to perform a set of tasks on multiple computers then scripts come in very handy.

I will be providing the Shell Script version of the task. Feel free to make changes to the scripts as required. I will try to provide an AppleScript version of the tasks a little later.

This is not the only way to implement the scripts. There may be multiple approaches towards achieving the same result. You will have to explore and examine the correct approach.

This is not a comprehensive list. The scripts should give you some ideas and act as a useful reference when you are creating your own scripts.

I have tested these scripts on macOS Catalina 10.15

Download

You can download all the scripts from here.

Script CategoryPage Number
Settings and Accounts1
Security2
Data3
Information Collection4
File System5

Disclaimer

The Software Is Provided “As Is”, Without Warranty Of Any Kind, Express Or Implied, Including But Not Limited To The Warranties Of Merchantability, Fitness For A Particular Purpose And Noninfringement. In No Event Shall The Authors Or Copyright Holders Be Liable For Any Claim, Damages Or Other Liability, Whether In An Action Of Contract, Tort Or Otherwise, Arising From, Out Of Or In Connection With The Software Or The Use Or Other Dealings In The Software.


WARNING

Please try these scripts on a test computer. Some of the scripts do make changes to the system. Always test before using these scripts.

Creating your own Drag and Drop DMG

What are Disk Images?

Disk images are a means of archiving data. They are created using a tool called Disk Utility which is a File System Management Utility of macOS. Disk Images follow the extension ‘.dmg‘ and are only compatible with macOS.

Disk Images are a popular way of distributing applications for macOS. They provide the capability of compressing large files and make delivery over the internet very easy.

In this article we are going to look at how we can create disk images for application distribution.

Creating the DMG Folder for distribution

  1. Create a Background image. This can have any design. It’s a good idea to have arrows or other visual aids to assist others during installation.
  2. Create a new Disk Image. Open Disk Utility.
  3. Click on File > New Image > Blank Image
  4. Leave the default settings as is. Choose the size that you desire.
  5. Mount the Disk Image.
  6. Create a folder called background in the mounted volume.
  7. Save the background image in the folder we just created.
  8. Now we will hide the background folder. Switch to terminal and run the following command.

     
    cd /Volume/InstallDMG/
    mv background .background
    


    Here we are simply renaming the background folder with a ‘.’ before it. This hides the folder from the GUI.

    Now we will prepare the payload. This can be any file or folder we wish to install. For the sake of this demo I will be choosing Mozilla FireFox. In reality you would be distributing your own application.
  9. Copy the FireFox app into the mounted volume.
  10. Open “Show View Options“.
  11. Restrict the mounted volume to icon view only. Feel free to customise the other settings as you wish. This includes icon size.
  12. Drag and arrange the icons in your mounted window to match the background.
  13. Eject the disk image. 
  14. Make a duplicate copy of the image file. This can act as a reference for future images you wish to create.
  15. Now we will convert the disk image into a read only compressed disk image. This will be the one that we will use for distribution. Open Disk Utility.
  16. Click on Images > Convert
  17. Select the InstallerDMG.dmg from Desktop or wherever you had saved it.
  18. Give it a new name and convert it to compressed format.

That’s it. You now have your own drag drop window ready for distribution.

Screen and Audio recording on macOS & iOS

In this article we are going to look at how we can use the built in Application: QuickTime to record a screen or a movie. In fact, the videos that you are about to see in the article below were created using QuickTime.

A good reason to record the activity on the screen would be to create a visual step by step guide which can be distributed to employees in the organisation. For example, you can create a video to show employees how they can sign into their company’s email account and access it from their iPhone or Mac.

Recording your Mac’s screen

Follow the steps given below to record your Mac’s screen:

  1. Open QuickTime Player
  2. Click on File > New Screen RecordingScreen Shot 2018-01-24 at 4.46.22 PM
  3. You should see the window popping up.
  4. From the drop down next to the Record button select the audio input & whether mouse clicks should be shown.Screen Shot 2018-01-24 at 4.47.29 PM
  5. Click on the Record Button. You should see a dialog asking you whether you want to record a small area or a full screen.Screen Shot 2018-01-24 at 4.47.52 PM
  6. The recording starts once the stop button in the menu bar becomes dark.
  7. Click on the stop button to stop the recording.
    Screen Shot 2018-01-24 at 4.57.49 PM
  8. Save the file that was created.

Recording your iPhone/iPad Screen

(Mirroring your iPhone Screen on the Projector)

The process of recording the iPhone/iPad screen is quite similar to recording your computer’s screen. The key thing to remember is to connect your iPhone/iPad to the Mac with the lightning cable.

Follow the steps given below to record your iPhone/iPad screen:

  1. Open QuickTime Player
  2. Click on File > New Movie Recording
  3. You should see the window popping up.
  4. From the drop down next to the Record button select the audio input & whether mouse clicks should be shown. The difference now is the fact that you get an extra option to choose the source.

Recording a Movie

Follow the steps given below to record a Movie on your Mac:

  1. Open QuickTime Player
  2. Click on File > New Movie RecordingScreen Shot 2018-01-29 at 4.11.38 PM
  3. You should see the window popping up.
  4. From the drop down next to the Record button select the audio input. You can also select your camera source from here.
    Screen Shot 2018-01-29 at 4.21.41 PM
  5. Click record to start recording & click on the stop button to stop recording.

Recording Audio

Follow the steps given below to record an Audio on your Mac:

  1. Open QuickTime Player
  2. Click on File > New Audio RecordingScreen Shot 2018-01-29 at 4.11.38 PM copy
  3. You should see the window popping up.
  4. From the drop down next to the Record button select the audio input.
  5. Click record to start recording and stop to stop recording.

Here is a quick video on how to perform the different tasks that we have seen above.