Shell scripting in macOS – Part 5: Loops

December 19, 2022December 19, 2022 / Arun Patwardhan / 2 Comments

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.

Loops

Often times we will come across a situation where we want to perform a task repeatedly with different pieces of data.

For example, here is a snippet of our shell script:

if [[ -d $TOOLS_FOLDER ]]; then
	echo "$(date) Not creating $TOOLS_FOLDER as it already exists." >> $PATH_TO_LOG
else
	echo "$(date) Creating $TOOLS_FOLDER" >> $PATH_TO_LOG
	mkdir $TOOLS_FOLDER
fi

if [[ -d $REPORTS_FOLDER ]]; then
	echo "$(date) Not creating $REPORTS_FOLDER as it already exists." >> $PATH_TO_LOG
else
	echo "$(date) Creating $REPORTS_FOLDER" >> $PATH_TO_LOG
	mkdir $REPORTS_FOLDER
fi

if [[ -d $HELP_FOLDER ]]; then
	echo "$(date) Not creating $HELP_FOLDER as it already exists." >> $PATH_TO_LOG
else
	echo "$(date) Creating $HELP_FOLDER" >> $PATH_TO_LOG
	mkdir $HELP_FOLDER
fi

You can see that we are performing the same task repeatedly. Only the name of the folder is changing. This is the kind of situation that we will commonly encounter. Loops can help us make the script a little more efficient.

Handling loops

We are going to look at 2 solutions for handling loops:

For loop
While loop

For loops

A for loop works on a collection of data. It steps through the collection in the sequence in which it is present and picks one item from it at a time. The loop then performs the tasks specified in it using the item collected. Once finished it proceeds to pick up the next item. This is done till all the items in the collection are used.

Here is an example of a simple for loop. It contains 4 pieces of data in its collection: “Applications”, “Documents”, “Downloads”, & “Library”.

#!/bin/bash

for folder in Applications Documents Downloads Library
do	
	echo "The folder is $folder"
done

The output would be:

The folder is Applications
The folder is Documents
The folder is Downloads
The folder is Library

The collection could be data coming from somewhere else; such as the output of a command.

#!/bin/bash

for details in $(ls)
do
	echo "-> $details"
done

The output would be:

-> Desktop
-> Documents
-> Downloads
-> Library
-> Movies
-> Music
-> Pictures
-> Public

While loops

A while loop also performs tasks repeatedly. However it does this till a certain condition is satisfied. So we could use the test operations we learnt in an earlier article to achieve the check.

#!/bin/bash

while [[ ! -f /Users/Shared/exit.txt ]]; do
	echo "File not found"
done

echo "Found"

The script is checking to see if the file at the given path exists. If the file doesn’t exist then it prints out a message and performs the check again.

This will be done till the file is found.

NOTE: If you are testing the above code then you will need to create the file manually. You can do that by executing the following command in terminal:

touch /Users/Shared/exit.txt

Example

Let us go ahead and update our script.

First we will remove the variables that store the names for the hidden files.
Next we will remove the code for creating the folders. This will be replaced by a single block of code inside a for loop. Just remove the code for the reports folder and the help folder. We will use the code for the tools folder inside the for loop.
Right below the line where we echo out the statement that we are creating the folder, add the code for the for loop. Move the remaining folder creation logic inside it and rename the variable.

for item in $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER; do
	if [[ -d $item ]]; then
		echo "$(date) Not creating $item as it already exists." >> $PATH_TO_LOG
	else
		echo "$(date) Creating $item" >> $PATH_TO_LOG
		mkdir $item
	fi

done

Next, remove the code to create the hidden file. As before, only remove the code for creating the hidden file for the reports and help folders.
Copy the remaining lines of code into the for loop. Place it right after the fi statement.

for item in $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER; do
	if [[ -d $item ]]; then
		echo "$(date) Not creating $item as it already exists." >> $PATH_TO_LOG
	else
		echo "$(date) Creating $item" >> $PATH_TO_LOG
		mkdir $item
	fi
	
	#6. Create the task completion file inside each folder.
	echo "$(date) Creating hidden file for $item folder." >> $PATH_TO_LOG
	cd $item
	#7. Generate the file names based on the folder names.
	touch ".$item-FolderCreated"
	cd ..
done

Your final script should look like this:

#!/bin/zsh

#-------------------------------------------------------------------------------------------------
#NAME: Folder creator
#AUTHOR: Arun Patwardhan
#CONTACT: arun@amaranthine.co.in
#DATE: 10th August 2021
#WEBSITE: https://github.com/AmaranthineTech/ShellScripts
#-------------------------------------------------------------------------------------------------

#LEGAL 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.
#-------------------------------------------------------------------------------------------------

#LICENSE/TERMS AND CONDITIONS --------------------------------------------------------------------
#MIT License

#Copyright (c) Amaranthine 2021.

#Permission is hereby granted, free of charge, to any person obtaining a copy
#of this software and associated documentation files (the "Software"), to deal
#in the Software without restriction, including without limitation the rights
#to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#copies of the Software, and to permit persons to whom the Software is
#furnished to do so, subject to the following conditions:

#The above copyright notice and this permission notice shall be included in all
#copies or substantial portions of the Software.
#-------------------------------------------------------------------------------------------------

#ABOUT -------------------------------------------------------------------------------------------
# fileCreator.zsh
# 1.4
#-------------------------------------------------------------------------------------------------

#DESCRIPTION -------------------------------------------------------------------------------------
# - THis script is intended for creating the custom folders that are required on all corporate computers.
# - Run this script on a new computer or a computer being reassigned to another employee.
# - This script can run on all computers.
#-------------------------------------------------------------------------------------------------

#USAGE -------------------------------------------------------------------------------------------
# - To create folders with default names run the command: ./folderCreator.zsh
# - To define your own folder names: ./folderCreator.zsh <folder1> <folder2> <folder3>
# - Available options : Only the help option is available
# - Getting help : Use the -h or the -help options to get more information. Or you can use the man command to view the man page.
#-------------------------------------------------------------------------------------------------

#WARNING/CAUTION ---------------------------------------------------------------------------------
#******************************************************************************************************************
#******************************************************************************************************************
#******************************************************************************************************************
#******************************************************************************************************************
# This script doesn't perform any validation of the folder names being passed in by the user.
# If the script does not see the -h or the -help options then it will assume that the data being passed in is the name of the folder.
# The user of the script must ensure that the desired folder names are passed in.
#******************************************************************************************************************
#******************************************************************************************************************
#******************************************************************************************************************
#******************************************************************************************************************
#-------------------------------------------------------------------------------------------------

#INSTALLATION ------------------------------------------------------------------------------------
# Instructions for placing the script in the correct place are listed here.
# Location: /Library/Scripts/
# Permissions: rwx r-x r-x
#-------------------------------------------------------------------------------------------------

#REQUIREMENTS ------------------------------------------------------------------------------------
# Shell: /bin/zsh
# OS: macOS Big Sur 11.4 or later
# Dependencies: None
#-------------------------------------------------------------------------------------------------

#HELP/SUPPORT ------------------------------------------------------------------------------------
# You can get help by running the following commands.
# ./folderCreator.zsh -h
# ./folderCreator.zsh -help
# OR
# man folderCreator.zsh
# You can also view the log file for the same at: ~/Library/Logs/folderCreator_log_v1-4.log
#-------------------------------------------------------------------------------------------------

#HISTORY -----------------------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------
# Version 1.0: Basic script which creates the folders
# Version 1.1: Gives user the ability to specify the folder names at run time.
# Version 1.2: Adds safety checks to the scripts
# Version 1.3: Includes documentation as well as ability to get help.
# Version 1.4: Includes optimisation using for loop
#-------------------------------------------------------------------------------------------------

#-------------------------------------------------------------------------------------------------
# ------------------------------ SCRIPT STARTS HERE ----------------------------------------------
#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------

#These are the default values used for the folder names incase the user doesn't provide any.
TOOLS_FOLDER="Tools"
REPORTS_FOLDER="Reports"
HELP_FOLDER="Help"

#Script version number
VERSION_NUMBER="1.4"

#Command name
COMMAND_NAME="folderCreator.zsh"

#1. Check to see if the user is asking for help. In which case we will have to provide information about the command.
if [[ $1 == "-h" ]] || [[ $1 == "-help" ]]; then
echo "ABOUT
-----
fileCreator_v1-4.zsh
Version $VERSION_NUMBER

NAME
----
$COMMAND_NAME — Folder creation utility SYNOPSIS
$COMMAND_NAME folder names [ verbs ]

DESCRIPTION
-----------
$COMMAND_NAME creates 3 folders in the home folder. In case the folder names are not provided then the command will create folders with default names 'Tools', 'Reports', \"Help\".

There is also the option of getting help via the help verb.
- This script is intended for creating the custom folders that are required on all corporate computers.
- Run this script on a new computer or a computer being reassigned to another employee.
- This script can run on all computers.

VERBS
-----
[ −h −help] Both the options are used to invoke the help documentation.
[ −v −version] Both the options are used to get the version number of the folderCreator command.

REQUIREMENTS
------------
The following are the minimum requirements to get the script running.
Shell:\t\t zsh
OS:\t\t macOS Big Sur 11.4 or later
Dependencies:\t None

INSTALLATION
------------
$COMMAND_NAME can be installed anywhere you wish. However, there are certain locations that are recommended.
Location:\t /Library/Scripts/
Permissions: \t rwxr-xr-x

USAGE
-----
$COMMAND_NAME folder1 folder2 folder3
Will create folders with your own names.

$COMMAND_NAME -h OR $COMMAND_NAME -help
Will invoke the help utility.

$COMMAND_NAME -v OR $COMMAND_NAME -version
will print the version number in stdout.

EXAMPLES
--------
$COMMAND_NAME Resources Results Assistant
This will create 3 folders Resources , Results , Assistant , in the user’s home folder.

$COMMAND_NAME
This will create 3 folders with the default names

$COMMAND_NAME Apps
This will use the Apps name for the first folder but the default names for the last 2 folders.

DIAGNOSTICS
-----------
The script produces a log file called ~/Library/Logs/folderCreator_log_v1-x.log
This file is typically located in the user’s home folder log folder. The x represents the version number of $COMMAND_NAME
You can view the logs for each respective version.

EXIT STATUS
-----------
In most situations, $COMMAND_NAME exits 0 on success"
exit 0
fi

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

#2. Check to see if the version number is
if [[ $1 == "-version" ]] || [[ $1 == "-v" ]]; then
echo "Version: $VERSION_NUMBER"
exit 0
fi

#3. The following if statements check to see if the script is receiving any arguments. It then picks those arguments and assigns them to the respective variables for use in the script.
if [[ $1 != "" ]]; then
TOOLS_FOLDER=$1
fi

if [[ $2 != "" ]]; then
REPORTS_FOLDER=$2
fi

if [[ $3 != "" ]]; then
HELP_FOLDER=$3
fi

TODAY=$(date)
PATH_TO_LOG="$HOME/Library/Logs/folderCreator_log_v1-4.log"

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

#4. Go to the home folder.
cd $HOME

#5. Check to see if each of the folders exists. If it exists then do not create it. Else create the folder.
echo "$(date) Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER" >> $PATH_TO_LOG

for item in $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER; do
if [[ -d $item ]]; then
echo "$(date) Not creating $item as it already exists." >> $PATH_TO_LOG
else
echo "$(date) Creating $item" >> $PATH_TO_LOG
mkdir $item
fi

#6. Create the task completion file inside each folder.
echo "$(date) Creating hidden file for $item folder." >> $PATH_TO_LOG
cd $item
#7. Generate the file names based on the folder names.
touch ".$item-FolderCreated"
cd ..
done

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

#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------
# ------------------------------ END OF SCRIPT --------------------------------------------------

Video

Download

You can download the completed script from here.

Shell scripting in macOS – Part 7: Miscellaneous

May 7, 2022January 20, 2023 / Arun Patwardhan / 2 Comments

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.

We will be covering a few different features, available in shell scripting, in this article.

Functions

Often times, you will find that there are some operations that you perform repeatedly across different points in the script. It would be extremely useful to write this logic once and reuse it over and over in a quick and efficient manner. Functions allow us to do just that.

#!/bin/bash

#function syntx ----------
repeat() {
	echo "Function without the function keyword"
}

repeat 

#function with function keyword ----------
function message() {
	echo "The argument is $1"
}

message "Arun"

#function with a local variable
#--------------------------------------------------
function localVar() {
	local value="ABC"
	echo $value
}

localVar 

#function with an argument being passed in
#--------------------------------------------------
function report() {
	echo "Argument passed in: $1"
}

report "Value 1"

function argsParameters() {
	echo "\$# -> Number of arguments"
	echo "\$* -> All positional arguments as a single word"
	echo "\$@ -> All positional arguments as separate strings"
	echo "\$1 -> First argument"
	echo "\$_ -> last argument of previous command"
}

argsParameters 

#function returning value
#--------------------------------------------------
function operation() {
	echo "XYZ"
}

answer="$(operation)"
echo $answer

function retCode() {
	echo "Return code"
	return 10
}

retCode 
echo $?

Environment

#!/bin/bash

#list environment variables
echo "Print environment variables"
echo "--------------------------------------------------"
printenv 
echo ""


#print specific environment variable value
echo "Print specific environment variables"
echo "--------------------------------------------------"
printenv SHELL
printenv USER
printenv LOGNAME
printenv HOME
echo ""

#path to the printenv command
echo "Print path to printenv command"
echo "--------------------------------------------------"
which printenv

The output would look like:

Print environment variables
--------------------------------------------------
CR_RUNID=19455
TERM_PROGRAM=CodeRunner
CR_SANDBOXED=1
TERM=dumb
SHELL=/bin/zsh
TMPDIR=/var/folders/ts/gm470rbx4xv0t507dt7xmj7c0000gn/T/com.coderunnerapp.CodeRunner/
CR_INPUT=
CR_SCRIPTS_DIR=/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data/Library/Application Support/CodeRunner/Languages/Shell Script.crLanguage/Scripts
USER=arunpatwardhan
COMMAND_MODE=unix2003
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.P9J71uVoN9/Listeners
filename=envDemo.sh
__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0
CR_DEVELOPER_DIR=/Applications/CodeRunner.app/Contents/SharedSupport/Developer
CR_UNSAVED_DIR=/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data/Library/Application Support/CodeRunner/Unsaved
CR_LANGUAGE_DIR=/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data/Library/Application Support/CodeRunner/Languages/Shell Script.crLanguage
CR_ENCODING_NAME=utf-8
CR_FILENAME=envDemo.sh
PATH=/Applications/Xcode.app/Contents/Developer:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Applications/VMware Fusion.app/Contents/Public:/Library/Apple/usr/bin:/Applications/CodeRunner.app/Contents/SharedSupport/Developer/bin
__CFBundleIdentifier=com.coderunnerapp.CodeRunner
PWD=/Users/arunpatwardhan/Developer
APP_SANDBOX_CONTAINER_ID=com.coderunnerapp.CodeRunner
CFFIXED_USER_HOME=/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data
CR_FILE=/Users/arunpatwardhan/Developer/envDemo.sh
XPC_FLAGS=0x0
CR_TMPDIR=/var/folders/ts/gm470rbx4xv0t507dt7xmj7c0000gn/T/com.coderunnerapp.CodeRunner/CodeRunner
XPC_SERVICE_NAME=0
SHLVL=2
HOME=/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data
CR_SUGGESTED_OUTPUT_FILE=/var/folders/ts/gm470rbx4xv0t507dt7xmj7c0000gn/T/com.coderunnerapp.CodeRunner/CodeRunner/envDemo
CR_VERSION=62959
LOGNAME=arunpatwardhan
LC_CTYPE=UTF-8
CR_RUN_COMMAND=bash "$filename"
compiler=
CR_ENCODING=4
_=/usr/bin/printenv

Print specific environment variables
--------------------------------------------------
/bin/zsh
arunpatwardhan
arunpatwardhan
/Users/arunpatwardhan/Library/Containers/com.coderunnerapp.CodeRunner/Data

Print path to printenv command
--------------------------------------------------
/usr/bin/printenv

Redirection

We have already covered a little bit of redirection in an earlier article. There are some more redirection options available that we will look at out here.

Operator	Description	Example
>	Writes the output of the preceding command to the file	`echo "ABC" > file`
>>	Appends information to the file being pointed to another file	`echo "ABC" >> file`
\|	Passes the output of the preceding command to the next command	`ls -l \| grep "*.sh"`

Using the above redirections there are some interesting actions that we can perform.

Action	Description
`command >> /dev/null`	This will completely discard the output of the command.
`command 2>&1`	This will redirect stderr to stdout and show both together on stdout.
`command 1>&2`	This will redirect stdout to stderr and show both together on stderr.

Here document

One interesting application fo the redirection operator is the concept of here documents. A here document is used to send multiple lines of input to a command. The general structure is:

command << endOfMessageFlag
message
message
message
endOfMessageFlag

In this case the endOfMessageFlag is used to inform the command that the message has come to an end. A popular example is ‘EOF’ but any text can be used. Here are some examples of here documents.

#Writing to a file
cat << EOF >> /Users/Shared/temp.log
"This is a demo "
$(date)
EOF

The above script write the message within the ‘EOF’ to the file: /Users/Shared/temp.log. The message being:

This is a demo. 
Mon Sep 25 12:31:07 IST 2022

Here is another example:

#Multiple statements to a command
osascript << EOF
display dialog "Would you like to provide names for the folders or use the defaults instead?" buttons {"Custom", "Default"} default button 2 with icon POSIX file "/System/Library/CoreServices/HelpViewer.app/Contents/Resources/AppIcon.icns"
text returned of (display dialog "Enter the name of folder 1" default answer "Utilities" buttons {"OK"} default button 1 with title "Folder that will hold the utilities" with icon POSIX file "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/AlertStopIcon.icns")
EOF

The ‘here’ document allows us to send multiple AppleScript statements to ‘osascript‘.

Folder creator script update

Let us try to use some of these features in our folder creator script.

#!/bin/zsh

#-------------------------------------------------------------------------------------------------
#NAME: Folder creator
#AUTHOR: Arun Patwardhan
#CONTACT: arun@amaranthine.co.in
#DATE: 15th September 2022
#WEBSITE: https://github.com/AmaranthineTech/ShellScripts
#-------------------------------------------------------------------------------------------------

#LICENSE/TERMS AND CONDITIONS --------------------------------------------------------------------
#MIT License

#Copyright (c) Amaranthine 2021.

#ABOUT -------------------------------------------------------------------------------------------
# fileCreator.zsh
# 1.6
#-------------------------------------------------------------------------------------------------

#HELP/SUPPORT ------------------------------------------------------------------------------------
# You can get help by running the following commands.
# ./folderCreator.zsh -h
# ./folderCreator.zsh -help
# OR
# man folderCreator.zsh
# You can also view the log file for the same at: ~/Library/Logs/folderCreator_log_v1-6.log
#-------------------------------------------------------------------------------------------------

#HISTORY -----------------------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------
# Version 1.0: Basic script which creates the folders
# Version 1.1: Gives user the ability to specify the folder names at run time.
# Version 1.2: Adds safety checks to the scripts
# Version 1.3: Includes documentation as well as ability to get help.
# Version 1.4: Includes optimisation using for loop
# Version 1.5: Prompts the user in the GUI for names for the different folders.
# Version 1.6: Updated the log mechanism with the help of a function and here document.
#-------------------------------------------------------------------------------------------------

#These are the default values used for the folder names incase the user doesn't provide any.
TOOLS_FOLDER="Tools"
REPORTS_FOLDER="Reports"
HELP_FOLDER="Help"

#Script version number
VERSION_NUMBER="1.6"

#Command name
COMMAND_NAME="folderCreator.zsh"

NAME
----
$COMMAND_NAME — Folder creation utility SYNOPSIS
$COMMAND_NAME folder names [ verbs ]

VERBS
-----
[ −h −help] Both the options are used to invoke the help documentation.
[ −v −version] Both the options are used to get the version number of the folderCreator command.

REQUIREMENTS
------------
The following are the minimum requirements to get the script running.
Shell:\t\t zsh
OS:\t\t macOS Big Sur 11.4 or later
Dependencies:\t None

INSTALLATION
------------
$COMMAND_NAME can be installed anywhere you wish. However, there are certain locations that are recommended.
Location:\t /Library/Scripts/
Permissions: \t rwxr-xr-x

USAGE
-----
$COMMAND_NAME folder1 folder2 folder3
Will create folders with your own names.

$COMMAND_NAME -h OR $COMMAND_NAME -help
Will invoke the help utility.

$COMMAND_NAME -v OR $COMMAND_NAME -version
will print the version number in stdout.

WARNING/CAUTION
---------------
$COMMAND_NAME does not perform any validation of names. The only options that folderCreator accepts are -h and -help verbs or the -v and
-version verbs. If the script does not see the -h , -help or the -v , -version options then it will assume that the data being passed in is
the name of the folder. The user of the folderCreator command must ensure that the desired folder names are passed in. The user will also be
prompted, via the graphical user interface, if he/she wishes to provide the names for the folders. If yes, then there will be subsequent
prompts asking for the folder names.

EXAMPLES
--------
$COMMAND_NAME Resources Results Assistant
This will create 3 folders Resources , Results , Assistant , in the user’s home folder.

$COMMAND_NAME
This will create 3 folders with the default names

$COMMAND_NAME Apps
This will use the Apps name for the first folder but the default names for the last 2 folders.

NOTE
----
The user will be asked if he/she wishes to provide custom names in all the examples mentioned above. The user's value will always override
whatever is being provided to the script or defaults.

EXIT STATUS
-----------
In most situations, $COMMAND_NAME exits 0 on success"
exit 0
fi

PATH_TO_LOG="$HOME/Library/Logs/folderCreator_log_v1-6.log"

# Function to log activity
function recordActivity() {
cat << EOF >> $PATH_TO_LOG
[$(date)] $1
EOF
}

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

TODAY=$(date)

recordActivity "Starting"

#2. Check to see if the version number is
if [[ $1 == "-version" ]] || [[ $1 == "-v" ]]; then
echo "Version: $VERSION_NUMBER"
exit 0
fi

if [[ $2 != "" ]]; then
REPORTS_FOLDER=$2
fi

if [[ $3 != "" ]]; then
HELP_FOLDER=$3
fi

#4. We can prompt the user to see if they wish to provide folder names themselves. This will override any values provided as arguments.
userClicked=$(/usr/bin/osascript -e 'button returned of (display dialog "Would you like to provide names for the folders or use the defaults instead?" buttons {"Custom", "Default"} default button 2 with icon POSIX file "/System/Library/CoreServices/HelpViewer.app/Contents/Resources/AppIcon.icns")')

# if the user decides to provide custom names then go ahead and ask the user via GUI prompts. Otherwise use the values sent as arguments or defaults.
if [[ $userClicked == "Custom" ]]; then
recordActivity "The user decided to provide custom names."

TOOLS_FOLDER=$(/usr/bin/osascript -e 'text returned of (display dialog "Enter the name of folder 1" default answer "Utilities" buttons {"OK"} default button 1 with title "Folder that will hold the utilities" with icon POSIX file "/Users/Shared/Finder.icns")')

REPORTS_FOLDER=$(/usr/bin/osascript -e 'text returned of (display dialog "Enter the name of folder 2" default answer "Tools" buttons {"OK"} default button 1 with title "Folder that will hold the tools" with icon POSIX file "/Users/Shared/Finder.icns")')

HELP_FOLDER=$(/usr/bin/osascript -e 'text returned of (display dialog "Enter the name of folder 3" default answer "Help" buttons {"OK"} default button 1 with title "Folder that will hold the support documents" with icon POSIX file "/Users/Shared/Finder.icns")')

recordActivity "User provided: $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER"
else
recordActivity "User decided to use default values: $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER"
fi

#5. Go to the home folder.
cd $HOME

#6. Check to see if each of the folders exists. If it exists then do not create it. Else create the folder.
recordActivity "Creating folders: $TOOLS_FOLDER, $REPORTS_FOLDER, $HELP_FOLDER"

for item in $TOOLS_FOLDER $REPORTS_FOLDER $HELP_FOLDER; do
if [[ -d $item ]]; then
recordActivity "Not creating $item as it already exists."
else
recordActivity "Creating $item"
mkdir $item
fi

#7. Create the task completion file inside each folder.
recordActivity "Creating hidden file for $item folder."
cd $item
#8. Generate the file names based on the folder names.
touch ".$item-FolderCreated"
cd ..
done

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

One of the big advantages with using a function and a here document to generate log files is that we can change the format and structure simply by modifying the function. The message itself remains unique.

We have seen some really interesting features in this article. In the next article we will take scripting a little further by exploring Arrays and dictionaries

Download

You can download the completed script from here.

Using Swift Package Manager

April 9, 2018 / Arun Patwardhan / Leave a comment

About Swift Package Manager

The Swift Package Manager is the tool used to build Applications and Libraries. it streamlines the process of managing multiple Modules & Packages. Before we go ahead and learn to use Swift Package Manager we need to get familiar with some basic terminology.

Modules

Modules are used to specify a namespace and used to control access to that particular piece of code. Everything in Swift is organised as a module. An entire app can fit into a module or an app can be made using multiple modules. The fact that we can build modules using other modules means that reusing code becomes a lot easier. So, when we make an iOS App with Xcode and Swift. The entire app is considered a single module.

Targets

Targets are the end product that we want to make. So an app for iOS is a separate target. A library is a target. An app for macOS is a separate target. You can have many targets. Some can be for testing purposes only.

Packages

Packages group the necessary source files together. A package can contain more than one target. Normally one would create a package for a family of products. For example: you want to make a photo editing app that runs on macOS & iOS. You would create one package for it. That package would have 2 targets: an iOS App & a macOS App.

Products

This is a categorisation of your packages. There are 2 types of products. Executables or Libraries. A library contains the module which can be reused elsewhere. Executables are application that run & may make use of other modules.

Dependencies

Dependencies are the modules or the pieces of code that are required to make the different targets within the package. These are normally provided as URLs.

End Products

*NOTE: Before you get started you must be familiar with Setting up Swift on Linux. If you haven’t done that then please go through the updated article: UPDATE: Swift on Linux. This also makes use of Swift Package Manager.

Example

So let us get started with an example. We are going to learn how to create:

a library package called ErrorTypes
a library package, called MathOperations, that uses the ErrorTypes library package
an executable package called Calc that makes use of the MathOperations package.

We will see how to create all three elements. Also I have uploaded the ErrorTypes & MathOperations packages to the http://www.github.com repository to demonstrate the use of dependencies. You can also create your own local git repositories if you wish.

To illustrate the folder hierarchy: I have created a folder called “Developer” in my Ubuntu linux home folder. Within that I have created a folder called “SPMDEMO“. All the paths that I will be using will be with reference to these folders. You should see a structure like this:

/home/admin/Developer/SPMDEMO/ErrorTypes
/home/admin/Developer/SPMDEMO/MathOperations
/home/admin/Developer/SPMDEMO/Calc

You are free to follow this exercise using your own folder locations. Just modify the paths accordingly.

swift package init
swift package init --type executable
swift build

If you need help with the commands run:

swift package --help
swift --help

Creating a Package

First let us start off by creating the ErrorTypes package.
```
mkdir ErrorTypes
```
Navigate to the folder and create the package:
```
cd ErrorTypes
swift package init
```
By default init will create a library package type.
Navigate to the folder containing the source files:
```
cd ./Sources/ErrorTypes/
```

Open the ErrorTypes.swift file and write the following code

public enum ErrorCodes : Error
{
     case FileNotFound(String)
     case DivideByZero(String)
     case UnknownError(String)
}

public struct MathConstants
{
     static let pi : Float = 3.14159
     static let e  : Float = 2.68791
}

Feel free to add some code of your own. The above is just an example.

Run the command to build to make sure that there aren’t any issues. You shouldn’t have any as there are no dependencies of any kind. Its a simple straightforward piece of code.
```
swift build
```
If everything is fine check your code into a git repository. This can be local or on the web. Remember that we will need the URL to this repository.
Navigate back to the SPMDEMO folder.
```
cd ~/Developer/SPMDEMO/
```
Create a folder called MathOperations.
```
mkdir MathOperations
```
Navigate to the newly created folder and run the command to create a library package.
```
cd MathOperations
swift package init
```
Navigate to the sources folder:
```
cd ./Sources/MathOperations/
```

Open the MathOperations.swift file and write the following code.

import ErrorTypes

public struct MathOperations
{
     public static func add(Number num1 : Int, with num2 : Int) -> Int
     {
          return num1 + num2
     }

     public static func mult(Number num1 : Int, with num2 : Int) -> Int
     {
          return num1 * num2
     }

     public static func div(Number num1 : Int, by num2 : Int) throws -> Int
     {
          guard num2 > 0
          else
          {
          throw ErrorCodes.DivideByZero("You are dividing by zero. The second argument is incorrect.")
          }

          return num1 / num2
     }

     public static func sub(_ num1 : Int, from num2 : Int) -> Int
     {
          return num2 - num1
     }
}

Before we build we need to modify the Packages.swift file to indicate there is a dependency.
Notice that in the MathOperations.swift file we are importing a module called ErrorTypes. We just created it. But just because we created it doesn’t mean it will be added automatically. We need to pull that module into our own

Also notice that I have provided access specifiers “public” everywhere. This ensures that the code written in one module is accessible in the other.

Navigate to the MathOperations parent folder.
```
cd ~/Developer/SPMDEMO/MathOperations/
```

Open the Packages.swift file and make the changes as shown below:

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(name: "MathOperations",
     products: [
          // Products define the executables and libraries produced by a package, and make them visible to other packages.
          .library(name: "MathOperations", targets: ["MathOperations"]),
     ],

     dependencies: [
          // Dependencies declare other packages that this package depends on.
          .package(url:"https://github.com/AmaranthineTech/ErrorTypes.git", from:"1.0.0"),
     ],

     targets: [
          // Targets are the basic building blocks of a package. A target can define a module or a test suite.
          // Targets can depend on other targets in this package, and on products in packages which this package depends on.
          .target(name: "MathOperations", dependencies: ["ErrorTypes"]),
          .testTarget(name: "MathOperationsTests", dependencies:   ["MathOperations"]),]
)

Once these changes are made save the file and run the command
```
swift build
```
If you typed everything correctly then you should see the source code for the ErrorTypes module being pulled in and the build being successful.Here are some common mistakes:
– Forgetting to write the import ErrorTypes statement
– Error in the URL
– The from tag not matching the tag in the repository
– Access specifiers are incorrect or missing
– Not mentioning the dependencies in the target
Just like with the ErrorTypes module create a git repository for the MathOperations module.
Now let us make the Calc executable that will use the MathOperations library. First navigate back to the SPMDEMO folder and create a folder called Calc.
```
cd ~/Developer/SPMDEMO/
mkdir Calc
```
This time we are going to create an executable package. Run the command:
```
swift package init --type executable
```
This also creates a similar folder structure as in the case of the library.
Navigate to the folder containing the main.swift file.
```
cd ./Sources/Calc/
```

Modify the main.swift file as shown below:

import MathOperations

//testing addition
var result : Int = MathOperations.add(Number: 33, with: 29)
print("Result of adding 33 with 29 is: \(result)")

//testing multiplication
result = MathOperations.mult(Number: 33, with: 29)
print("Result of multiplying 33 with 29 is: \(result)")

//testing division
do
{
     result = try MathOperations.div(Number: 33, by: 0)
     print("Result of dividing 33 by 29 is: \(result)")
}
catch let error
{
     print("ERROR: \(error)")
}

//testing subtraction
result = MathOperations.sub(3, from: 29)print("Result of subtracting 3 from 29 is: \(result)")

Navigate back to the main Calc folder.
```
cd ~/Developer/SPMDEMO/Calc/
```

Modify the Packages.swift file as shown below:

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(name: "Calc",
dependencies: [
     // Dependencies declare other packages that this package depends on.
     .package(url: "https://github.com/AmaranthineTech/MathOperations.git", from: "1.0.1"),
],
targets: [
     // Targets are the basic building blocks of a package. A target can define a module or a test suite.
     // Targets can depend on other targets in this package, and on products in packages which this package depends on.
     .target(name: "Calc", dependencies: ["MathOperations"]),
]
)

Save the file and run the build command:
```
swift build
```
Like before you should see both the MathOperations & ErrorType module being pulled in. We are ready to run the executable. Navigate to the debug folder which contains the executable. Make sure you are in the main Calc folder when you run this command.
```
cd ./build/debug/
```
You should see an executable file called Calc. Run it.
```
./Calc
```
If everything went okay then you should see the output on the console.

As you can see it is pretty straightforward to develop Applications written in Swift on Linux.

Adding System Modules

In the previous example we saw how to import our own custom made modules. However, there are some modules provided by the system which offers functionality we may wish to use. For example if we wanted to use the random number generator in our application we would need to use the random() method. This is in the glib module.

Quickly create a package called SystemLibs. This is an executable.

Write the following code in the main.swift.

#if os(Linux)
import Glibc
#else
import Darwin.C
#endif
extension Int
{
     func toString() -> String
     {
          return "\(self)"
     }
}

var luckyNumber : Int = Int(random())

var luckyNumberStr : String = luckyNumber.toString()

print("The lucky number is \(luckyNumberStr)")

Build the code and run the executable.

Adding system modules is direct and simple. The glibc module contains aspects of the standard library. The condition check is to make sure that we are importing the correct module based on the system that we are developing the application on.

Handling Sub-dependencies

As we saw in the earlier example, sub dependencies are handled automatically. So when our Calc application marked the MathOperations module as a dependency it was pulled during the build. However, the MathOperations module itself marked ErrorTypes module as a dependency. We did not have to modify the Packages.swift file belonging to Calc to indicate that ErrorTypes module also needs to be pulled. This was handled automatically by Swift Package Manager.

Conclusion

In this article we have seen:

How to create a library package
How to create a library package that depends on another library package
How to create an executable that depends on a library package
How to import the system Glibc module into our executables.

The Swift Package Manager simplifies many aspects of the development process for us. Many of the things we have discussed also work on macOS. Going forward reusing code and planning for the same should be done keeping Swift Package Manager in mind.

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Using Swift Package Manager

About Swift Package Manager

Modules

Targets

Packages

Products

Dependencies

End Products

Example

Creating a Package

Adding System Modules

Handling Sub-dependencies

Conclusion

Loops

Handling loops

For loops

While loops

Example

Video

Download

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Functions

Environment

Redirection

Here document

Folder creator script update

Download

Share this:

Like this:

About Swift Package Manager

Modules

Targets

Packages

Products

Dependencies

End Products

Example

Creating a Package

Adding System Modules

Handling Sub-dependencies

Conclusion

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Like this: