Shell scripting in macOS – Part 7: Miscellaneous

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.

OperatorDescriptionExample
>Writes the output of the preceding command to the fileecho "ABC" > file
>>Appends information to the file being pointed to another fileecho "ABC" >> file
|Passes the output of the preceding command to the next commandls -l | grep "*.sh"

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

ActionDescription
command >> /dev/nullThis will completely discard the output of the command.
command 2>&1This will redirect stderr to stdout and show both together on stdout.
command 1>&2This 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
#-------------------------------------------------------------------------------------------------

#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
# 1.6
#-------------------------------------------------------------------------------------------------

#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_v1-6.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.
#-------------------------------------------------------------------------------------------------

#-------------------------------------------------------------------------------------------------
# ------------------------------ 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="1.6"

#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_v1-6.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.

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.

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.

COPYRIGHT  
---------
Copyright (c) Amaranthine 2015-2021. All rights reserved. https://amaranthine.in

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

#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

#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!"
	
#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------
#-------------------------------------------------------------------------------------------------
# ------------------------------ END OF SCRIPT ---------------------------------------------------

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.

Advertisement

2 thoughts on “Shell scripting in macOS – Part 7: Miscellaneous

  1. Pingback: Shell scripting in macOS – Part 1 | Arun Patwardhan's Blog

  2. Pingback: Shell scripting in macOS – Part 8: Arrays & Dictionaries | Arun Patwardhan's Blog

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s