Single-line comments in a Bash script are the important annotation that makes the script more readable. You can use a single-line comment to add an explanation of codes or disable some particular codes for a while. So, let me turn your attention to this article which will provide a detailed interpretation of single-line comments in Bash to you.
- Learning about single-line comments in Bash.
- Getting ideas about some practical executions of single-line comments in Bash script.
What Are Single Line Comments in Bash?
Single-line comments refer to the comments where the line starts with a hash symbol (#) and are placed before or after the code in the Bash script. These comments are kind of short and concise. Moreover, single-line comments are only for quoting a simple brief of code lines and are not executed by the interpreter or compiler.
2 Cases of Single Line Comments in Bash Scripting
Single-line comments are the less explanatory Bash comments. These are related to two points: i) Bash hashing, and ii) Inline comments. A little introduction to these two concerns is given below:
Case 1: Bash Hashing in Case of Single Line Comments
In Bash, hash (#) is the symbol for commenting out a line. A single-line comment prefixed with the hash symbol (#) adds an explanatory text without affecting the execution of codes within the Bash script. Following is an example of bash hashing in case of single-line comments with step by step procedure:
Steps to Follow >
➊ Open your Ubuntu Terminal.
➋ To open a script in the nano text editor, write the command below:
➌ Hereafter, write the following script inside the editor:
Script (hash-single.sh) >
From the above image, you can see three single-line comments which are prefixed with the hash symbol.
#!/bin/bash # This is a single-line comment # This is another single-line comment # This is one more single-line comment
Case 2: Inline Comments in Case of Single Line Comments
The single-line comments that are used at the end of the coded line are specifically called inline comments. These are used at the same line of the code starting with a hash sign without moving to the next line. Below is a simple example of inline comments in case of single-line comments:
Script (single-line.sh) >
You can see the single-line comments as inline comments in the above image.
#!/bin/bash number=20 echo "The number is: $number" #Display the current number number=$((number+5)) #Increment the ‘number’ variable echo "The updated number is: $number" #Display the updated number
3 Practical Examples of Single-line Comments in Bash
Single-line comments can be of help in various practical schemes. Now, I am going to mention some real clarifications of single-line comments in the Bash script in the following section:
Example 1: Bash Single Line Comments for Troubleshooting
For any troubleshooting purpose within Bash scripts, debugging with single-line comments is quite helpful. Below is an example of single-line comments aiding in debugging:
Script (troubleshoot.sh) >
You can observe the step-by-step results and identify the unexpected bugs within your codes using single-line comments like the snapshot above.
#!/bin/bash #Calculating the sum of numbers from 5 to a given number #Prompt user for entering an input read -p "Enter a positive integer:" number #Check if the input is a positive integer if [[ ! "$number" =~ ^[1-9][0-9]*$ ]]; then echo "Invalid input. Please enter a positive integer." exit 1 fi #Initialize the sum variable sum=0 #Calculate the sum using a loop for (( i=1; i<=number; i++ )); do sum=$((sum + i)) #Add present value of i to the sum echo "Current Sum: $sum" #Debugging: print current sum for each iteration done #Display the output echo "The sum of numbers from 5 to $number is: $sum"
Example 2: Bash Single Line Comments for Educational Purposes
You can use single-line comments for educational purposes too. These can serve as great documented resources for any kind of tutorial. Here is an easy implementation of single-line comments on finding the factorial of a given number:
Script (factorial.sh) >
From the image, you can see that the single-line comments have turned the program quite easy explaining each section of the code.
#!/bin/bash #Calculating the factorial of a given number #Prompt user for entering an input read -p "Enter a positive integer: " number #Check if the input is a positive integer if [[ ! "$number" =~ ^[1-9][0-9]*$ ]]; then echo "Invalid input. Please enter a positive integer." exit 1 fi #Initialize the factorial variable factorial=1 #Calculate factorial using a loop for (( i=1; i<=number; i++ )); do factorial=$((factorial * i)) #Multiply factorial with current value of i done #Display the output echo "The factorial of $number is: $factorial"
Example 3: Bash Single Line Comments for Security Purposes
Single-line comments emphasize the security of a Bash script. Here’s an example of single-line comments on restricting unauthorized access to the Bash script:
Script (security.sh) >
The single-line comments underlined in the above image help to define the unusual users easily.
#!/bin/bash #IMPORTANT: Confirm that only authorized users can access the script. #This script performs sensitive operations & must be protected. #Check if the user is authorized if [[ "$user" != "admin" ]]; then echo "Error! You cannot run this script." exit 1 fi
To summarize, single-line comments as an essential feature serve to clarify codes or programming within a Bash script. So, count on this guide and make a practice of commenting out your code concisely.
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