Bash Scripting vs Shell Scripting

Bash scripting and shell scripting are essential skills for anyone working in a Unix-like environment. Although these terms are often used interchangeably, they refer to different scopes and functionalities. Understanding the nuances between bash scripting and shell scripting can significantly enhance your ability to automate tasks, manage systems, and write efficient code.

In this tutorial you will learn:

The differences between bash scripting and shell scripting
How to write basic scripts in both bash and shell
Advanced features unique to bash scripting

Software Requirements and Linux Command Line Conventions
Category	Requirements, Conventions or Software Version Used
System	Unix-like operating system
Software	Bash (Bourne Again SHell)
Other	Basic knowledge of command-line interface
Conventions	# – requires given linux commands to be executed with root privileges either directly as a root user or by use of `sudo` command $ – requires given linux commands to be executed as a regular non-privileged user

Shell scripting is a broad term that encompasses scripts written for any shell in Unix-based systems, such as sh, ksh, csh, tcsh, and bash. These different shells have their own syntax and features, allowing users to write scripts that can automate tasks, manipulate files, and interact with the system. For instance, the Bourne shell (sh) is known for its simplicity and portability, making it suitable for scripts that need to run on various Unix-like systems. The Korn shell (ksh) offers additional features such as improved scripting capabilities and built-in arithmetic operations. The C shell (csh) provides a syntax similar to the C programming language, which can be beneficial for those familiar with C.

Bash scripting, however, refers specifically to scripts written for the Bash (Bourne Again SHell) environment, which is one of the most popular and widely used shells. Bash scripting leverages advanced features like associative arrays, string manipulation, and enhanced control structures. This makes Bash a powerful tool for complex scripting tasks that require more functionality than the traditional Bourne shell.

While shell scripting can involve multiple shell environments, bash scripting is focused exclusively on leveraging the advanced features of Bash. This focus allows for more sophisticated and efficient scripts when working within the Bash environment. However, it’s important to note that scripts written for Bash may not always be compatible with other shells due to the specific features and syntax Bash provides.

Pros and Cons of Bash Scripting vs Shell Scripting

Bash Scripting

Pros	Cons
Advanced features like associative arrays and string manipulation	Not as portable across all Unix-like systems
Enhanced control structures for complex scripts	Scripts may not be compatible with other shells
Better error handling and debugging capabilities	Can be more complex and harder to learn for beginners
Wide community support and extensive documentation	Specific to Bash environment, limiting flexibility

Shell Scripting (Bourne Shell)

Pros	Cons
High portability across various Unix-like systems	Lacks advanced features available in Bash
Simpler syntax, making it easier to learn for beginners	Less efficient for complex scripting tasks
Compatibility with multiple shell environments	Basic error handling and debugging capabilities
Suitable for basic and straightforward scripting needs	Limited community support compared to Bash

Both Bash scripting and shell scripting have their own advantages and disadvantages. Bash scripting is powerful and feature-rich, making it suitable for complex tasks, but it sacrifices portability and simplicity. On the other hand, shell scripting with the Bourne shell is highly portable and easier to learn, but it lacks the advanced features of Bash. Depending on your specific needs and environment, you can choose the scripting language that best suits your requirements.

Example Comparison

To illustrate the differences between bash scripting and shell scripting, consider the following example which demonstrates how to check if a file exists in both the Bourne shell (sh) and Bash:

Bourne Shell (sh) Script:

#!/bin/sh
if [ -f "/path/to/file" ]
then
    echo "File exists."
else
    echo "File does not exist."
fi

This script checks if a file exists at a specified path. The syntax is straightforward and compatible with the Bourne shell, ensuring it runs on various Unix-like systems.

Bash Script:

#!/bin/bash
FILE="/path/to/file"
if [[ -f "$FILE" ]]
then
    echo "File exists."
else
    echo "File does not exist."
fi

This script also checks if a file exists but uses a more advanced test syntax available in Bash. The double square brackets [[ ]] provide additional features and are more flexible than the single brackets [ ] used in the Bourne shell.

Bash Scripting Examples

Bash scripting allows you to take advantage of Bash-specific features, such as arrays and advanced string manipulation. Here are some examples to illustrate these capabilities:

String Manipulation: A script to demonstrate string manipulation in Bash.
```
#!/bin/bash
STRING="Hello, World!"
echo ${STRING,,} # Convert to lowercase
echo ${STRING^^} # Convert to uppercase
```
This example shows how to manipulate strings in Bash, converting them to lowercase and uppercase using Bash parameter expansion.
Array Example: A script to demonstrate the use of arrays in Bash.
```
#!/bin/bash
declare -A array
array=([key1]="value1" [key2]="value2")
echo "Array element: ${array[key1]}"
```
This example shows how to declare and use associative arrays in Bash, a feature not available in other shell environments like sh.
Function Example: A script to demonstrate the use of functions in Bash.
```
#!/bin/bash
function greet {
    echo "Hello, $1!"
}
greet "World"
```
This script defines a simple function in Bash that takes an argument and prints a greeting message.

Shell Scripting Examples

Shell scripting covers a broader range of shells, often using more basic syntax to ensure compatibility across different environments. Here are some examples:

String Manipulation: A script to demonstrate basic string manipulation in the Bourne shell.
```
#!/bin/sh
STRING="Hello, World!"
echo "$(echo $STRING | tr '[:upper:]' '[:lower:]')" # Convert to lowercase
echo "$(echo $STRING | tr '[:lower:]' '[:upper:]')" # Convert to uppercase
```
This example shows how to manipulate strings in the Bourne shell by using the tr command to convert strings to lowercase and uppercase.
Array Simulation Example: A script to demonstrate how to simulate arrays in the Bourne shell.
```
#!/bin/sh
array="value1 value2"
set -- $array
echo "Array element: $1"
```
This example shows how to simulate arrays in the Bourne shell by using positional parameters.
Function Example: A script to demonstrate the use of functions in the Bourne shell.
```
#!/bin/sh
greet() {
    echo "Hello, $1!"
}
greet "World"
```
This script defines a simple function in the Bourne shell that takes an argument and prints a greeting message.

Conclusion

Understanding the differences between bash scripting and shell scripting is crucial for writing efficient and compatible scripts in Unix-like environments. While bash scripting offers advanced features unique to Bash, shell scripting provides broader compatibility across different shells. By mastering both, you can enhance your scripting capabilities and handle a wider range of tasks and environments.

Bash Scripting vs Shell Scripting: Differences, Examples, and Comparisons