Difference between Sh and bash in linux

<<–2/”>a href=”https://exam.pscnotes.com/5653-2/”>p>Let’s break down the differences between sh and bash in a comprehensive way.

Introduction

In the realm of Linux shells, sh (the Bourne shell) and bash (the Bourne Again shell) are prominent players. While both provide a command-line interface for interacting with the operating system, they have distinct characteristics that influence how they’re used for scripting and interactive work.

Key Differences (Table Format)

Feature	sh (Bourne Shell)	bash (Bourne Again Shell)
History	Limited command history	Extensive command history with features like searching and editing
Array Support	Basic array support	Full-featured array support with flexible indexing and operations
String Manipulation	Basic string operations	Advanced string manipulation features like substring expansion
Parameter Expansion	Limited parameter expansion features	Enhanced parameter expansion capabilities
Brace Expansion	Does not support brace expansion	Supports brace expansion for generating combinations of strings
Process Substitution	Does not support process substitution	Supports process substitution to treat command output as files
Command Line Editing	Limited command-line editing with line-oriented editing	Enhanced command-line editing with vi or emacs-style editing
Job Control	Basic job control	More sophisticated job control with features like backgrounding
Shell Initialization	Simple initialization process	Customizable initialization process with profiles (.bashrc, etc.)
POSIX Compliance	Stricter adherence to POSIX standards	Adheres to POSIX while offering extensions
Default Shell on Unix	Traditionally the default shell on many Unix systems	Often the default interactive shell on Linux systems

Advantages and Disadvantages

Shell	Advantages	Disadvantages
sh	Lightweight, faster execution, stricter adherence to POSIX, ideal for portable scripts	Limited features, less convenient for interactive use, older syntax
bash	Feature-rich, enhanced interactive use, modern syntax, widely adopted, extensive community support	Can be slightly slower due to its larger feature set, may include non-POSIX features

Similarities

Both are command-line interpreters that execute commands and scripts.
Both support basic shell scripting constructs like variables, conditionals, loops, and functions.
Both are available on most Unix-like operating systems.

FAQs

Which shell should I use for scripting?
For simple, portable scripts that need to run on various Unix systems, sh is a good choice. If you need advanced features or are primarily targeting Linux environments, bash is often preferred.
Can I run bash scripts with sh?
In many cases, yes. However, if your bash script relies on features not present in sh, it might fail. It’s generally a good practice to explicitly specify #!/bin/bash as the first line of your script if it requires bash-specific features.
How do I switch between shells?
You can use the chsh command to change your default shell. To start an interactive session with a different shell temporarily, simply type the shell’s name (e.g., bash) in the terminal.
Is bash a superset of sh?
Mostly, yes. Bash is designed to be mostly compatible with sh while adding many extensions.
What is POSIX compliance?
POSIX (Portable Operating System Interface) is a set of standards for Unix-like operating systems. A POSIX-compliant shell adheres to these standards, ensuring greater portability of scripts across different systems.

Let me know if you’d like more details on any specific aspect!