docs(Shell): explain what a .sh file is with examples

What
- Documented .sh files as shell scripts used in Linux and macOS environments.
- Key details:
  - Plain text files with `.sh` extension.
  - Require execution permission via chmod +x file.sh.
  - Contain Unix shell commands executed sequentially.
  - Commonly used for automation, system tasks, and launching applications.
- Included examples:
  1. Simple hello world script:
     ```bash
     #!/bin/bash
     echo "Hello, World from Shell Script!"
     ```
  2. Script to open IntelliJ IDEA with a project file:
     ```bash
     #!/bin/bash
     "/opt/idea-IU-2023.3/bin/idea.sh" "/home/user/Projects/JavaTutorials/src/Main.java" &
     ```

Why
- Provides beginners and developers with clear understanding of what .sh files are and how to use them.
- Illustrates both basic scripting (Hello World) and practical real-world usage (launching IDE with a project).
- Highlights cross-cutting importance of shell scripts in automation and software workflows.

How
- Explained role of shebang (`#!/bin/bash`) as interpreter declaration.
- Showed how commands inside .sh run in sequence.
- Explained `&` operator for running tasks in background.
- Outlined execution flow:
  1. Write commands in a plain text file.
  2. Save file with `.sh` extension.
  3. Give execute permission with `chmod +x`.
  4. Run script with `./file.sh`.

Logic
- Inputs: plain text commands.
- Outputs: execution of those commands on terminal.
- Flow:
  - Shell reads file → executes commands line by line.
  - If background operator `&` used, process detaches from current terminal session.
- Edge cases:
  - If script lacks execute permission, error: “Permission denied.”
  - Wrong shebang path leads to "No such file or directory."
- Complexity / performance: negligible; execution speed depends on commands inside.
- Concurrency / thread-safety: multiple scripts can be run concurrently in different processes.

Real-life applications
- Automating repetitive commands (compilation, deployment, backups).
- Starting servers or development tools.
- Batch operations on files and directories.
- CI/CD pipelines in software projects.
- System maintenance and monitoring tasks.

Notes
- A .sh script can run in any POSIX-compliant shell (bash, zsh, dash, etc.).
- Best practice: make scripts portable by using `#!/bin/sh` for general compatibility.
- Scripts can include logic (if-else, loops, functions) making them powerful automation tools.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Tips And Tricks/What is a .sh File.txt

@@ -0,0 +1,24 @@
+What is a .sh File?
+
+A .sh file is a shell script used in Linux and macOS.
+It contains a series of Unix commands executed by the shell (bash, zsh, etc.).
+
+Key Features of a .sh File:
+- Plain text file with .sh extension.
+- Must be given execute permission (chmod +x file.sh).
+- Runs commands in sequence inside the terminal.
+- Used for automation, system tasks, software builds, etc.
+
+Example 1: Simple Hello World
+#!/bin/bash
+echo "Hello, World from Shell Script!"
+
+Example 2: Open IntelliJ IDEA on Linux
+#!/bin/bash
+"/opt/idea-IU-2023.3/bin/idea.sh" "/home/user/Projects/JavaTutorials/src/Main.java" &
+
+How It Works:
+- #!/bin/bash specifies the interpreter.
+- Path "/opt/idea-IU-2023.3/bin/idea.sh" is IntelliJ startup script.
+- Second path points to the Java file to open.
+- & runs the program in the background.