Coding with the Shell

The command-line interface (shell) is a powerful and efficient environment for software development. It’s commonly used for writing, compiling (for compiled languages like C++), and running code. This section provides basic examples for C++ and Python.

C++

Create the Source Code: Use a text editor (like nano or vim) to create a C++ source file (usually with a .cpp extension).
```
nano hello.cpp  # Create a new file named hello.cpp
```
Write the Code: Enter your C++ code into the file. Here’s a simple “Hello, World!” example:
```
#include <iostream>

int main() {
    std::cout << "Hello, World!" << std::endl;
    return 0;
}
```
Note: Using using namespace std; is generally discouraged in larger projects, as it can lead to naming conflicts. It’s better to use std::cout, std::endl, etc. I’ve used the more explicit form here.
Save and Exit (Nano): Press Ctrl+O, then Enter (to confirm the filename), then Ctrl+X.
Compile the Code: Use the g++ compiler to compile your code into an executable.
```
g++ hello.cpp -o hello  # Compile hello.cpp and create an executable named 'hello'
```
Explanation:
- g++: The GNU C++ compiler.
- hello.cpp: The source code file.
- -o hello: The -o option specifies the name of the output file (the executable). If you omit -o, the default output file name is a.out.
Installation (if needed):
- Debian/Ubuntu: sudo apt install g++
- CentOS/Fedora: sudo yum install gcc-c++ / sudo dnf install gcc-c++

Run the Executable:

./hello  # Execute the compiled program

Sample Output:

Hello, World!

Python

Create the Source Code: Use a text editor to create a Python source file (usually with a .py extension).
```
nano hello.py  # Create a new file named hello.py
```
Write the Code: Enter your Python code. Here’s a “Hello, World!” example:
```
print("Hello, World!")
```
Save and Exit (Nano): Press Ctrl+O, then Enter, then Ctrl+X.
Run the Script: Use the python3 interpreter to execute your script.
```
python3 hello.py  # Run the Python script
```
Sample Output:
```
Hello, World!
```
Note: On many systems, python might refer to Python 2, which is outdated. It’s best to use python3 explicitly to ensure you’re using Python 3.

Installation (if needed - usually pre-installed, but sometimes you need to install it explicitly):
- Debian/Ubuntu: sudo apt install python3
- CentOS/Fedora: sudo yum install python3 / sudo dnf install python3

Other Languages

The general workflow for other languages is similar:

Write Code: Use a text editor to create your source file.
Compile (if necessary): Use the appropriate compiler for your language (e.g., javac for Java, gcc for C).
Run: Execute the compiled program (or use the interpreter for interpreted languages like Ruby, Perl, etc.).

Example (Java):

# 1. Create HelloWorld.java (using nano, vim, etc.)
# public class HelloWorld {
#     public static void main(String[] args) {
#         System.out.println("Hello, World!");
#     }
# }

# 2. Compile:
javac HelloWorld.java  # Creates HelloWorld.class

# 3. Run:
java HelloWorld