🔧 1. Shell Scripting (bash, sh)

What is a Shell?

A shell is a command-line interpreter that lets you interact with the operating system. Think of it as a translator between you and the kernel.

• bash (Bourne Again Shell) – most widely used in Linux.
• sh (Bourne Shell) – older, minimal, used for compatibility.

Shell Scripting Concept:

Instead of typing commands one by one, you store them in a script file (.sh) so they execute sequentially. This is automation for repetitive tasks like:

• Backups
• Software installation
• Monitoring

Key points in shell scripts:

• Shebang (#!) – tells Linux which interpreter to use (e.g., #!/bin/bash)
• Variables – store values for reuse
• Control structures – if, for, while loops
• Functions – group commands

Example script concept:

#!/bin/bash
USER_NAME="Suhas"
echo "Welcome, $USER_NAME"
if [ $(date +%u) -gt 5 ]; then
    echo "It's weekend!"
else
    echo "It's a weekday."
fi

Save as myscript.sh, then:

chmod +x myscript.sh
./myscript.sh