This is a recommended "learning path" for Bash Scripting:

• Bash – Hello World
• Bash – Variables
• Bash – Comments
• Bash – Quotes
• Bash – Debugging
• Bash – Exit Codes
• Bash – Command Arguments
• Bash – Include Files
• Bash – Shell Commands
• Bash – User Input
• Bash – Arithmetic Operations
• Bash – Numeric Comparisons
• Bash – String Comparisons
• Bash – If-else
• Bash – For Loop
• Bash – While Loop
• Bash – Case
• Bash – Functions