Basic Command Line Argument Parsing in Bash

#!/bin/bash
# Script demonstrating basic command-line argument parsing

# Default values
NAME="World"
VERBOSE=false
INPUT_FILE=""

# Parse command-line options
# ':' after an option indicates it requires an argument.
# The leading ':' in the optstring makes getopts silent about errors,
# allowing custom error handling via '?' and ':' cases.
while getopts ":n:vf:" opt; do
  case ${opt} in
    n )
      NAME="$OPTARG"
      ;;
    v )
      VERBOSE=true
      ;;
    f )
      INPUT_FILE="$OPTARG"
      ;;
    \? )
      echo "Invalid option: -$OPTARG" >&2
      exit 1
      ;;
    : )
      echo "Option -$OPTARG requires an argument." >&2
      exit 1
      ;;
  esac
done
shift $((OPTIND -1)) # Shift positional parameters past the options

# Script logic based on parsed arguments
echo "Hello, $NAME!"

if [ "$VERBOSE" = true ]; then
  echo "Verbose mode is enabled."
  echo "Input file: ${INPUT_FILE:-'Not specified'}"
fi

if [ -n "$INPUT_FILE" ]; then
    if [ -f "$INPUT_FILE" ]; then
        echo "Processing file: $INPUT_FILE"
        # Add file processing logic here
    else
        echo "Error: Input file '$INPUT_FILE' not found." >&2
        exit 1
    fi
fi

# Remaining arguments (if any)
if [ $# -gt 0 ]; then
    echo "Remaining arguments: $*"
fi

# Example Usage:
# ./myscript.sh -n "Alice" -v
# ./myscript.sh -f data.txt
# ./myscript.sh -n "Developer" -v -f project.config arg1 arg2