List the file extensions found for a given directory tree, default current directory

find-extensions.sh

#!/bin/bash

# Function to display usage information
usage() {
  echo "Usage: $0 [-d | --directory] <directory>"
  echo "  -d, --directory   Specify the directory to search (default: current directory)"
  exit 1
}

# Default directory is the current directory
DIR="."

# Parse command-line arguments
while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
  -d | --directory )
    shift; DIR="$1"
    ;;
  *)
    usage
    ;;
esac; shift; done
if [[ "$1" == '--' ]]; then shift; fi

# Check if directory exists
if [[ ! -d "$DIR" ]]; then
  echo "Error: Directory '$DIR' does not exist."
  usage
fi

# Find file extensions used in the specified directory and its subdirectories
find "$DIR" -type f | awk -F. '{print $NF}' | sort -u