#!/bin/bash

filename=$1

if [ -z "$filename" ]; then
  echo "You must provide a file for the script."
  echo "Example:"
  echo "     `basename $0` foo.mp4"
  exit 1
fi

if [ ! -f "$filename" ]; then
  echo "The file provided does not exist."
  exit 1
fi

friendly_filename=`sed -E 's/[^[:alnum:][:space:]]+/_/g' <<< "$filename"`

ffmpeg -i $filename -vframes 1 ${friendly_filename}-image.png