download_workshop.sh

#!/bin/bash
# ./download_workshop.sh [steam workshop URL]
set -e

workshop_id=$(echo "$1" | grep -Po 'steamcommunity\.com/(sharedfiles|workshop)/filedetails/.*id=\K(\d+)')
if [ -z "$workshop_id" ]; then
  echo "Could not extract ID from given URL"
  exit 1
fi

details=$(curl -s "https://api.steampowered.com/ISteamRemoteStorage/GetPublishedFileDetails/v1/" -F "itemcount=1" -F "publishedfileids[0]=$workshop_id")

name=$(echo "$details" | jq ".response.publishedfiledetails[0].title")
if [ "$name" = "null" ]; then
  echo "Could not find workshop item \"$workshop_id\". It might require logging in to an account that owns the game."
  echo "Full output:"
  echo "$details" | jq ".response.publishedfiledetails[0]"
  exit 1
fi

app_id=$(echo "$details" | jq ".response.publishedfiledetails[0].consumer_app_id") 
echo "Downloading $name"

tmp=$(mktemp -d)
trap 'rm -r "$tmp"' EXIT

steamcmd +force_install_dir "$tmp" +login anonymous +workshop_download_item "$app_id" "$workshop_id" +quit &> /dev/null

if [ -d "$PWD/$workshop_id" ]; then
  rm -r "$PWD/$workshop_id"
fi
mv "$tmp/steamapps/workshop/content/$app_id/$workshop_id" "$PWD"
if [ "$?" -eq 0 ]; then
  echo "Downloaded $workshop_id to \"$PWD\""
fi