Valheim Server Discord Alerts

logwatcher.sh

#!/bin/bash

##########################
# Change these variables #
##########################
FILE="/path/to/console.log"
WEBHOOK_URL="CHANGEME"
STEAMKEY="CHANGEME"
##########################

### script logic ###
# array to store steam ids and map to player names
declare -A SteamID
# initialize global variables
lastSteamID=0
havePlayerName=0 

# begin watching the log file and check each new line
tail -Fn0 $FILE | \
while read -r line ; do
    # check for the matching lines we want to look into further
        if grep -iq "Closing socket\|Got handshake from client\|Got character ZDOID from" <<< "$line"
        then
            # tokenize the line sp;it by colons so easier to process
            IFS=':' tokens=( $line )
            # we're only interested in the text of the log entry
            entry=$(echo "${tokens[3]}" | xargs)
            # get rid of windows carriage return
            entry="$(echo $entry | sed 's/\r//g')"
            if grep -iq "Got handshake from client" <<< "$entry"
            then
                # grab everything in the entry past the matching text and mark that we have a recent steam id
                lastSteamID=$(sed -n -e 's/^.*Got handshake from client //p' <<< "$entry")
                haveSteamID=1
            elif grep -iq "Got character ZDOID from" <<< "$entry"
            then
                # grab everything in the entry past the matching text and mark that we have a recent player name
                playerName=$(sed -n -e 's/^.*Got character ZDOID from //p' <<< "$entry")
                havePlayerName=1
                # add the name and id to the array for recall later
                SteamID[$lastSteamID]=$playerName
                # if we have both a recent name and recent steam id go ahead and assume we have a new client that connected and send alert
                if [[ havePlayerName -eq 1 && haveSteamID -eq 1 ]]
                then
                    # grab the steam id profile url and name
                    response=$(curl -Gs -d "steamids=${lastSteamID}" -d "key=${STEAMKEY}" https://api.steampowered.com/ISteamUser/GetPlayerSummaries/v2/)
                    profile=$(jq '.response.players[0].profileurl' <<< $response | tr -d "\"")
                    personaname=$(jq '.response.players[0].personaname' <<< $response | tr -d "\"")
                    # output to terminal
                    echo "Player ${playerName} (probably ${lastSteamID}) has joined the server - Steam profile ${personaname} (${profile})"
                    # send to Discord
                    curl -X POST --data "{\"content\": \"Player ${playerName} (probably ${lastSteamID}) has joined the server - Steam profile ${personaname} (${profile})\"}" --header "Content-Type:application/json" "$WEBHOOK_URL"
                    # reset variables so we're not sending alerts without it being a new connection
                    havePlayerName=0
                    haveSteamID=0
                fi
            elif grep -iq "Closing socket" <<< "$entry"
            then
                # grab everything in the entry past the matching text
                socket=$(sed -n -e 's/^.*Closing socket //p' <<< "$entry")
                # check that it's an actual socket closing
                if [ "$socket" != "0" ]
                then
                    # output to terminal
                    echo "SteamID ${socket} left the server (was probably ${SteamID[$socket]})"
                    # send to Discord
                    curl -X POST --data "{\"content\": \"SteamID ${socket} left the server (was probably ${SteamID[$socket]})\"}" --header "Content-Type:application/json" "$WEBHOOK_URL"
                fi
            else
                # this should never happen but is included for failover
                echo "unhandled entry:" "$entry"
            fi
        fi
done

This script monitors a Valheim server log (in my case generated by linuxgsm, but could be saved via redirection when starting the server in normal scenarios) and triggers a Discord webhook when someone joins or leaves. It's not exactly accurate at all times because there are no log entries on join or part that match, so we have to guess using the most recent steamid handshake with the player name, then remember it for later when the steamid closes the socket and we can guess who it was.

I found there were player connection refreshes without new handshakes so I made it not report unless both were collected and then clearing those values after a discord alert is sent.