publish discord auto updater

README.md

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+# Discord Automatic Updater
+This is a small shell script and systemd service that automatically check for discord updates in the background. It updates Discord by editing `/usr/share/discord/resources/build_info.json` to the most recent version number - the content of the updates are installed by Discord itself when launched. 
+
+Currently, this has only been tested with the debian-based Discord package. It may work with the `.rpm` installer as well - let me know if you try it. Update the appropriate environment variables in `update-discord.sh`. 
+
+## Setup
+Run this from inside the Git repo: 
+```sh
+# move the script to a system location and make it executable
+sudo mkdir -p /usr/local/bin
+sudo cp ./update-discord.sh /usr/local/bin/update-discord
+sudo chmod 755 /usr/local/bin/update-discord
+
+# create the systemd service
+sudo cp ./update-discord.service /etc/systemd/system/update-discord.service
+
+# create the systemd timer
+sudo cp ./update-discord.timer /etc/systemd/system/update-discord.timer
+
+sudo systemctl daemon-reload
+sudo systemctl enable --now update-discord.timer
+```
+You can manually test it too:
+```sh
+# check schedule
+systemctl list-timers | grep discord
+
+# manually trigger and check logs
+sudo systemctl start update-discord.service
+journalctl -u update-discord.service
+```
+

update-discord.service

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+[Unit]
+Description=Update Discord
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/bin/update-discord
+TimeoutSec=5min

update-discord.sh

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+#!/bin/bash
+
+################
+# CHANGE THESE #
+################
+
+# path to your build_info.json file; include the file name
+DISCORD_BUILD_INFO_PATH="/usr/share/discord/resources/build_info.json"
+
+# for debian-based linux distributions (.deb installers)
+DISCORD_PLATFORM="linux"
+DISCORD_FORMAT="deb"
+
+###########################
+# DON'T CHANGE THIS STUFF #
+###########################
+
+# check for sudo
+if [ $(id -g) -ne 0 ]; then
+	echo "Please run as sudo"
+	exit 2
+fi
+
+apt-get update && apt-get install -y jq
+
+# get currently installed version of Discord
+ver_current=$(jq -r ".version" "$DISCORD_BUILD_INFO_PATH")
+echo "Discord version $ver_current installed"
+
+# check latest available Discord version by looking at the headers of the latest Discord download URL
+pre_ver_available=$(curl -s -I "https://discord.com/api/download?platform=$DISCORD_PLATFORM&format=$DISCORD_FORMAT" | grep location)
+
+# trim everything before and after the version number
+ver_available="${pre_ver_available#*linux/}"
+ver_available="${ver_available%/*}"
+
+echo "Discord version $ver_available available"
+
+if [ "$ver_current" = "$ver_available" ] ; then
+	echo "Discord is up to date!"
+	exit 0
+fi
+
+echo "Discord is not up to date, editing $DISCORD_BUILD_INFO_PATH"
+
+jq ".version = \"$ver_available\"" $DISCORD_BUILD_INFO_PATH > discord_build_info_tmp.json
+chmod 644 discord_build_info_tmp.json
+mv discord_build_info_tmp.json "$DISCORD_BUILD_INFO_PATH"
+
+killall Discord

update-discord.timer

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+[Unit]
+Description=Run Discord updater daily and after boot
+
+[Timer]
+OnCalendar=*-*-* 03:00:00
+OnBootSec=1min
+Persistent=true
+
+[Install]
+WantedBy=timers.target