little script to set stl as default starter for every steam game. works with a copy of the steam config

STLsetDefault.sh

#!/bin/bash

YOURID=0
SUD="$HOME/.steam/steam/userdata/"
LCVDFO="$SUD/$YOURID/config/localconfig.vdf"
LCVDF="/tmp/localconfig.vdf"

LOPT="\\\t\t\t\t\t\t\"LaunchOptions\"		\"stl %command%\""

if [ -n "$1" ]; then
	if [ -f "$SUD/$1/config/localconfig.vdf" ]; then
		echo "argument1 $1 seems to be your steamID"
		YOURID="$1"
		LCVDFO="$SUD/$YOURID/config/localconfig.vdf"
	else
		echo "argument1 $1 doesn't seem to be your steamID - $SUD/$1/config/localconfig.vdf does not exist!"
	fi
fi

if [ "$YOURID" -eq 0 ]; then
	echo "you have to edit YOURID first, to match the directory name of your steamID or provide it as commandline argument 1- exit"
	echo "maybe:"
	find "$SUD" -maxdepth 1 -type d -name "[1-9]*"
	exit 1
fi

if [ ! -f "$LCVDF" ]; then
	echo "$LCVDF doesn't exist - copying the original"
	if [ ! -f "$LCVDFO" ]; then
		echo "$LCVDFO doesn't exist as well - giving up"
		exit 1
	else
	cp "$LCVDFO" "$LCVDF"
	fi
fi

sed -i '/LaunchOptions/d' "$LCVDF"
sed -i '/"Play[Tt]ime"/i '"$LOPT"'' "$LCVDF"

echo "done - you might want to check if the file $LCVDF looks valid before using it!"
echo "make sure to close steam before copying the file!"
echo "create a backup of your unmodified $LCVDFO f.e. with this command:"
echo "cp $LCVDFO $LCVDFO.bak"
echo "if you dare update to the modified stl version with this command (you at your own risk!):"
echo "cp $LCVDF $LCVDFO"

There's no support for this script and I would generally recommend to not blindly execute any scripts when the basics are missing to read and understand the script.

So is there no other way,then go to add the launch options I want for every game individually?
Because that would take long.

Yes it would take long. AFAIK there's no other way to mass alter steams localconfig.vdf
A short description of what the script does:
It requires your steamID as argument1 to get the full path to the localconfig.vdf
The steamID can simply be found by following the path the script tries to glue together,
but it also suggests one if none is given as arg1.
When it finds the localconfig.vdf it creates a copy and only works with the copy,
so your original file is unmodified.
As echoed in the last lines it is up to you what you do with the modified file.

@frostworx Steam seems to use playTime instead of Playtime now for line 38.

@Confetti-Camouflage Thanks, should be fixed.