twitch bash script

#!/bin/bash
#bash script utilizing livestreamer to play twitch streams
#usage "twitch.sh <stream name>"
#or just invoke the script and enter the stream name you want
#
#save in /usr/bin
#and type "chmod +x twitch.sh"
#you can also add it as an alias in ~/.bashrc or in a custom file, loaded by .bashrc in the format:
#
#alias twitch='twitch.sh'
#alias twi='twitch.sh'
#
#then just type twitch wcs and enjoy :)

if [ -n $1 ]; then
    str_input=$1
fi

if [ -z $1 ]; then
        echo -n "Stream name? : "
        read str_input
fi

echo "Loading twitch stream: twitch.tv/$str_input !"

str="livestreamer twitch.tv/space best"
r=${str//space/$str_input}
$r