Is there a tool for analyzing what a bash script does line by line? : <p>I need to understand few bash scripts from time to time, but I'm not a bash expert and I'd like to learn it during reading each script. Is there a tool which can tell me what each script line does?</p>

<p>for example, it can tell me what each line does, and through what grammar </p>

<pre><code>GPU_ID=$1
NET=$2
NET_lc=${NET,,}
DATASET=$3
</code></pre>

<p>for now I'm searching google by keywords "bash ${var,,}", but the search engine isn't smart enough to give me any thing useful, I can't find even the correct naming of this grammar.</p>

<p>Please don't tell me that asking on StackOverflow is my best option for all such kind of beginner's questions.</p>
