<p>Looking in the gnuwin32/bin directory, there is an odd-looking program file named <code>[.exe</code></p>

<p>I couldn't find it in the documentation, gnuwin32.sourceforge.net or in a google search, so I ran it and got:</p>

<pre><code>$ [
[: missing `]'
$
</code></pre>

<p>so I gave it ] as a parameter and got</p>

<pre><code>$ [ ]

$
</code></pre>

<p>It didn't complain, so I assumed it was on the right track. I tried:</p>

<pre><code>$ [ hello ]
</code></pre>

<p>again, no complaints. so I tried an arithmetic expression:</p>

<pre><code>$ [ 1 + 1 ]
[: +: binary operator expected
$
</code></pre>

<p>I tried a bunch of different combinations, including prefix &amp; postfix notation but nothing seemed to work. What does this thing do?</p>

```
```
test a
```
```
==
```
```
[ a ]
```
```
It's just sugar
Edit: To clarify, that's the conditional syntax, e.g. [ "a" = "a" ]