title: Avoid temp file in bash command
body: <p>I'm trying to avoid the creation of a temp file (in the example <code>t12.txt</code>) using some bash tricks, to no avail.</p>
  
  <p>Suppose two files <code>t1.txt</code> and <code>t2.txt</code>, with some text lines.</p>
  
  <p>Example of a command working:</p>
  
  <pre><code>$ cat t1.txt t2.txt &gt; t12.txt
  $ tac t2.txt t1.txt | tac | diff - t12.txt
  </code></pre>
  
  <p>Now I'm trying to avoid the creation of t12.txt using anything, from pipes to weird redirects.</p>
  
  <p>Commands I tried in different orders and tests are things like: <code>$(cat t1.txt t2.txt)</code> or <code>&lt; &lt;(cat t1.txt t2.txt)</code>.</p>
  
  <p>Any creative suggestion here? Ty.</p>