&gt; For example, grep and egrep are two commands that perform very similar functions and are therefore implemented as a single program.<p>Not everywhere:<p><pre><code>    $ ls -li &#x2F;bin&#x2F;grep &#x2F;bin&#x2F;egrep &#x2F;bin&#x2F;fgrep
    37748784 -rwxr-xr-x 1 root root 183696 Jan 18  2014 &#x2F;bin&#x2F;egrep
    37748788 -rwxr-xr-x 1 root root 138352 Jan 18  2014 &#x2F;bin&#x2F;fgrep
    37748794 -rwxr-xr-x 1 root root 191952 Jan 18  2014 &#x2F;bin&#x2F;grep
</code></pre>
(That&#x27;s on Ubuntu 14.04.)