title: Is `command -v` option required in a POSIX shell? Is posh compliant with POSIX?
body: <p>I am using <a href="https://packages.debian.org/jessie/posh" rel="noreferrer">posh</a> to test my shell script that I want to run successfully on any POSIX compliant shell. While doing so, I found that the <code>command -v</code> option is not supported in posh. Neither is <code>type</code>.</p>
  
  <p>I understand that <code>type</code> is not supported because it is not required by POSIX. This is discussed at <a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=397601#10" rel="noreferrer">https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=397601#10</a>.</p>
  
  <blockquote>
    <p>"type" is an X/Open extension; note the XSI marking in the POSIX
    standard.  Since it is not required by POSIX or by debian policy, posh
    doesn't implement it.</p>
  </blockquote>
  
  <p><a href="http://pubs.opengroup.org/onlinepubs/009695399/utilities/type.html" rel="noreferrer">http://pubs.opengroup.org/onlinepubs/009695399/utilities/type.html</a> confirms this. See the <code>[XSI]</code> margin code in the synopsis.</p>
  
  <p>But I fail to understand why <code>command -v</code> option is not supported in posh.</p>
  
  <p>Some mentions that <code>command -v</code> is optional at <a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=218530#131" rel="noreferrer">https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=218530#131</a>.</p>
  
  <blockquote>
    <p>And "command -v" is an optional functionality according to
    <a href="http://www.opengroup.org/onlinepubs/009695399/utilities/" rel="noreferrer">http://www.opengroup.org/onlinepubs/009695399/utilities/</a>
    just to mention it.</p>
  </blockquote>
  
  <p>But I am unable to confirm this at <a href="http://pubs.opengroup.org/onlinepubs/009695399/utilities/command.html" rel="noreferrer">http://pubs.opengroup.org/onlinepubs/009695399/utilities/command.html</a>. Can you see anything here that indicates that <code>-v</code> option is optional in <code>command</code>?</p>
  
  <p>If not, is <code>posh</code> is not compliant with POSIX?</p>