title: what does $# -eq in shell mean
body: <p>I am new to shell script, in below shell script</p>
  
  <pre><code>#!/usr/bin/env sh
  PREFIX=${PREFIX-/usr/local}
  VERSIONS_DIR=$PREFIX/n/versions
  
  test -d $VERSIONS_DIR || mkdir -p $VERSIONS_DIR
  
  if test $# -eq 0; then
  </code></pre>
  
  <p>what does <code>$# -eq 0</code> mean in this shell script?</p>