title: Adding --ignore-failed-read to tar causes "unknown function modifier" error
body: <p>I'm using the tar command in UNIX to perform backups of particular directories. However, some directories contain files/sub-directories which the current user doesn't have any read permissions on. As a result the tar command is returning a non 0 exit code. </p>
  
  <p>I came across the following modifier in the man pages '--ignore-failed-read', which suppresses the non 0 exit code when encountering files it cannot read. However, whenever I try using it I get the error 'unknown function modifier'. </p>
  
  <p>Could anyone help me out here? </p>
  
  <p>my tar command looks something like this: </p>
  
  <pre><code>tar --create --ignore-failed-read --file=test.tar my_dir
  </code></pre>