C&nbsp;function call which
indicated an error condition. If the optional <tt>newerr</tt> argument
is present, the error number is set to the new value and the previous
value is returned.
</p>
<p>
This function offers a portable and OS-independent way to get and set the
error number. Note that only <em>some</em> C&nbsp;functions set the error
number. And it's only significant if the function actually indicated an
error condition (e.g. with a return value of <tt>-1</tt> or
<tt>NULL</tt>). Otherwise, it may or