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<hr>
<span id="Accessing-Global-Variables-in-Oct_002dFiles-1"></span><h4 class="subsection">A.1.7 Accessing Global Variables in Oct-Files</h4>

<p>Global variables allow variables in the global scope to be accessed.  Global
variables can be accessed within oct-files by using the support functions
<code><span class="nolinebreak">global_varval</span></code><!-- /@w --> and <code><span class="nolinebreak">global_assign</span></code><!-- /@w --> from the current
interpreter&rsquo;s symbol table.  Both functions take as first argument a string
representing the variable name to be obtained or assigned.  The second
argument of <code><span class="nolinebreak">global_assign</span></code><!-- /@w --> is the value to be assigned.  An
example of the use of these two functions is
</p>
<div class="example">
<pre class="verbatim">#include &lt;octave/oct.h&gt;
#include &lt;octave/interpreter.h&gt;

DEFMETHOD_DLD (globaldemo, interp, args, , &quot;Global Demo&quot;)
{
  if (args.length () != 1)
    print_usage ();

  octave_value retval;

  std::string s = args(0).string_value ();

  octave::symbol_table&amp; symtab = interp.get_symbol_table ();

  octave_value tmp = symtab.global_varval (s);

  if (tmp.is_defined ())
    retval = tmp;
  else
    retval = &quot;Global variable not found&quot;;

  symtab.global_assign (&quot;a&quot;, 42.0);

  return retval;
}
</pre></div>

<p>An example of its use is
</p>
<div class="example">
<pre class="example">global a b
b = 10;
globaldemo (&quot;b&quot;)
&rArr; 10
globaldemo (&quot;c&quot;)
&rArr; &quot;Global variable not found&quot;
num2str (a)
&rArr; 42
</pre></div>




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