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<a name="Accessing-Global-Variables-in-Oct_002dFiles"></a>
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<p>
Next: <a href="Calling-Octave-Functions-from-Oct_002dFiles.html#Calling-Octave-Functions-from-Oct_002dFiles" accesskey="n" rel="next">Calling Octave Functions from Oct-Files</a>, Previous: <a href="Sparse-Matrices-in-Oct_002dFiles.html#Sparse-Matrices-in-Oct_002dFiles" accesskey="p" rel="prev">Sparse Matrices in Oct-Files</a>, Up: <a href="Oct_002dFiles.html#Oct_002dFiles" accesskey="u" rel="up">Oct-Files</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Accessing-Global-Variables-in-Oct_002dFiles-1"></a>
<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>get_global_value</code> and <code>set_global_value</code>.
<code>get_global_value</code> takes two arguments, the first is a string representing
the variable name to obtain. The second argument is a boolean argument
specifying what to do if no global variable of the desired name is found.
An example of the use of these two functions is
</p>
<div class="example">
<pre class="verbatim">#include <octave/oct.h>
DEFUN_DLD (globaldemo, args, , "Global Demo")
{
octave_value retval;
int nargin = args.length ();
if (nargin != 1)
print_usage ();
else
{
std::string s = args(0).string_value ();
if (! error_state)
{
octave_value tmp = get_global_value (s, true);
if (tmp.is_defined ())
retval = tmp;
else
retval = "Global variable not found";
set_global_value ("a", 42.0);
}
}
return retval;
}
</pre><pre class="example">
</pre></div>
<p>An example of its use is
</p>
<div class="example">
<pre class="example">global a b
b = 10;
globaldemo ("b")
⇒ 10
globaldemo ("c")
⇒ "Global variable not found"
num2str (a)
⇒ 42
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