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<div class="subsection" id="Dual_002dPurpose-Executable-Scripts-and-Octave-Functions">
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<p>
Previous: <a href="Passing-Arguments-to-Executable-Scripts.html" accesskey="p" rel="prev">Passing Arguments to Executable Scripts</a>, Up: <a href="Executable-Octave-Programs.html" accesskey="u" rel="up">Executable Octave Programs</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Dual_002dPurpose-Executable-Scripts-and-Octave-Functions-1"></span><h4 class="subsection">2.6.2 Dual-Purpose Executable Scripts and Octave Functions</h4>
<p>To write m-files that can act as executable programs when called from the shell
or as normal functions when called from within Octave, use default input
arguments initialized with the <code>argv</code> function.
</p>
<p>If a function is called from the shell Octave will not pass any input
parameters to the function and therefore the default argument is used. But
when a function is called from the interpreter any arguments <em>are</em> passed
to the function and these override the default.
</p>
<p>Additionally, the file must end with the extension <samp>.m</samp> so that the
interpreter will recognize it as an Octave function. Finally, the output from
<code>argv</code> is a cell array of strings. It may be necessary to convert this
to a numeric value with <code>str2double</code> or <code>str2num</code> before processing.
</p>
<p>As a complete example, consider the following code located in the file
<samp>mysin.m</samp>.
</p>
<div class="example">
<pre class="example">#! /bin/octave -qf
function retval = mysin (x = str2double (argv(){end}))
retval = sin (x)
endfunction
</pre></div>
<p>This can be called from the shell with
</p>
<div class="example">
<pre class="example">mysin.m 1.5
</pre></div>
<p>or from Octave with
</p>
<div class="example">
<pre class="example">mysin (1.5)
</pre></div>
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