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<h4 class="subsection" id="Dual_002dPurpose-Executable-Scripts-and-Octave-Functions-1"><span>2.6.2 Dual-Purpose Executable Scripts and Octave Functions<a class="copiable-link" href="#Dual_002dPurpose-Executable-Scripts-and-Octave-Functions-1"> ¶</a></span></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 class="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 class="emph">are</em> passed
to the function and these override the default.
</p>
<p>Additionally, the file must end with the extension <samp class="file">.m</samp> so that the
interpreter will recognize it as an Octave function. Finally, the output from
<code class="code">argv</code> is a cell array of strings. It may be necessary to convert this
to a numeric value with <code class="code">str2double</code> or <code class="code">str2num</code> before processing.
</p>
<p>As a complete example, consider the following code located in the file
<samp class="file">mysin.m</samp>.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">#! /bin/octave -qf
function retval = mysin (x = str2double (argv(){end}))
retval = sin (x)
endfunction
</pre></div></div>
<p>This can be called from the shell with
</p>
<div class="example">
<pre class="example-preformatted">mysin.m 1.5
</pre></div>
<p>or from Octave with
</p>
<div class="example">
<pre class="example-preformatted">mysin (1.5)
</pre></div>
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