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Next: <a href="Script-Files.html#Script-Files" accesskey="n" rel="next">Script Files</a>, Previous: <a href="Default-Arguments.html#Default-Arguments" accesskey="p" rel="prev">Default Arguments</a>, Up: <a href="Functions-and-Scripts.html#Functions-and-Scripts" accesskey="u" rel="up">Functions and Scripts</a> &nbsp; [<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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<hr>
<a name="Function-Files-1"></a>
<h3 class="section">11.9 Function Files</h3>
<a name="index-function-file"></a>

<p>Except for simple one-shot programs, it is not practical to have to
define all the functions you need each time you need them.  Instead, you
will normally want to save them in a file so that you can easily edit
them, and save them for use at a later time.
</p>
<p>Octave does not require you to load function definitions from files
before using them.  You simply need to put the function definitions in a
place where Octave can find them.
</p>
<p>When Octave encounters an identifier that is undefined, it first looks
for variables or functions that are already compiled and currently
listed in its symbol table.  If it fails to find a definition there, it
searches a list of directories (the <em>path</em>) for files ending in
<samp>.m</samp> that have the same base name as the undefined
identifier.<a name="DOCF5" href="#FOOT5"><sup>5</sup></a>  Once Octave finds a file with a name that matches,
the contents of the file are read.  If it defines a <em>single</em>
function, it is compiled and executed.  See <a href="Script-Files.html#Script-Files">Script Files</a>, for more
information about how you can define more than one function in a single
file.
</p>
<p>When Octave defines a function from a function file, it saves the full
name of the file it read and the time stamp on the file.  If the time
stamp on the file changes, Octave may reload the file.  When Octave is
running interactively, time stamp checking normally happens at most once
each time Octave prints the prompt.  Searching for new function
definitions also occurs if the current working directory changes.
</p>
<p>Checking the time stamp allows you to edit the definition of a function
while Octave is running, and automatically use the new function
definition without having to restart your Octave session.
</p>
<p>To avoid degrading performance unnecessarily by checking the time stamps
on functions that are not likely to change, Octave assumes that function
files in the directory tree
<samp><var>octave-home</var>/share/octave/<var>version</var>/m</samp>
will not change, so it doesn&rsquo;t have to check their time stamps every time the
functions defined in those files are used.  This is normally a very good
assumption and provides a significant improvement in performance for the
function files that are distributed with Octave.
</p>
<p>If you know that your own function files will not change while you are
running Octave, you can improve performance by calling
<code>ignore_function_time_stamp (&quot;all&quot;)</code>, so that Octave will
ignore the time stamps for all function files.  Passing
<code>&quot;system&quot;</code> to this function resets the default behavior.
</p>

<a name="XREFedit"></a><dl>
<dt><a name="index-edit"></a>: <em></em> <strong>edit</strong> <em><var>name</var></em></dt>
<dt><a name="index-edit-1"></a>: <em></em> <strong>edit</strong> <em><var>field</var> <var>value</var></em></dt>
<dt><a name="index-edit-2"></a>: <em><var>value</var> =</em> <strong>edit</strong> <em>(&quot;get&quot;, <var>field</var>)</em></dt>
<dt><a name="index-edit-3"></a>: <em><var>value</var> =</em> <strong>edit</strong> <em>(&quot;get&quot;, &quot;all&quot;)</em></dt>
<dd><p>Edit the named function, or change editor settings.
</p>
<p>If <code>edit</code> is called with the name of a file or function as its
argument it will be opened in the text editor defined by <code>EDITOR</code>.
</p>
<ul>
<li> If the function <var>name</var> is available in a file on your path and that
file is modifiable, then it will be edited in place.  If it is a system
function, then it will first be copied to the directory <code>HOME</code> (see
below) and then edited.  If no file is found, then the m-file variant,
ending with <code>&quot;.m&quot;</code>, will be considered.  If still no file is found,
then variants with a leading <code>&quot;@&quot;</code> and then with both a leading
<code>&quot;@&quot;</code> and trailing <code>&quot;.m&quot;</code> will be considered.

</li><li> If <var>name</var> is the name of a function defined in the interpreter but not
in an m-file, then an m-file will be created in <code>HOME</code> to contain that
function along with its current definition.

</li><li> If <code><var>name</var>.cc</code> is specified, then it will search for
<code><var>name</var>.cc</code> in the path and try to modify it, otherwise it will
create a new <samp>.cc</samp> file in the current directory.  If <var>name</var>
happens to be an m-file or interpreter defined function, then the text of
that function will be inserted into the .cc file as a comment.

</li><li> If <samp><var>name</var>.ext</samp> is on your path then it will be edited, otherwise
the editor will be started with <samp><var>name</var>.ext</samp> in the current
directory as the filename.  If <samp><var>name</var>.ext</samp> is not modifiable,
it will be copied to <code>HOME</code> before editing.

<p><strong>Warning:</strong> You may need to clear <var>name</var> before the new definition
is available.  If you are editing a .cc file, you will need to execute
<code>mkoctfile <samp><var>name</var>.cc</samp></code> before the definition will be
available.
</p></li></ul>

<p>If <code>edit</code> is called with <var>field</var> and <var>value</var> variables, the
value of the control field <var>field</var> will be set to <var>value</var>.
</p>
<p>If an output argument is requested and the first input argument is
<code>get</code> then <code>edit</code> will return the value of the control field
<var>field</var>.  If the control field does not exist, edit will return a
structure containing all fields and values.  Thus, <code>edit (&quot;get&quot;,
<code>&quot;all&quot;</code>)</code> returns a complete control structure.
</p>
<p>The following control fields are used:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>home</samp>&rsquo;</dt>
<dd><p>This is the location of user local m-files.  Be sure it is in your path.
The default is <samp>~/octave</samp>.
</p>
</dd>
<dt>&lsquo;<samp>author</samp>&rsquo;</dt>
<dd><p>This is the name to put after the &quot;## Author:&quot; field of new functions.  By
default it guesses from the <code>gecos</code> field of the password database.
</p>
</dd>
<dt>&lsquo;<samp>email</samp>&rsquo;</dt>
<dd><p>This is the e-mail address to list after the name in the author field.  By
default it guesses <code>&lt;$LOGNAME@$HOSTNAME&gt;</code>, and if <code>$HOSTNAME</code>
is not defined it uses <code>uname -n</code>.  You probably want to override
this.  Be sure to use the format <code><a href="mailto:user@host">user@host</a></code>.
</p>
</dd>
<dt>&lsquo;<samp>license</samp>&rsquo;</dt>
<dd>
<dl compact="compact">
<dt>&lsquo;<samp>gpl</samp>&rsquo;</dt>
<dd><p>GNU General Public License (default).
</p>
</dd>
<dt>&lsquo;<samp>bsd</samp>&rsquo;</dt>
<dd><p>BSD-style license without advertising clause.
</p>
</dd>
<dt>&lsquo;<samp>pd</samp>&rsquo;</dt>
<dd><p>Public domain.
</p>
</dd>
<dt>&lsquo;<samp>&quot;text&quot;</samp>&rsquo;</dt>
<dd><p>Your own default copyright and license.
</p></dd>
</dl>

<p>Unless you specify &lsquo;<samp>pd</samp>&rsquo;, edit will prepend the copyright statement
with &quot;Copyright (C) YYYY Author&quot;.
</p>
</dd>
<dt>&lsquo;<samp>mode</samp>&rsquo;</dt>
<dd><p>This value determines whether the editor should be started in async mode
(editor is started in the background and Octave continues) or sync mode
(Octave waits until the editor exits).  Set it to <code>&quot;sync&quot;</code> to start
the editor in sync mode.  The default is <code>&quot;async&quot;</code>
(see <a href="Controlling-Subprocesses.html#XREFsystem">system</a>).
</p>
</dd>
<dt>&lsquo;<samp>editinplace</samp>&rsquo;</dt>
<dd><p>Determines whether files should be edited in place, without regard to
whether they are modifiable or not.  The default is <code>false</code>.
</p></dd>
</dl>
</dd></dl>


<a name="XREFmfilename"></a><dl>
<dt><a name="index-mfilename"></a>: <em></em> <strong>mfilename</strong> <em>()</em></dt>
<dt><a name="index-mfilename-1"></a>: <em></em> <strong>mfilename</strong> <em>(&quot;fullpath&quot;)</em></dt>
<dt><a name="index-mfilename-2"></a>: <em></em> <strong>mfilename</strong> <em>(&quot;fullpathext&quot;)</em></dt>
<dd><p>Return the name of the currently executing file.
</p>
<p>When called from outside an m-file return the empty string.
</p>
<p>Given the argument <code>&quot;fullpath&quot;</code>, include the directory part of the
filename, but not the extension.
</p>
<p>Given the argument <code>&quot;fullpathext&quot;</code>, include the directory part of
the filename and the extension.
</p></dd></dl>


<a name="XREFignore_005ffunction_005ftime_005fstamp"></a><dl>
<dt><a name="index-ignore_005ffunction_005ftime_005fstamp"></a>: <em><var>val</var> =</em> <strong>ignore_function_time_stamp</strong> <em>()</em></dt>
<dt><a name="index-ignore_005ffunction_005ftime_005fstamp-1"></a>: <em><var>old_val</var> =</em> <strong>ignore_function_time_stamp</strong> <em>(<var>new_val</var>)</em></dt>
<dd><p>Query or set the internal variable that controls whether Octave checks
the time stamp on files each time it looks up functions defined in
function files.
</p>
<p>If the internal variable is set to <code>&quot;system&quot;</code>, Octave will not
automatically recompile function files in subdirectories of
<samp><var>octave-home</var>/lib/<var>version</var></samp> if they have changed since they were last compiled, but will recompile other function files in the search path if they change.
</p>
<p>If set to <code>&quot;all&quot;</code>, Octave will not recompile any function files
unless their definitions are removed with <code>clear</code>.
</p>
<p>If set to <code>&quot;none&quot;</code>, Octave will always check time stamps on files to
determine whether functions defined in function files need to recompiled.
</p></dd></dl>


<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="Manipulating-the-Load-Path.html#Manipulating-the-Load-Path" accesskey="1">Manipulating the Load Path</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Subfunctions.html#Subfunctions" accesskey="2">Subfunctions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Private-Functions.html#Private-Functions" accesskey="3">Private Functions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Nested-Functions.html#Nested-Functions" accesskey="4">Nested Functions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Overloading-and-Autoloading.html#Overloading-and-Autoloading" accesskey="5">Overloading and Autoloading</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Function-Locking.html#Function-Locking" accesskey="6">Function Locking</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Function-Precedence.html#Function-Precedence" accesskey="7">Function Precedence</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<div class="footnote">
<hr>
<h4 class="footnotes-heading">Footnotes</h4>

<h3><a name="FOOT5" href="#DOCF5">(5)</a></h3>
<p>The &lsquo;<samp>.m</samp>&rsquo; suffix was chosen for compatibility
with <small>MATLAB</small>.</p>
</div>
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