<li><a href="#sys_eval"><code>sys_eval</code></a> - executes an arbitrary command, and returns it's output.</li>

<li><a href="#sys_exec"><code>sys_exec</code></a> - executes an arbitrary command, and returns it's exit code.</li>

<a name="sys_eval"></a><h2>sys_eval</h2>

<p>

<code>sys_eval</code> takes one command string argument and executes it, returning its output.

</p>

<h3>Syntax</h3>

<pre>sys_eval(<b>arg1</b>)</pre>

<h3>Parameters and Return Values</h3>

<dl>

<dt><code><b>arg1</b></code></dt>

<dd>

A command string valid for the current operating system or execution environment.

</dd>

<dt>returns</dt>

<dd>

Whatever output the command pushed to the standard output stream.

</dd>

</dl>

<h3>Installation</h3>

<p>

Place the shared library binary in an appropriate location.

Log in to mysql as root or as another user with sufficient privileges, and select any database.

Then, create the function using the following DDL statement:

</p>

<pre>

CREATE FUNCTION sys_eval RETURNS STRING SONAME 'lib_mysqludf_sys.so';

</pre>

<p>

The function will be globally available in all databases.

</p>

<p>

The deinstall the function, run the following statement:

</p>

<pre>

DROP FUNCTION sys_eval;

</pre>

<h3>Examples</h3>

<p>

None yet

</p>

<h3>A Note of Caution</h3>

<p>

Be very careful in deciding whether you need this function.

UDFs are available to all database users - you cannot grant EXECUTE privileges for them.

As the commandstring passed to <code>sys_exec</code> can do pretty much everything,

exposing the function poses a very real security hazard.

</p>

<p>

Even for a benign user, it is possible to accidentally do a lot of damage with it.

The call will be executed with the privileges of the os user that runs MySQL,

so it is entirely feasible to delete MySQL's data directory, or worse.

</p>

<p>

The function is intended for specialized MySQL applications where one needs extended

control over the operating system.

Currently, we do not have UDF's for ftp, email and http,

and this function can be used to implement such functionality in case it is really necessary

(datawarehouse staging areas could be a case in example).

</p>

<p>

You have been warned! If you don't see the hazard, please don't try to find it; just trust me on this.

</p>

<p>

If you do decide to use this library in a production environment, make sure that only specific commands can be run and file access is limited by using <a href="http://www.novell.com/documentation/apparmor/index.html">AppArmor</a>.

</p>

<p>

If you do decide to use this library in a production environment, make sure that only specific commands can be run and file access is limited by using <a href="http://www.novell.com/documentation/apparmor/index.html">AppArmor</a>.

</p>