COPY TO File: Using dynamic file name in stored procedure

Hi,

What would it be the correct format for using a variable in a stored procedure that uses COPY TO?

I have the current stored procedure:

CREATE FUNCTION Table_To_File(text) RETURNS void AS $delimeter$

   COPY (SELECT * FROM table_to_xml('table', true, false, '')) TO '$1' WITH CSV QUOTE ' ';

$delimeter$

LANGUAGE SQL;

When I run the stored procedure: psql –d <db name> -c “select Table_To_File(‘some_absolute_file_name’)”;  I get the error that I must use absolute file names.

When I replace TO ‘$1’ with TO ‘/tmp/toto.xml’, the stored procedure runs fine and creates the local file.

I have tried several different ways to escape the $1 variable to no avail.  At best, I get the same error.