For the life of me I cannot imagine why one would want to do THAT!  However:

If you just want the schema:
dbschema -d mydatabasename -ss mydatabasename.sql

To get the data also:
dbexport -d mydatabasename -o . -ss

Which will create a subdirectory in '.' named mydatabasename.exp containing a
schema enhanced with the names and description of the unload files and a
bunch of delimited data unload files.

You'll have to edit the schema file to alter Informix-isms into MySQL-isms
and I do not know how you'll reload the data, but there it is.

Art S. Kagel

dbschema -d dbname dbname.sql

That will put a complete schema in the file dbname.sql -- you will have
to edit it for use with MySQL, particularly if you have views, stored
procedures and triggers, but also some basic syntax (MySQL will let you
know what you need to change).