If you write build scripts that must remain portable to old machines with old implementations that you cannot ensure have been upgraded or modified to provide a recent ASDF, you may have to install the file asdf.lisp somewhere and load it with:
The single file asdf.lisp is all you normally need to use ASDF.
You can extract this file from latest release tarball on the ASDF website. If you are daring and willing to report bugs, you can get the latest and greatest version of ASDF from its git repository. See Getting the latest version.
For scripts that try to use ASDF simply via
require at first, and
make heroic attempts to load it the hard way if at first they don’t succeed,
see tools/load-asdf.lisp distributed with the ASDF source repository,
or the code of