File: gnupg.info,  Node: Ephemeral home directories,  Next: The quick key manipulation interface,  Prev: Programmatic use of GnuPG,  Up: Unattended Usage of GPG

4.5.2 Ephemeral home directories
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Sometimes you want to contain effects of some operation, for example you
want to import a key to inspect it, but you do not want this key to be
added to your keyring.  In earlier versions of GnuPG, it was possible to
specify alternate keyring files for both public and secret keys.  In
modern GnuPG versions, however, we changed how secret keys are stored in
order to better protect secret key material, and it was not possible to
preserve this interface.

   The preferred way to do this is to use ephemeral home directories.
This technique works across all versions of GnuPG.

   Create a temporary directory, create (or copy) a configuration that
meets your needs, make 'gpg' use this directory either using the
environment variable GNUPGHOME, or the option '--homedir'.  GPGME
supports this too on a per-context basis, by modifying the engine info
of contexts.  Now execute whatever operation you like, import and export
key material as necessary.  Once finished, you can delete the directory.
All GnuPG backend services that were started will detect this and shut
down.