How can I list the key groups for GPG?

Question

Say I've setup or defined a key group or a number of key groups. How do I list those groups? How can I determine what keys are members of those groups?

Answer 1

gpg --with-colons --list-config group

From Using the GNU Privacy Guard: GPG Esoteric Options:

--list-config

Display various internal configuration parameters of GnuPG. This option is intended for external programs that call GnuPG to perform tasks, and is thus not generally useful. See the file doc/DETAILS in the source distribution for the details of which configuration items may be listed. --list-config is only usable with --with-colons set.

From the doc/DETAILS file in the source of GPG 1.4.22:

Format of the "--list-config" output
====================================

--list-config outputs information about the GnuPG configuration for
the benefit of frontends or other programs that call GnuPG.  There are
several list-config items, all colon delimited like the rest of the
--with-colons output.  The first field is always "cfg" to indicate
configuration information.  The second field is one of (with
examples):

...

group: the third field contains the name of the group, and the fourth
       field contains the values that the group expands to, separated
       by semicolons.

For example, a group of:
   group mynames = paige 0x12345678 joe patti

would result in:
   cfg:group:mynames:patti;joe;0x12345678;paige