MDB provides a set of built-in dcmds that are always defined. Some
of these dcmds are applicable only to certain targets: if a dcmd is
not applicable to the current target, it fails and prints a message indicating
“command is not supported by current target”.
In many cases, MDB provides a mnemonic equivalent (::identifier) for the legacy adb(1)
dcmd names. For example, ::quit is provided as the equivalent of $q. Programmers who
are experienced with adb(1) or who appreciate brevity or arcana might prefer the
$ or : forms of the built-ins. Programmers who are new to MDB
might prefer the more verbose :: form. The built-ins are shown in
alphabetical order. If a $ or : form has a ::identifier equivalent, it
is shown under the ::identifier form.