extconf.rb

frozen_string_literal: false configure option:

--with-dbm-type=COMMA-SEPARATED-NDBM-TYPES

ndbm type:

libc        ndbm compatible library in libc.
db          Berkeley DB (libdb)
db2         Berkeley DB (libdb2)
db1         Berkeley DB (libdb1)
db5         Berkeley DB (libdb5)
db4         Berkeley DB (libdb4)
db3         Berkeley DB (libdb3)
gdbm_compat GDBM since 1.8.1 (libgdbm_compat)
gdbm        GDBM until 1.8.0 (libgdbm)
qdbm        QDBM (libqdbm)
ndbm        Some legacy OS may have libndbm.