Usage: gnmmanage [--help][--help-general][-q][-quiet][--long-usage]
                 [info]
                 [create [-f <format_name>] [-t_srs <srs_name>] [-dsco <NAME>=<VALUE>]... ]
                 [import <src_dataset_name>] [-l <layer_name>]
                 [connect <gfid_src> <gfid_tgt> <gfid_con> [-c <cost>] [-ic <inv_cost>] [-dir <dir>]]
                 [disconnect <gfid_src> <gfid_tgt> <gfid_con>]
                 [rule <rule_str>]
                 [autoconnect <tolerance>]
                 [delete]
                 [change [-bl <gfid>][-unbl <gfid>][-unblall]]
                 <gnm_name> [<layer> [<layer>]...]

Note: gnmmanage --long-usage for full help.