glk_schannel_iterate ()

schanid_t
glk_schannel_iterate (schanid_t chan,
                      glui32 *rockptr);

This function can be used to iterate through the list of all open channels. See Iterating through Opaque Objects.

As that section describes, the order in which channels are returned is arbitrary.

glk_schannel_get_rock ()

glui32
glk_schannel_get_rock (schanid_t chan);

Retrieves the channel's rock value. See Rocks.