OK sudo strace -- swaymsg --socket $SWAYSOCK -t get_inputs 2> swaymsg_getinputs_withswaysock.log
44 socket(AF_UNIX, SOCK_STREAM, 0) = 3
45 connect(3, {sa_family=AF_UNIX, sun_path="/run/user/1000/sway-ipc.1000.1324.sock"}, 110) = 0
46 setsockopt(3, SOL_SOCKET, SO_RCVTIMEO_OLD, "\3\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16) = 0
47 write(3, "i3-ipc\0\0\0\0d\0\0\0", 14) = 14
48 write(3, "", 0) = 0
49 recvfrom(3, "i3-ipc\31\26\0\0d\0\0\0", 14, 0, NULL, NULL) = 14
50 recvfrom(3, "[ { \"identifier\": \"0:0:Eee_PC_WM"..., 5657, 0, NULL, NULL) = 5657