Is there a command on Mac can show the disk IO input and output stats?
The closest thing to getting IO r/w info is iotop command, which comes with all Mac OS (see disk_r and disk_w).

$ sudo iotop
2019 Jul 15 22:39:17,  load: 1.19,  disk_r:      0 KB,  disk_w:    628 KB

  UID    PID   PPID CMD              DEVICE  MAJ MIN D            BYTES
    0      1      0 launchd          ??        1   2 W           643072
    0      0      0                  ??        1   2             649216


If you are running on Mac OSX 10.10 (El Capitan) or later, then you need to first disable the SIP (System Integration Protection) for dtrace in order to run iotop because iotop uses dtrace.  For older OSX, you can ignore the following steps.

To disable SIP for dtrace (and iotop) for Mac OSX 10.10 and above:


Turn on or Restart your Mac
As the Mac is turning on, hold down Command-R to boot into Recovery Mode
Open terminal and type csrutil disable (this is a temporary step)
type csrutil enable --without dtrace. (It re-enables SIP except for dtrace)
Reboot your Mac


Now you can run iotop and dtrace.  


If you want to restore SIP to its original state, and to prevent dtrace from running, reboot into Recovery Mode and in terminal, type csrutil enable and reboot.