tabcmd is a telnet-type tool for interacting with the server; it cannot be used or be called by way of url.
If you are using Tableau Server, then you could use a scheduling tool such as SSIS or Jenkins or even Windows scheduler (on a server box) to execute a batch file that has the command to export or print all or the selected dashboards from your workbook and then, to interact with your mail program to mail to your selected recipients, or, to simply place it in a new folder.
Keep in mind, you will need to do some batch programming for this to work.
This is a list of tabcmd commands: tabcmd Commands - Tableau
Although tabcmd has now been superseded by TSM
Is there any other way to download all the sheets in a single click through dashboard?
It looks like your only option would be to download as a pdf as this gives you the options to select one, many or all sheets, and provides options for scaling and orientation too. And, the pdf will zoom to its highest without loss of quality.