The two would-be robbers are white, in their early-20s, clean shaven and slim.
One wore a dark-grey hooded top with the hood up and spoke with a Glasgow accent and the other man wore a dark-coloured hooded top and jogging bottoms.
Detective Inspector Ian Hylands said: "These men were determined to rob this shop and were armed with weapons, including a sword, to do so.
"Thankfully the man in the shop was not seriously injured but this could have had terrible consequences. The area was busy at the time with shoppers and to be in possession of a sword in a crowded area is outrageous.
Anyone with information can call local police on 0141 532 5400 or Crimestoppers anonymously on 0800 555 111.