Mr Wilson, 44, originally from Newcastle upon Tyne, lived in Willowbrae, Edinburgh, with his wife Diane and four children aged between 4 and 16.
Mr McGarry, 46, a Canadian who also lived in Edinburgh, was married with three teenage children.
Both men were working as pipe coaters in an oil refinery when the attack took place in the early hours. They had been in Algeria for five weeks.
A workmate, Thomas Ramsay, also from Edinburgh, who returned from the site a few days ago, said last night: "I've just lost five friends. I'm told they just opened fire on everyone who was there and sprayed them with bullets. It sounds as if they had no chance."
British Pipe Coaters is a subsidiary of Bredero Price of Berkshire. They were carrying out a contract in Algeria for Bechtel.
Yesterday the Edinburgh office was closed as a mark of respect. Staff who turned up for work were sent home.
A Foreign Office spokesman said: "A civil war has been going on in Algeria for the last five years and we advised all British nationals to leave months ago."