multi Turtles saving location files

I am currently working on a program that has my turtles saving their current location to a file. Whats the code to have all the turtles access the same file

file = fs.open("abc.txt" , "r")

opens the file for the specific turtle.
isn't there something like

file = fs.open("c:\yada\yada\yada\abc.txt" , "r")

so all the turtles can access the same file?

No.
Each turtle is a separate computer, so you can't access files on other one. However, you could create some server that gives access to files through rednet.