even better....
of course you could do as I mention....
but that'd mean you having to go moving left to right, down bellow the horizontal scroll bar of the window, to keep it scroll-selecting... But that would be REALLY tiring...many minutes till u have a 50,000 tris mesh fully selected...
Instead, and only in case (which I recommend strongly for 3d) u have a 3 mouse button mouse , being third the same wheel, that besides allowing wheel zoom in most softwares, is clickable, and as that, works as an standard clickable middle mouse....The u can do much quicker this way :
-maximize the listener window.
-select the two first lines for example of the whole thing, up there. never release left button.
-with cursor still there, click MIDDLE mouse(not keep pressed). If ur os, or mouse driver (I think most windows will adpat it automatically, but in other mouses would be needed that u installed well its driver) is wel setup, there's will appear that up-down arrows with a circle in the center...I think newer oses does this automatically...is for scrolling pages. As u'll know, if u now move down a bit the mouse, it starts to scroll down.And as u'll also know, the more far downward u get, the quicker it scroll (usually getting to quick to control,lol) .Well, the key here is...do with window maximized as I said, and without never clicking again on middle,left mouse still pressed, carry the cursor to the lower part of ur screen...so, it considers the highest distance possible and scrolls down really fast.
(Still, took me like a miniute I think to have a 50k tris obj text selected...remember... I have left allways pressed. If u click middle again, it'll cancel all.)
-Ok, once at the end, the double arrowed icon still there, u'll see, as when scrolling uber fast, that looks like nothing was selected...nope, it has been selecting, is just too quick to refresh...yet not clicking middle (actually u never click middle again) , but (of course!) left mouse yet pressed, you move mouse over the final line (it says something like "end") and now u can breath again, as u see how it got black, selected, till there...ok, make it cover till last line moving ur mouse, and like in first explanation, without releasing left button, make a right click press (but a click, I mean, releasing the RIGHT after the click!!) and so, u'll see context floating menu ,appear with typical options, choose "copy". U're done
-Now go to whatever u use as notepad...if is limited in 64ks, like old notepad were, then use worpad or the like.Paste it . Save as TEXT file (ascii, ansi, plain text, u know the concept

) . Then go to the folder, and rename as whatever the name with *.obj extension. Finish.
This way is much quicker.
A 6k tris level gets exported in little time. And a 50k , in a reasonable time, I mean, it makes u be there some minute hearing an music or something...
Of course, if u control how things go with ur mouse driver and is one of those over powered drivers, u may change the scroll speed in its control panel, so u could set it to a crazy value...anyway, i don't use even that funtion, is never good fo rme, i use just the wheel to read text...
Also, I recommend equally Blender, as is also fully open source and quite powerful, though not so extremely good as max or gmax, for its greater splines and and snap functions, and other accurate modelling features.
-besides some people don't find their way in Blender-
But for me are two very good options.