translating other g-code formats to ngc

I found that people have problems converting g-codes to ngc format. Those who answer in the forums say: "change the txt to "ngc and it will work" or "it's just a text file tha linux cnc will read. It's not that simple, I tried and it just doesn't work.

I am trying to understand what linux cnc looks for in the g-code file so I won't have this problem in the future.

I was wondering what changes do I need to make to this 4-axis g-code (besides giving it "ngc" extension) to make it work with linux cnc:

%
N1 G00 G17 G90
N2 G40 G49 G80
N3 G70
N4 S5000 M3
N5 G01 X1.6307 Y0. F5.9
N6 Z0.084
N7 A0. F5.9
N8 Z-0.1969 A0.
N9 X1.6484 A-360. F7.9
N10 X1.6662 A0.
N11 X1.6839 A-360.
N12 X1.7016 A0.
N13 X1.7193 A-360.
....
....
....
N1703 Z-0.4398 A-151.
N1704 Z-0.4375 A-112.5
N1705 Z-0.4373 A-74.3
N1706 Z-0.4394 A-38.1
N1707 Z-0.4426 A0.
N1708 Z0.084 A0. F5.9
N1709 M30
%

Hope someone can explain it to me.
Thanks

you need to look and learn gcode , in the majority of cases it is all the same .. however every vendor can have there own quirks , this is where when gcode if produced , a Postprocessor
comes in , there are tutorials in the documentation section , and all over the internet , a good book to obtain is CNC Programming Handbook by Peter Smid ,
understanding each gcode is the key to good programming , either to understand what a cam program has produced , or to hand edit previous code done for another machine

Also another good tutorial gnipsel.com/linuxcnc/g-code/index.html

but to look at your example and tear it apart line by line

% is realy just a start and end marker , mostly used on older machines so not needed but does no harm
N1 etc is line numbering , linuxcnc does not use line numbers so they can go
now comes an initialisation sequence G00 G17 G90 G40 G49
specific gcodes such as G80 and G70 are profile and finishing cycle commands which may or may not be understood by linuxcnc

other commands S = Spindle F = feedrate M3 = start M30 = end program
so you should now be able to split up and understand the code better , the majority are universal across all , but others are specific to the machine it's coded for , so splitting up has shown that discounting some has left you with 2 G80 and G70 which are specific to which machine this has been produced for , so you may either delete them or change to suit

a quick look here linuxcnc.org/docs/html/gcode.html
shows that G80 and G70 are not supported ..

this is just a brief outline , there are many other parts to your learning curve , but all are not difficult to understand , once you start to break it down

gcode is mostly transferable across machines , but every manufacturer has it's own tweaks , but most code produced can be hand edited
with care and understanding , but never think that code can just be ran blind always test for the unexpected first with a dry run ,,

linuxcnc is based on Fanuc code which is mostly universal so your chances of success are greater
it's when you get into machine specifics of things as loops and finishing or threading cycle shortcuts etc you will be most vunerable to making mistakes .

Thank you very much! This is exactly the kind of answer I was looking for. I put the semicolon before N3 line and changed the txt extension to ngc. Looks like it will work fine.