Cannot get example below from docs to work.

If enabled in the INI file G-code has access to the values of INI file entries and HAL pins.

#<_ini[section]name> Returns the value of the corresponding item in the INI file. For example, if the ini file looks like so:

[SETUP]
XPOS = 3.145
YPOS = 2.718
you may refer to the named parameters #<_ini[setup]xpos> and #<_ini[setup]ypos> within G-code.

EXISTS can be used to test for presence of a given ini file variable:

o100 if [EXISTS[#<_ini[setup]xpos>]]
(debug, [setup]xpos exists: #<_ini[setup]xpos>)
o100 else
(debug, [setup]xpos does not exist)
o100 endif

All I get is setup]xpos does not exist.

I setup ini_vars:

[RS274NGC]
PARAMETER_FILE = linuxcnc.var
INI_VARS = 1

Any ideas?

What version of Linuxcnc are you running?

I'm not familiar with that feature, can you post a link to where it is documented?

My first guess is that it is probably case sensitive and will need to match the all caps used in the ini file.

Isn't it the FEATURES that has to be set for _ini?
[RS274NGC]
FEATURES = 4
from the section above the given example in the docs.

LinuxCNC/AXIS version 2.7.15

linuxcnc.org/docs/devel/html/gcode/overv...tml#gcode:parameters
4. HAL pins and INI values

From the docs:
The names are not case sensitive - they are converted to uppercase before consulting the ini file.

It works with FEATURES = 4

I am running vers 2.7.15. Should I be using a later version? What is the easiest way to update?

Depends on how you installed Linuxcnc.

The easiest way is to give some more info.

I installed it years ago, most likely from the linuxcnc install CD.

Any idea if it's Ubuntu or Debian ?
Any idea of which version ?

I can live with using FEATURES= 4 instead of INI_VARS = 1 in the .ini file if updating my version is going to require a major effort