Msi Environment

Set Environment Variables.

Documentation

Environment table

https://docs.microsoft.com/en-us/windows/win32/msi/environment-table

Overview

Table Columns
Environment	TESTVAR	primary key/handle
Name	*=-TEST	name of the environment-variable (localized)
Value	[~];1	value of environment variable.
Component_	TESTVAR_ENV	primary-key of envvar's component.

Python Example

# Add Component to Feature (so it is installed)
featcomp_data = [('Everything', 'Foo_Reg')]
msilib.add_data(db, 'FeatureComponents', featcomp_data)

# Create Component for RegistryKey
comp_data = [('Foo_Reg',          # Component
              msilib.gen_uuid(),  # ComponentId
              'TARGETDIR',        # Directory_
              2,                  # Attributes
              None,               # Condition
              None)]              # KeyPath
msilib.add_data(db, 'Component', comp_data)

# Define RegistryKey
env_data = [('Foo_Reg',           # Environment
             '=-Foo',             # Name  (installed/uninstalled)
             'Bar',               # Value
             'Foo_Reg')]          # Component_
msilib.add_data(db, 'Environment', env_data)

User/System Variable

Environment variables are user variables by default.
If you desire a system-wide variable, use the prefix * in the column Name.
This precedes the prefix to designate add/remove variable, if present.

*SYSTEM_VARIABLE
USER_VARIABLE

Add/Remove Variable

Adding/Removing variables is indicated with a Name column prefix.

=VARIABLE  # create if not exist, set during install regardless of whether or not it already exists
+VARIABLE  # create if not exist, only set if does not already exist
-VARIABLE  # remove variable when application is uninstalled
!VARIABLE  # remove variable at install

# these can be combined
=-VARIABLE  # set on install, removed on uninstall

Append/Prepend Value

By default variables are replaced.
To append/prepend use [~]; at the start or end of the Value column.

VALUE      # replace value (depends on 'Name' col prefix)
[~];VALUE  # append value
VALUE;[~]  # prepend value