[Rd] The Environment variables settings in bin/R, why do they ignore environment variables of the same name?

[Saptarshi Guha]

Hello,

In installation/R/bin/R i notice

1. R_HOME_DIR is hard coded e.g.
R_HOME_DIR=/usr/local/lib64/R

2. It ignores R_HOME_DIR

echo "WARNING: ignoring environment value of R_HOME"

3. R_SHARE_DIR, R_INCLUDE_DIR and R_DOC_DIR are also hard coded.

Is there a reason why these  settings do not read the values from the
environment variables of the same name (assuming they exist) and
defaulting to these hard coded values in case they dont?

Regards
Saptarshi