Script to remove environment variables from list of whitelisted or valid environments to keep. maintain file name called env_to_keep.txt where each line will have environment variable names, each separated by new line.

env_to_keep.txt

BASH
BASH_ALIASES
BASH_ARGC
BASH_ARGV
BASH_CMDS
BASH_COMMAND
BASH_LINENO
BASH_SOURCE
BASH_SUB
BASH_SUBSHELL
BASH_VERSINFO
BASH_VERSION
BASHOPTS
BASHPID
CHOWN_HOME
DEBIAN_FRONTEND
DIRSTACK
GROUPS
HISTCMD
HOME
IFS
LANG
LANGUAGE
LC_ALL
LINENO
LINES
OPTERR
OPTIND
OPTS
OSTYPE
PATH
PIPESTATUS
PPID
PS4
PWD
PYX_DIMENSIONS
PYXTERM_DIMENSIONS
RANDOM
SECONDS
SHELL
SHELLOPTS
SHLVL
TERM
UAGE
UID
_
_SPEC
_SPEC

whitelist_env.sh

#!/bin/sh
# usage: bash whitelist_env.sh env_to_keep.txt

filename=$1  # argument file env_to_keep.txt

# list down all vars
list_of_env_vars=`compgen -v`
echo $list_of_env_vars
echo "Starting to whitelist environments from file $filename"

# going through whitelisted environments and remove whitelisted envs from avaible envs
while read p; do 
      p=" $p "
      list_of_env_vars=`echo $list_of_env_vars | sed "s/$p/ /g"`
done < $filename
echo "End"

echo "below list of envs will be removed."
echo $list_of_env_vars

# removing remaining enviroments 
unset $list_of_env_vars
declare +x $list_of_env_vars