refrenvz.sh

#!/bin/zsh

# author: Badr Elmers 2021-2023
# description: RefrEnv = refresh environment. for ZSH of Cygwin/Msys2/GitBash
# version: 1.0
# https://github.com/badrelmers/RefrEnv
# https://stackoverflow.com/questions/171588/is-there-a-command-to-refresh-environment-variables-from-the-command-prompt-in-w

###########################################################################################

datenow=$(date +%Y%m%d_%H%M%S)
RefrEnv_Temp_Dir="${TEMP}/RefrEnvBash_${datenow}_${RANDOM}${RANDOM}"

# use subshell so we do not pollute the parent script
(

# ### USAGE ################################################################
RefrEnv_help(){
printf '%s' '
NAME
    RefrEnv - Refresh the Environment for Zsh

SYNOPSIS
    source refrenvz.sh
    
DESCRIPTION
    By default with no arguments, this script will do a full 
    refresh (refresh all non critical variables*, and refresh the PATH).

    you can use the following variables to change some behaviours:
    
    RefrEnv_StrictRefresh=yes   Strict mode (secure refresh). this prevent 
                                refreshing a variable if it is already defined  
                                in the actual zsh session. 
                                The PATH will be refreshed.
                                
    RefrEnv_ResetPath=yes       Reset the actual PATH inside zsh, then refresh
                                it with a new PATH. This will delete any PATH 
                                added by the script who called RefrEnv. It is 
                                equivalent to running a new zsh session.

    RefrEnv_debug=yes           Debug what this script do. The folder containing
                                the files used to set the variables will be
                                open, then see _NewEnv.sh, this is the file
                                which run inside your script to setup the new
                                variables, you can also revise the intermediate
                                .txt files.
                              
    RefrEnv_help=yes            Print the help.

    you can also put this script in windows\systems32 or another place in your 
    $PATH then call it from an interactive console by writing: source refrenv.sh

    *critical variables: are variables which belong to zsh or windows and should
    not be refreshed normally like:
    - windows vars:
        ALLUSERSPROFILE APPDATA CommonProgramFiles CommonProgramFiles(x86)
        CommonProgramW6432 COMPUTERNAME ComSpec HOMEDRIVE HOMEPATH LOCALAPPDATA 
        LOGONSERVER NUMBER_OF_PROCESSORS OS PATHEXT PROCESSOR_ARCHITECTURE 
        PROCESSOR_ARCHITEW6432 PROCESSOR_IDENTIFIER PROCESSOR_LEVEL 
        PROCESSOR_REVISION ProgramData ProgramFiles ProgramFiles(x86) 
        ProgramW6432 PUBLIC SystemDrive SystemRoot TEMP TMP USERDOMAIN 
        USERDOMAIN_ROAMINGPROFILE USERNAME USERPROFILE windir SESSIONNAME
    - bash vars:
        BASH BASHOPTS BASHPID BASH_ALIASES BASH_ARGC BASH_ARGV BASH_CMDS 
        BASH_COMMAND BASH_COMPLETION_VERSINFO BASH_LINENO BASH_REMATCH 
        BASH_SOURCE BASH_SUBSHELL BASH_VERSINFO BASH_VERSION COLUMNS 
        COMP_WORDBREAKS CYGWIN CYG_SYS_BASHRC DIRSTACK EUID EXECIGNORE 
        FUNCNAME GROUPS HISTCMD HISTCONTROL HISTFILE HISTFILESIZE HISTSIZE 
        HISTTIMEFORMAT HOME HOSTNAME HOSTTYPE IFS INFOPATH LANG LC_ALL 
        LC_COLLATE LC_CTYPE LC_MESSAGES LC_MONETARY LC_NUMERIC LC_TIME LINENO 
        LINES MACHTYPE MAILCHECK OLDPWD OPTERR OPTIND ORIGINAL_PATH OSTYPE PATH 
        PIPESTATUS POSIXLY_CORRECT PPID PRINTER PROFILEREAD PROMPT_COMMAND PS0 
        PS1 PS2 PS3 PS4 PWD RANDOM SECONDS SHELL SHELLOPTS SHLVL SSH_ASKPASS 
        TERM TERM_PROGRAM TERM_PROGRAM_VERSION TZ UID USER _backup_glob 
        CHILD_MAX BASH_COMPAT FUNCNEST COMP_TYPE COMP_KEY READLINE_LINE_BUFFER 
        READLINE_POINT PROMPT_DIRTRIM BASH_EXECUTION_STRING COPROC_PID COPROC 
        GLOBIGNORE HISTIGNORE SRANDOM READLINE_MARK EPOCHSECONDS EPOCHREALTIME 
        BASH_ARGV0 COMPREPLY COMP_CWORD COMP_LINE COMP_POINT COMP_WORDS EMACS 
        FCEDIT FIGNORE HOSTFILE IGNOREEOF INPUTRC INSIDE_EMACS MAPFILE 
        READLINE_LINE REPLY TIMEFORMAT TMOUT TMPDIR histchars
    - zsh vars: 
        ARGC ARGV0 BAUD BUFFER BUFFERLINES CDPATH COLUMNS CONTEXT CORRECT_IGNORE
        CORRECT_IGNORE_FILE CPUTYPE CURRENT CURSOR CUTBUFFER DIRSTACKSIZE EDITOR
        EGID ENV EPOCHREALTIME EPOCHSECONDS ERRNO EUID FCEDIT FIGNORE FPATH 
        FUNCNEST GID HELPDIR HISTCHARS HISTCMD HISTCONTROL HISTFILE HISTNO 
        HISTORY_IGNORE HISTSIZE HOME HOST IFS IPREFIX ISEARCHMATCH_ACTIVE 
        ISEARCHMATCH_END ISEARCHMATCH_START ISUFFIX KEYBOARD_HACK KEYTIMEOUT 
        LINENO LINES LISTMAX LOGCHECK MACHTYPE MAILCHECK MAILPATH MANPATH 
        MODULE_PATH NULLCMD OPTARG OPTIND OSTYPE PATH PPID PROFILEREAD PROMPT2 
        PROMPT3 PROMPT4 PS2 PS3 PS4 PSVAR RANDOM READNULLCMD SAVEHIST SECONDS 
        SHLVL SPROMPT TIMEFMT TMPPREFIX TRY_BLOCK_ERROR TRY_BLOCK_INTERRUPT TTY 
        TTYIDLE UID USERNAME VENDOR WATCH WATCHFMT WORDCHARS ZLE_LINE_ABORTED 
        ZSH_ARGZERO ZSH_EVAL_CONTEXT ZSH_NAME ZSH_PATCHLEVEL ZSH_SUBSHELL 
        ZSH_VERSION aliases all_quotes argv bg bg_bold bg_no_bold bold_color 
        builtins cdpath chpwd_functions color colour commands comppostfuncs 
        compprefuncs compstate context dirstack dis_aliases dis_builtins 
        dis_functions dis_functions_source dis_galiases dis_patchars 
        dis_reswords dis_saliases epochtime errnos exact exact_string expl fg 
        fg_bold fg_no_bold fignore fpath funcfiletrace funcsourcetrace 
        funcstack functions functions_source functrace galiases histchars 
        history historywords ignored incarg insert insert_positions jobdirs 
        jobstates jobtexts keymaps mailpath manpath module_path modules 
        nameddirs options parameters patchars path pipestatus prompt psvar 
        reset_color reswords saliases signals status termcap terminfo userdirs 
        usergroups watch widgets zle_bracketed_paste zsh_eval_context 
        zsh_scheduled_events

    ### INFO #################################################################
     This script reload environment variables inside zsh every time you want 
     environment changes to propagate, so you do not need to restart zsh after 
     setting a new variable with setx or when installing new apps which add new 
     variables ...etc

     for PATH: this script append the new paths to the old path of the parent 
     script which called this script; its better than overwriting the old path; 
     otherwise it will delete any newly added path by the parent script. if you 
     need to reset the PATH use RefrEnv_ResetPath=yes

     ________
     windows recreate the path using three places at least:
     the User namespace:    HKCU\Environment
     the System namespace:  HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
     the Session namespace: HKCU\Volatile Environment
     This script will merge all the three and remove any duplicates. this is 
     what windows do by default too

     there is this too which cmd seems to read when first running, but it 
     contains only TEMP and TMP,so this script will not use it
     HKEY_USERS\.DEFAULT\Environment

     ________
     RefrEnv support the so called zsh Strict Mode like: 
     "set -eEu -o pipefail ; shopt -s inherit_errexit" , you can use the Strict 
     Mode safely in your parent script without worry.

'
}

### TESTING #################################################################
# To test this script with extreme cases do
    # :: Set a bad variable
    # add a var in reg HKCU\Environment as the following, and see that echo is not executed.
    # so save this in reg:
    # all 32 characters: & % ' ( ) ~ + @ # $ { } [ ] ; , ` ! ^ | > < \ / " : ? * = . - _ & echo baaaad
    # and this:
    # (^.*)(Form Product=")([^"]*") FormType="[^"]*" FormID="([0-9][0-9]*)".*$
    # and use 'set' to print those variables and see if they are saved without change
    
    
# invalid characters (illegal characters in file names) in Windows using NTFS
# \ / : * ? "  < > |  and ^ in FAT 



###############################################################################################
###############################################################################################
###############################################################################################

refrenv_main(){
    local runme=yes
    local i=""
    
    if [[ ${RefrEnv_StrictRefresh:-} == yes ]] ; then
        local strict_txt=' - (Strict refresh)'
    fi
    if [[ ${RefrEnv_ResetPath:-} == yes ]] ; then
        local ResetPath_txt=' - (Reset Path)'
    fi
    if [[ ${RefrEnv_debug:-} == yes ]] ; then
        local debug_txt=' - (Debug enabled)'
    fi
    if [[ ${RefrEnv_help:-} == yes ]] ; then
        RefrEnv_help
        local runme=no
    fi

    
    if [[ "${runme:-}" = "yes" ]] ; then
        echo "RefrEnv - Refresh the Environment for Zsh${strict_txt:-}${ResetPath_txt:-}${debug_txt:-}"
        
        rm -rf "${RefrEnv_Temp_Dir}" || true
        mkdir -p "${RefrEnv_Temp_Dir}"

        getNewlyAddedVars '/HKLM/System/CurrentControlSet/Control/Session Manager/Environment'
        getNewlyAddedVars '/HKCU/Environment'
        getNewlyAddedVars '/HKCU/Volatile Environment'
        getNewPATHS
    fi
    
    # unset all the functions we used in this script so we do not pollute the parent script
    # unset -f _common_functions echocolorsV3 INFOC WARNC ERRORC HIDEC INFO2C INFO3C INFO4C INFOCB WARNCB ERRORCB HIDECB INFO2CB INFO3CB INFO4CB ENDC ENDCln _trap_V5 error_handler 
    unset -f RefrEnv_help refrenv_main getNewlyAddedVars getNewPATHS ExpandEnvironmentStrings
    # zsh show this error when we call help : unset:34: no such hash table element: _safe_vars ; this is because _safe_vars was never set up when we call help because it s inside getNewlyAddedVars which zsh seems do not add it to the environment variable if we do not run getNewlyAddedVars
    if [[ "${runme:-}" = "yes" ]] ; then
        unset -f _safe_vars
    fi
}

####################################################################

getNewlyAddedVars(){ 
    # get the newly added variables from registry which are not defined right now in zsh
    local regPath="$1"

    local IFSorg="$IFS"
    IFS=$'\n'
    
    # print all reg variables and remove critical ones, i created the list using: the windows registry, set declare compgen printenv env and the bash changelog : https://github.com/bminor/bash/blob/8868edaf2250e09c4e9a1c75ffe3274f28f38581/NEWS so it is up to bash-5.1
    # i used also the manual
    # https://web.archive.org/web/20210507012307/https://gnu.org/software/bash/manual/html_node/Bash-Variables.html
    # i will not add :
    # BASH_LOADABLES_PATH
    # ENV and BASH_ENV
    # BASH_XTRACEFD

    # --list is important otherwise the reg subdirectories are printed , volatile environment for example have a folder/subkey called 1 and it is printed if i do not use --list
    
    # the bash man page defines the export syntax as:
    # export [-fn] [name[=word]] ...
    # and defines a "name" as:
    # name   A  word  consisting  only  of alphanumeric characters and under-
    #        scores, and beginning with an alphabetic character or an  under-
    #        score.  Also referred to as an identifier.
    # so we need to exclude anything that does not follow those rules, otherwise we get errors like in https://github.com/badrelmers/RefrEnv/issues/2 , because windows allow to set vars like "z.z" , "z-z" and "z z" which bash and zsh will not accept https://unix.stackexchange.com/questions/93532/exporting-a-variable-with-dot-in-it . a simple  grep -e '^[a-zA-Z_][a-zA-Z0-9_]*$' solve this
    
    # i created the zsh builtin variables by combining the result of this two:
    # https://zsh.sourceforge.io/Doc/Release/Variables-Index.html
    # comm -23 <(typeset -m | cut -d= -f1 | sort) <(export | cut -d= -f1 | sort)

    # TODO: remove the bash builtins vars if not needed here, the first list before the space is the windows list, the second list is the bash list , and the rest is the zsh list
    local regresult
    regresult=$(regtool list --list "${regPath}")
    regresult=$(printf '%s' "${regresult}" | grep -e '^[a-zA-Z_][a-zA-Z0-9_]*$' | grep -i -v -e '^ALLUSERSPROFILE$' -e '^APPDATA$' -e '^CommonProgramFiles$' -e '^CommonProgramFiles(x86)$' -e '^CommonProgramW6432$' -e '^COMPUTERNAME$' -e '^ComSpec$' -e '^HOMEDRIVE$' -e '^HOMEPATH$' -e '^LOCALAPPDATA$' -e '^LOGONSERVER$' -e '^NUMBER_OF_PROCESSORS$' -e '^OS$' -e '^PATHEXT$' -e '^PROCESSOR_ARCHITECTURE$' -e '^PROCESSOR_ARCHITEW6432$' -e '^PROCESSOR_IDENTIFIER$' -e '^PROCESSOR_LEVEL$' -e '^PROCESSOR_REVISION$' -e '^ProgramData$' -e '^ProgramFiles$' -e '^ProgramFiles(x86)$' -e '^ProgramW6432$' -e '^PUBLIC$' -e '^SystemDrive$' -e '^SystemRoot$' -e '^TEMP$' -e '^TMP$' -e '^USERDOMAIN$' -e '^USERDOMAIN_ROAMINGPROFILE$' -e '^USERNAME$' -e '^USERPROFILE$' -e '^windir$' -e '^SESSIONNAME$'                     -e '^BASH$' -e '^BASHOPTS$' -e '^BASHPID$' -e '^BASH_ALIASES$' -e '^BASH_ARGC$' -e '^BASH_ARGV$' -e '^BASH_CMDS$' -e '^BASH_COMMAND$' -e '^BASH_COMPLETION_VERSINFO$' -e '^BASH_LINENO$' -e '^BASH_REMATCH$' -e '^BASH_SOURCE$' -e '^BASH_SUBSHELL$' -e '^BASH_VERSINFO$' -e '^BASH_VERSION$' -e '^COLUMNS$' -e '^COMP_WORDBREAKS$' -e '^CYGWIN$' -e '^CYG_SYS_BASHRC$' -e '^DIRSTACK$' -e '^EUID$' -e '^EXECIGNORE$' -e '^FUNCNAME$' -e '^GROUPS$' -e '^HISTCMD$' -e '^HISTCONTROL$' -e '^HISTFILE$' -e '^HISTFILESIZE$' -e '^HISTSIZE$' -e '^HISTTIMEFORMAT$' -e '^HOME$' -e '^HOSTNAME$' -e '^HOSTTYPE$' -e '^IFS$' -e '^INFOPATH$' -e '^LANG$' -e '^LC_ALL$' -e '^LC_COLLATE$' -e '^LC_CTYPE$' -e '^LC_MESSAGES$' -e '^LC_MONETARY$' -e '^LC_NUMERIC$' -e '^LC_TIME$' -e '^LINENO$' -e '^LINES$' -e '^MACHTYPE$' -e '^MAILCHECK$' -e '^OLDPWD$' -e '^OPTERR$' -e '^OPTIND$' -e '^ORIGINAL_PATH$' -e '^OSTYPE$' -e '^PATH$' -e '^PIPESTATUS$' -e '^POSIXLY_CORRECT$' -e '^PPID$' -e '^PRINTER$' -e '^PROFILEREAD$' -e '^PROMPT_COMMAND$' -e '^PS0$' -e '^PS1$' -e '^PS2$' -e '^PS3$' -e '^PS4$' -e '^PWD$' -e '^RANDOM$' -e '^SECONDS$' -e '^SHELL$' -e '^SHELLOPTS$' -e '^SHLVL$' -e '^SSH_ASKPASS$' -e '^TERM$' -e '^TERM_PROGRAM$' -e '^TERM_PROGRAM_VERSION$' -e '^TZ$' -e '^UID$' -e '^USER$' -e '^_backup_glob$'           -e '^CHILD_MAX$' -e '^BASH_COMPAT$' -e '^FUNCNEST$' -e '^COMP_TYPE$' -e '^COMP_KEY$' -e '^READLINE_LINE_BUFFER$' -e '^READLINE_POINT$' -e '^PROMPT_DIRTRIM$' -e '^BASH_EXECUTION_STRING$' -e '^COPROC_PID$' -e '^COPROC$' -e '^GLOBIGNORE$' -e '^HISTIGNORE$' -e '^SRANDOM$' -e '^READLINE_MARK$' -e '^EPOCHSECONDS$' -e '^EPOCHREALTIME$' -e '^BASH_ARGV0$' -e '^COMPREPLY$' -e '^COMP_CWORD$' -e '^COMP_LINE$' -e '^COMP_POINT$' -e '^COMP_WORDS$' -e '^EMACS$' -e '^FCEDIT$' -e '^FIGNORE$' -e '^HOSTFILE$' -e '^IGNOREEOF$' -e '^INPUTRC$' -e '^INSIDE_EMACS$' -e '^MAPFILE$' -e '^READLINE_LINE$' -e '^REPLY$' -e '^TIMEFORMAT$' -e '^TMOUT$' -e '^TMPDIR$' -e '^histchars$'                     -e '^ARGC$' -e '^ARGV0$' -e '^BAUD$' -e '^BUFFER$' -e '^BUFFERLINES$' -e '^CDPATH$' -e '^COLUMNS$' -e '^CONTEXT$' -e '^CORRECT_IGNORE$' -e '^CORRECT_IGNORE_FILE$' -e '^CPUTYPE$' -e '^CURRENT$' -e '^CURSOR$' -e '^CUTBUFFER$' -e '^DIRSTACKSIZE$' -e '^EDITOR$' -e '^EGID$' -e '^ENV$' -e '^EPOCHREALTIME$' -e '^EPOCHSECONDS$' -e '^ERRNO$' -e '^EUID$' -e '^FCEDIT$' -e '^FIGNORE$' -e '^FPATH$' -e '^FUNCNEST$' -e '^GID$' -e '^HELPDIR$' -e '^HISTCHARS$' -e '^HISTCMD$' -e '^HISTCONTROL$' -e '^HISTFILE$' -e '^HISTNO$' -e '^HISTORY_IGNORE$' -e '^HISTSIZE$' -e '^HOME$' -e '^HOST$' -e '^IFS$' -e '^IPREFIX$' -e '^ISEARCHMATCH_ACTIVE$' -e '^ISEARCHMATCH_END$' -e '^ISEARCHMATCH_START$' -e '^ISUFFIX$' -e '^KEYBOARD_HACK$' -e '^KEYTIMEOUT$' -e '^LINENO$' -e '^LINES$' -e '^LISTMAX$' -e '^LOGCHECK$' -e '^MACHTYPE$' -e '^MAILCHECK$' -e '^MAILPATH$' -e '^MANPATH$' -e '^MODULE_PATH$' -e '^NULLCMD$' -e '^OPTARG$' -e '^OPTIND$' -e '^OSTYPE$' -e '^PATH$' -e '^PPID$' -e '^PROFILEREAD$' -e '^PROMPT2$' -e '^PROMPT3$' -e '^PROMPT4$' -e '^PS2$' -e '^PS3$' -e '^PS4$' -e '^PSVAR$' -e '^RANDOM$' -e '^READNULLCMD$' -e '^SAVEHIST$' -e '^SECONDS$' -e '^SHLVL$' -e '^SPROMPT$' -e '^TIMEFMT$' -e '^TMPPREFIX$' -e '^TRY_BLOCK_ERROR$' -e '^TRY_BLOCK_INTERRUPT$' -e '^TTY$' -e '^TTYIDLE$' -e '^UID$' -e '^USERNAME$' -e '^VENDOR$' -e '^WATCH$' -e '^WATCHFMT$' -e '^WORDCHARS$' -e '^ZLE_LINE_ABORTED$' -e '^ZSH_ARGZERO$' -e '^ZSH_EVAL_CONTEXT$' -e '^ZSH_NAME$' -e '^ZSH_PATCHLEVEL$' -e '^ZSH_SUBSHELL$' -e '^ZSH_VERSION$' -e '^aliases$' -e '^all_quotes$' -e '^argv$' -e '^bg$' -e '^bg_bold$' -e '^bg_no_bold$' -e '^bold_color$' -e '^builtins$' -e '^cdpath$' -e '^chpwd_functions$' -e '^color$' -e '^colour$' -e '^commands$' -e '^comppostfuncs$' -e '^compprefuncs$' -e '^compstate$' -e '^context$' -e '^dirstack$' -e '^dis_aliases$' -e '^dis_builtins$' -e '^dis_functions$' -e '^dis_functions_source$' -e '^dis_galiases$' -e '^dis_patchars$' -e '^dis_reswords$' -e '^dis_saliases$' -e '^epochtime$' -e '^errnos$' -e '^exact$' -e '^exact_string$' -e '^expl$' -e '^fg$' -e '^fg_bold$' -e '^fg_no_bold$' -e '^fignore$' -e '^fpath$' -e '^funcfiletrace$' -e '^funcsourcetrace$' -e '^funcstack$' -e '^functions$' -e '^functions_source$' -e '^functrace$' -e '^galiases$' -e '^histchars$' -e '^history$' -e '^historywords$' -e '^ignored$' -e '^incarg$' -e '^insert$' -e '^insert_positions$' -e '^jobdirs$' -e '^jobstates$' -e '^jobtexts$' -e '^keymaps$' -e '^mailpath$' -e '^manpath$' -e '^module_path$' -e '^modules$' -e '^nameddirs$' -e '^options$' -e '^parameters$' -e '^patchars$' -e '^path$' -e '^pipestatus$' -e '^prompt$' -e '^psvar$' -e '^reset_color$' -e '^reswords$' -e '^saliases$' -e '^signals$' -e '^status$' -e '^termcap$' -e '^terminfo$' -e '^userdirs$' -e '^usergroups$' -e '^watch$' -e '^widgets$' -e '^zle_bracketed_paste$' -e '^zsh_eval_context$' -e '^zsh_scheduled_events$') || true


    local regvar=""
    local i=""
    # for i in ${regresult} ; do 
    for i in ${(f)regresult} ; do
        regvar+="$i"$'\n'
    done


    local newVars=""
    _safe_vars(){ 
        # remove all defined variable in bash in the actual session, with this it means if a variable is edited outside of bash and saved in reg then it will not be updated, so it is secure to use the new environment without worrying about overwriting a critical variable created by bash or other tool in cygwin in the future. so only the PATH and the newly added variables to reg which are not already defined inside the actual bash session will be added to the actual bash session.
    
        # print all defined variables in bash
        local bashvar=""
        # met1:
        # for i in $(set -o posix; set | grep '=') ; do 
            # bashvar+=$(echo "$i" | cut -d'=' -f1)$'\n'
        # done
        
        # met2
        # The bash builtin compgen was meant to be used in completion scripts. To this end, compgen -v lists all defined variables. The downside: it lists only the variable names, not the values.
        # and compgen -v prints more things than set 
        # bashvar=$(compgen -v)
        
        # there is no compgen in zsh
        # some blackmagic by Chazelas https://unix.stackexchange.com/questions/292903/list-names-of-aliases-functions-and-variables-in-zsh
        # we could have used only "set | cut -f1 -d = " or ${(k)parameters} or ${(k)parameters:#([[:alpha:]_][[:alnum:]_]#)} to get the same result,but those three examples will add those variables ! # $ * - 0 ? @ , and because we already filter any non standard variable above with grep -e '^[a-zA-Z_][a-zA-Z0-9_]*$' then those variables added by the three examples will not be overwrited anyway, but i will use the Chazelas method anyway because I may be wrong... 
        # Stéphane Chazelas: ${(kM)parameters:#[[:alpha:]_][[:alnum:]_]#} (with extendedglob) for only the parameters that are variables. –  Jun 22, 2017
        if [[ -o extendedglob ]]; then
            bashvar=$(print -rl -- ${(kM)parameters:#[[:alpha:]_][[:alnum:]_]#} | sort)
        else
            setopt extendedglob
            bashvar=$(print -rl -- ${(kM)parameters:#[[:alpha:]_][[:alnum:]_]#} | sort)
            setopt noextendedglob
        fi

                
        # compare reg variables to bash variables and print only variables that exist in reg and do not exist in bash, this of course means that if a variable is already defined in bash and it is updates in reg,then this variable will not be updated using this script, this is not good of course but it is safer, because i may override a critical bash variable otherwise
        # so with this method i will get all the new added variables but not the old variables which were recently updated
            # show lines that exist in string2 and do not exist in string1
            # grep's -x (--line-regexp) can be used to ensure the entire line is matched. So if A1 contains x and A2 contains xx, a match will not be found. 
            # You probably also need to use the option -F or --fixed-strings. Otherwise grep will be interpreting A1 as regular expressions. So if A1 contains the line .*, it will match everything. So the entire command would be: grep -vxF -f A1 A2 
            # i use grep -i because path is defined as Path in reg but defined as PATH in bash, so they will be considered different without -i
        newVars=$(grep -i -vxF -f <(echo "$bashvar") <(echo "$regvar"))
    }

    if [[ "${RefrEnv_StrictRefresh:-}" = "yes" ]] ; then
        _safe_vars
    else
        newVars="$regvar"
    fi
    
    # extract the values of the final key
    local newVarKeysAndValue0=""
    local newVarKeysAndValue==""
    # local ALLnewVarsKeysAndValues=""
    ALLnewVarsKeysAndValues=""
    
    # don t quote $newVars i already override IFS so no worry about space, if i quote it the multiline is considered one word
    local i=""
    # for i in $newVars ; do 
    for i in ${(f)newVars} ; do 
        if [[ "$i" != "" ]] ; then
            # if the variable have ' bad things may happen so lets escape it with '\''
            newVarKeysAndValue0=$(regtool get "${regPath}/${i}" | sed "s/'/'\\\\''/g" )
            newVarKeysAndValue="export ${i}='${newVarKeysAndValue0}'"
            ALLnewVarsKeysAndValues+="${newVarKeysAndValue}"$'\n'
        fi
    done

    # print vars if they do not contain variable which need to be expanded of the form %...% , because some apps may save the vars in reg unexpanded
    printf '%s' "$ALLnewVarsKeysAndValues" | grep -v -- '%.*%' >> "${RefrEnv_Temp_Dir}/newEnv.sh" || true
    
    # prepare vars list which need to be expanded
    # echo "" is needed to create some content in the text file otherwise the vbscript will gave error when the file is empty, (a new line here is considered a content)
    echo "" > "${RefrEnv_Temp_Dir}/vars_need_to_expand.txt"
    printf '%s' "$ALLnewVarsKeysAndValues" | grep -- '%.*%' >> "${RefrEnv_Temp_Dir}/vars_need_to_expand.txt" || true

    ExpandEnvironmentStrings "$(cygpath -w "${RefrEnv_Temp_Dir}/vars_need_to_expand.txt")" "$(cygpath -w "${RefrEnv_Temp_Dir}/vars_expanded.txt")"
    
    cat "${RefrEnv_Temp_Dir}/vars_expanded.txt" >> "${RefrEnv_Temp_Dir}/newEnv.sh"

    if [[ ${RefrEnv_debug:-} = yes ]] ; then
        echo "${regPath}" >> "${RefrEnv_Temp_Dir}/vars_need_to_expand_all.txt"
        echo "${regPath}" >> "${RefrEnv_Temp_Dir}/vars_expanded_all.txt"
        cat "${RefrEnv_Temp_Dir}/vars_need_to_expand.txt" >> "${RefrEnv_Temp_Dir}/vars_need_to_expand_all.txt"
        cat "${RefrEnv_Temp_Dir}/vars_expanded.txt" >> "${RefrEnv_Temp_Dir}/vars_expanded_all.txt"
        echo _______________________________ >> "${RefrEnv_Temp_Dir}/vars_need_to_expand_all.txt"
        echo _______________________________ >> "${RefrEnv_Temp_Dir}/vars_expanded_all.txt"
    fi
    
    rm "${RefrEnv_Temp_Dir}/vars_need_to_expand.txt" "${RefrEnv_Temp_Dir}/vars_expanded.txt"
    IFS="$IFSorg"
}


getNewPATHS(){ 
    local HKLM HKCU HKCUV
    HKLM=$(regtool get '/HKLM/System/CurrentControlSet/Control/Session Manager/Environment/path')
    # '/HKCU/Environment/path' and '/HKCU/Volatile Environment/path' are not always defined so let s hide the stderror 
    HKCU=$(regtool get '/HKCU/Environment/path' 2>/dev/null) || true
    HKCUV=$(regtool get '/HKCU/Volatile Environment/path' 2>/dev/null) || true

    # TODO: check here if we should do ${HKLM};${HKCU} or  ${HKCU};${HKLM} based on what the supported shells do, i think i should do ${HKCU};${HKLM}
    local allPATHs="${HKLM};${HKCU};${HKCUV}"
    
    # after installing chocolatey it adds itself to the path like that: (D:\ProgramData\chocolatey\bin;) , the last ; should not have been added by chocolatey, this is an error by chocolatey , and it cause allPATHs to have double ;; , and this will make cygpath print (cygpath: can't convert empty path) . to solve it lets replace the double ;; with one ; this is safe. this solve https://github.com/badrelmers/RefrEnv/issues/1
    # printf '%s' "$allPATHs" | sed -e 's/;;/;/g' -e 's/;$//g'  > "${RefrEnv_Temp_Dir}/path_need_to_expand.txt"
    # it s better to use ;;* so we can catch multiple ; like ;;; or ;;;;
    printf '%s' "$allPATHs" | sed -e 's/;;*/;/g' -e 's/;$//g'  > "${RefrEnv_Temp_Dir}/path_need_to_expand.txt"
    ExpandEnvironmentStrings "$(cygpath -w "${RefrEnv_Temp_Dir}/path_need_to_expand.txt")" "$(cygpath -w "${RefrEnv_Temp_Dir}/path_expanded.txt")"
    local AllExpandedPaths
    AllExpandedPaths=$(cat "${RefrEnv_Temp_Dir}/path_expanded.txt")
     
    
    local IFSorg="$IFS"
    local i convertedPATHs DefaultPath OSPATH_fromReg convertedItem convertedPATHs_FromWin convertedPATHs_FromBash

    IFS=';'
    # for i in ${AllExpandedPaths} ; do 
    # for i in ${(f)AllExpandedPaths} ; do 
    for i in ${(s/;/)AllExpandedPaths} ; do 
        # convert the windows path to the equivalent cygwin path format: cygdrive...
        convertedItem=$(cygpath "$i")
        convertedPATHs_FromWin+="${convertedItem}"$'\n'
        OSPATH_fromReg+="${convertedItem}:"
    done
    # remove the last ':'
    OSPATH_fromReg=$(printf '%s\n' "$OSPATH_fromReg" | sed 's/:$//g')
    
    if [[ ${RefrEnv_ResetPath:-} != yes ]] ; then
        # append the new paths to the old path; its better than overwriting the old path; otherwise i will delete any newly added path by the script who called this script
        IFS=':'
        # for i in ${PATH} ; do 
        # for i in ${(f)PATH} ; do 
        for i in ${(s/:/)PATH} ; do 
            convertedPATHs_FromBash+="$i"$'\n'
        done
    fi
    
    if [[ ${RefrEnv_ResetPath:-} == yes ]] ; then
        # reset the path : read the text of the function how_to_open_a_clean_bash_session() for more details
        # lets open a new bash session then capture the new path then add that path to our path, otherwise the bash default path will also be reseted so no command will work after that
        # check if we are in a login shell
        # if shopt -q login_shell ; then
        if [[ -o login ]] ; then
            # we are in a login shell
            # env -i clears HOME, so even if you run bash -l on the inside, it won't read your .bash_profile etc .so to solve it we use HOME="$HOME" https://unix.stackexchange.com/questions/48994/how-to-run-a-program-in-a-clean-environment-in-bash/451389#451389
            # env -i adds a dot (.) to the path!, this is bad so lets remove that dot with sed
            # DefaultPath=$(env -i HOME="$HOME" /bin/bash -lc 'echo $PATH' | sed -e 's/:\.:/:/' -e 's/:\.$//')
            # the above some times work badly see: https://github.com/badrelmers/RefrEnv/issues/1
            
            # solution:
            # sourcing ${RefrEnv_Temp_Dir}/newEnv.sh inside bash running by env -i is super important because if some variable in .bash_profile...etc need a variable that is setup in the OS registry then it will fail because env -i do not setup those variables like a fresh bash do when we run it manually (I mean env -i do not inherit explorer env) , so we source newEnv.sh to setup those variables to have the same environment as a fresh bash 
            # but remember that maybe .bash_profile...etc need some other variable that env -i strips, so be prepared to add more variables here like i did with $HOME $USER $LC_ALL ...etc
            # DefaultPath=$(env -i RefrEnvSetupEnv="${RefrEnv_Temp_Dir}/newEnv.sh" HOME="$HOME" LANGUAGE="${LANGUAGE:-}" LANG="${LANG:-}" LC_ALL="${LC_ALL:-}" USER="$USER" TERM="${TERM:-}" PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:$OSPATH_fromReg" "$BASH" -l -c 'source "${RefrEnvSetupEnv}" >/dev/null 2>/dev/null; printf "%s\n" "$PATH"' | sed -e 's/:\.:/:/' -e 's/:\.$//')
            
            # a better solution i found finally is to use env -u PATH instead of env -i... this is a life saver!
                # -u, --unset=NAME   remove variable from the environment
            # it is good to unset ORIGINAL_PATH too otherwise ...etc\profile of msys2/git bash will use it to setup the new PATH and if it contain an old dir we do not want then it will be inherited in the new PATH
            # so with this solution we can pass all our actual environment to the new bash session and exclude the  PATH
            DefaultPath=$(env -u PATH -u ORIGINAL_PATH PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:$OSPATH_fromReg" zsh -l -c 'printf "%s\n" "$PATH"' | sed -e 's/:\.:/:/' -e 's/:\.$//')
        else
            DefaultPath=$(env -u PATH -u ORIGINAL_PATH PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:$OSPATH_fromReg" zsh    -c 'printf "%s\n" "$PATH"' | sed -e 's/:\.:/:/' -e 's/:\.$//')
        fi

        # if Chazelas say something about the shell then take it with the eyes closed :) https://unix.stackexchange.com/questions/614299/how-to-split-a-string-by-character-in-bash-zsh
        IFS=':'
        # for i in ${DefaultPath} ; do 
        # for i in ${(f)DefaultPath} ; do 
        for i in ${(s/:/)DefaultPath} ; do 
            convertedPATHs_FromBash+="$i"$'\n'
        done
    fi

    # the order here is very important , if we put $convertedPATHs_FromWin before $convertedPATHs_FromBash then for example we will be using 'sort' of windows not of bash
    convertedPATHs="$convertedPATHs_FromBash$convertedPATHs_FromWin"

    # remove the last slash / so i catch duplicates which differ in the last slash only like: abc:abc/
    convertedPATHs=$(printf '%s' "$convertedPATHs" | sed 's/\/$//g')

    # remove duplicates without sorting
    # case insensitive
    local uniqpath
    uniqpath=$(printf '%s' "$convertedPATHs" | nl | sort --ignore-case -u -k2 | sort -n | cut -f2-)
    
    # convert it to cygwin PATH format ...:...:...etc
    local finalpath
    finalpath=$(printf '%s' "$uniqpath" | tr '\n' ':')
    # if the variable have single quote ' , bad things may happen so lets escape it with '\''
    finalpath=$(printf '%s' "$finalpath" | sed "s/'/'\\\\''/g")

    finalpath="export PATH='${finalpath}'"
    printf '%s' "$finalpath" >> "${RefrEnv_Temp_Dir}/newEnv.sh"

    
    IFS="$IFSorg"
}


ExpandEnvironmentStrings(){ 
    printf '%s' '
strFilename=WScript.Arguments.Item(0)
outFilename=WScript.Arguments.Item(1)

Set fso=CreateObject("Scripting.FileSystemObject")
REM Read file
set objFile=fso.OpenTextFile(strFilename,1)
oldContent=objFile.ReadAll

REM expand variables
set WshShell = WScript.CreateObject("WScript.Shell")
newContent = WshShell.ExpandEnvironmentStrings(oldContent)

REM Write file:  ForAppending = 8 ForReading = 1 ForWriting = 2 , True=create file if not exist
set objFile=fso.OpenTextFile(outFilename,2,True)
objFile.Write newContent
objFile.Close
    ' > "${RefrEnv_Temp_Dir}/ExpandEnvironmentStrings.vbs"

    cscript //nologo "$(cygpath -w "${RefrEnv_Temp_Dir}/ExpandEnvironmentStrings.vbs")" "$1" "$2"
}

refrenv_main

# end subshell
)


#########################################################################
#########################################################################
#########################################################################

if [[ ${RefrEnv_help:-} != yes ]] ; then
    # finally set the new variables
    source "${RefrEnv_Temp_Dir}/newEnv.sh"


    # cleanup
    if [[ ${RefrEnv_debug:-} = yes ]] ; then
        # explorer exit code is 1 always!!!
        explorer "$(cygpath -w "${RefrEnv_Temp_Dir}")" || true
    else
        rm -rf "${RefrEnv_Temp_Dir}"
    fi
fi

unset RefrEnv_Temp_Dir



### end ######################################################################





### some details######################################################################

how_to_open_a_clean_bash_session(){
    # test to show how to run a new bash session with a clean environment, well in fact i want a new bash session without some env var like PATH, but i want to keep important var needed by other apps like $HOME $USER $LC_ALL


    PATH="00000000000000000000000000000:$PATH"

    # _________________cygwin 
    bash -c 'echo $PATH'      # baaaaaaaaad this do not reset the path
    bash -lc 'echo $PATH'     # baaaaaaaaad this do not reset the path

    # _________________git bash
    bash -c 'echo $PATH'      # baaaaaaaaad this do not reset the path
    bash -lc 'echo $PATH'     # goooooooooood this reset the path because it reads "D:\Program Files\Git\etc\profile" which reset the path


    # so i need to use env -i to solve it for cygwin

    # _________________git bash
    # - baaaaaaaaad : 2 errors
    env -i HOME=$HOME /bin/bash -lc 'echo $PATH'
    # return 
        # which: no bash in ((null))
        # /d/Users/LLED2/.bash_profile: line 7: oh-my-posh: command not found
        # /d/Users/LLED2/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:.:/usr/bin/vendor_perl:/usr/bin/core_perl

    # - this is usefull only if the parent script is not a login shell
    env -i HOME=$HOME /bin/bash -c 'echo $PATH'
        # return /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:.

    # - baaaaaaaaad this do not reset the path : 0000000...
    env HOME=$HOME /bin/bash -c 'echo $PATH'
        # return 00000000000000000000000000000:/d/Users/LLED2/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/bin:/mingw64/bin:/usr/bin:/d/Users/LLED2/bin:/d/Windows/system32:/d/Windows:/d/Windows/System32/Wbem:/d/Windows/System32/WindowsPowerShell/v1.0:......:/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/bin:/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/themes:/usr/bin/vendor_perl:/usr/bin/core_perl

    # - goooooooooood this reset the path
    env HOME=$HOME /bin/bash -lc 'echo $PATH'
        # return /d/Users/LLED2/bin:/mingw64/bin:/usr/local/bin:/usr/bin:/bin:/mingw64/bin:/usr/bin:/d/Users/LLED2/bin:/d/Windows/system32:/d/Windows:/d/Windows/System32/Wbem:/d/Windows/System32/WindowsPowerShell/v1.0:......:/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/bin:/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/themes:/usr/bin/vendor_perl:/usr/bin/core_perl

    # _________________cygwin
    # - baaaaaaaaad : 1 error
    env -i HOME=$HOME /bin/bash -lc 'echo $PATH'
    # return
        # /home/LLED2/.bash_profile: line 63: oh-my-posh: command not found
        # /usr/local/bin:/usr/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:.

    # - this is usefull only if the parent script is not a login shell
    env -i HOME=$HOME /bin/bash -c 'echo $PATH'
        # return /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:.

    # - baaaaaaaaad this do not reset the path
    env HOME=$HOME /bin/bash -c 'echo $PATH'
        # return 00000000000000000000000000000:/cygdrive/F/_bin/_bin/git/_PortableGit/_last/cmd:/usr/local/bin:/usr/bin:/cygdrive/d/Windows/system32:/cygdrive/d/Windows:/cygdrive/d/Windows/System32/Wbem:/cygdrive/d/Windows/System32/WindowsPowerShell/v1.0:......:/cygdrive/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/bin:/cygdrive/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/themes:/usr/lib/lapack:/home/LLED2/.local/bin:/home/LLED2/_bin

    # - baaaaaaaaad this do not reset the path
    env HOME=$HOME /bin/bash -lc 'echo $PATH'
        # return /cygdrive/F/_bin/_bin/git/_PortableGit/_last/cmd:00000000000000000000000000000:/cygdrive/F/_bin/_bin/git/_PortableGit/_last/cmd:/usr/local/bin:/usr/bin:/cygdrive/d/Windows/system32:/cygdrive/d/Windows:/cygdrive/d/Windows/System32/Wbem:/cygdrive/d/Windows/System32/WindowsPowerShell/v1.0:......:/cygdrive/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/bin:/cygdrive/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/themes:/usr/lib/lapack:/home/LLED2/.local/bin:/home/LLED2/_bin:/home/LLED2/.local/bin:/home/LLED2/_bin

    ####################
    # solution:
    ####################
    # if we r in non login bash then we use:
    env -i HOME=$HOME /bin/bash -c 'echo $PATH'


    # if we r in login bash then we use one of this:
    # _________________solution1: the best
    # we can use this: add default bash path manually ,it solves the error 'which: no bash in ((null))' which happen in git bash and msys2:
    # this happen because "D:\Program Files\Git\etc\profile" use SHELL=`which bash`, and because the PATH is not exported then 'which' cannot read the PATH (if I use export inside ...etc\profile then 'which' work fine: the ((null)) simply means that the PATH is not setup). but why PATH is not exported automatically? I found a nice explination here https://unix.stackexchange.com/questions/50282/usr-bin-which-returns-cryptic-error-which-no-ls-in-null
        # I had the same problem (using bash). It seems, a bash "feature" turns into a miss-feature: Bash creates a shell variable (not environment variable!) PATH which it then uses for lookups.
        # So, the situation is: There exists a shell variable called PATH. But it's not an environment variable. This means, it's not exported to newly created child processes. One thing, we should learn from this, is that using echo $PATH is no way to figure out whether the environment variable PATH is set. Same prolem with set | grep "^PATH=" However, one way to do so is by using the external command env: env | grep "^PATH="
        # ...
        # Depending on what you're trying to achieve, you can ask the shell to act like a login shell, for bash it's -l. With that, /etc/profile and other files are sources which set up PATH properly by default:
        # env -i bash -l
        # The alternative, is to export PATH, see above.

    # his solution to use bash -l will not work in our case here because the problem happen ...etc\profile before that ...etc\profile even export the PATH
        # so to solve this we need to pass the PATH to env -i , because it seems that env will export the PATH for us, see this test:
        env -i HOME=$HOME "$BASH" -c 'env | grep "^PATH="'
            # return nothing
        env -i HOME=$HOME PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin "$BASH" -c 'echo $PATH'
            # return /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin

    # so the solution is to use:
        env -i HOME=$HOME PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin "$BASH" -lc 'echo $PATH'

    # we solved the first error but we still have this error 'oh-my-posh: command not found', it happens in cygwin and git bash (because the path do not contain the OS path inhereited by the explorer, the PATH contain only cygwin/msys2 path):
        # /d/Users/LLED2/.bash_profile: line 7: oh-my-posh: command not found

    # to solve it we can do:
    # met1: hide the error because it s not important to run correctly the bash_profile because we only want the path here, but if the bash_profile setup any path entry based on a the existence of a command then this will be a bad solution or even dangerous   
        env -i HOME=$HOME PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin" bash -lc 'echo $PATH' 2>/dev/null || true

    # met2: append the OS path we get from the reg : this is the safest method
        env -i HOME=$HOME PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:$OSPATH_fromReg" "$BASH" -lc 'echo $PATH'

        
    # met3: a better solution i found finally is to use env -u PATH instead of env -i... this is a life saver!
        # -u, --unset=NAME   remove variable from the environment
    # it is good to unset ORIGINAL_PATH too otherwise ...etc\profile of msys2/git bash will use it to setup the new PATH and if it contain an old dir we do not want then it will be inherited in the new PATH
    # so with this solution we can pass all our actual environment to the new bash session and exclude the  PATH
        OSPATH_fromReg=/d/Users/LLED2/AppData/Local/Programs/oh-my-posh/bin
        env -u PATH -u ORIGINAL_PATH PATH="/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:$OSPATH_fromReg" "$BASH" -l -c 'printf "%s\n" "$PATH"'


    # _________________solution2: I don t like this solution
    # one solution that works too is to not use the -l with bash, but if the parent script who called refrenv used -l, then the path will not contain entries that are created when -l is used normally
        env -i HOME=$HOME /bin/bash -c 'echo $PATH'

    # _________________solution3: hackish
    # this work to reset the env but i cannot capture the output
    explorer "$(cygpath -w $(env bash))"

    # but i can create a bat file then call "explorer file.bat" and run bash from it and capture the path , this will be best , but calling explorer is a litle bit hackish

    # _________________solution4: TODO
    # case "$(uname -s)" in
       # CYGWIN*)  echo 'CYGWIN' ;;
       # MINGW*)   echo 'MINGW' ;;
       # MSYS*|)   echo 'MSYS' ;;
       # *)        echo 'Other bash OS' ;;
    # esac
    # or 
    # case "$OSTYPE" in
      # msys*)    echo "MSYS / MinGW / Git Bash" ;;
      # cygwin*)  echo "Cygwin" ;;
      # *)        echo "unknown: $OSTYPE" ;;
    # esac


    # __________________________more details
    # https://unix.stackexchange.com/questions/48994/how-to-run-a-program-in-a-clean-environment-in-bash
    # env -i clears HOME, so even if you run bash -l on the inside, it won't read your .bash_profile etc. If what you're looking for is a shell that acts as if you had just done a fresh login, you'd want this instead:
    # env -i HOME="$HOME" bash -l -c 'your_command'

    # ________
    # env -i somecommand runs a command in an empty environment, as ams has already mentioned.
    # A lot of programs rely on some important environment variables, so you may want to retain them:
    # env -i HOME="$HOME" LC_CTYPE="${LC_ALL:-${LC_CTYPE:-$LANG}}" PATH="$PATH" USER="$USER" somecommand

    # ________
    # You can get a fresh environment for the bash shell via env -i USER=user HOME=/home/user PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin bash -l. You really only need to set the USER, HOME, and PATH environment variables; plus LANGUAGE, LANG, and LC_ALL or other LC_ ones if you want some locale other than the default POSIX/C one; TERM (and -i option to bash) if interactive or use a terminal, and DISPLAY if using X11. But honestly, a PAM module is a much easier option. It's not nearly as hard to write the module as you might think. –  https://stackoverflow.com/questions/18094242/how-can-i-call-bash-from-c-with-a-clean-environment

    # ________
    # more reads:
    # https://unix.stackexchange.com/questions/341999/can-bash-script-reset-sanitize-whole-environment-and-how
    # https://unix.stackexchange.com/questions/446571/isolated-subshells-in-bash

    
}