Setting Environment Variables

Author: KiCHiK (talk, contrib)

Setting Environmental Variables Temporarily

If you want to set an environment variable only for the installer process and its sub-processes use:

System::Call 'Kernel32::SetEnvironmentVariableA(t, t) i("name", "value").r0'
StrCmp $0 0 error
  ExecWait ProgThatReadsEnv.exe
  Goto done
error:
  MessageBox MB_OK "Can't set environment variable"
done:

Author: turnec2 (talk, contrib)

Setting Environmental Variables Permanently

Exisiting Variables

The WriteEnvStr and un.DeleteEnvStr functions in this page have been obsoleted by EnvVarUpdate. The un.DeleteEnvStr function can corrupt the contents of the PATH variable if the path being removed happens to be a subset of another path. For example, if PATH contains "C:\Windows\system32\wbem" and you remove "C:\Windows\system32" the result is "\wbem". WriteEnvStr does not prevent the duplication of entries if the user runs the installer multiple times (and the installer code does not otherwise check for duplicates). However, these routines are retained for Windows 9x and ME in the next section since EnvVarUpdate does not support the update of variables in the autoexec.bat file.

See Environmental_Variables:_append,_prepend,_and_remove_entries for more information.

Your own variable

If you're setting / deleting your own environment variable MYVAR, rather than adjusting an existing one such as the PATH environment variable:

   ; include for some of the windows messages defines
   !include "winmessages.nsh"
   ; HKLM (all users) vs HKCU (current user) defines
   !define env_hklm 'HKLM "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"'
   !define env_hkcu 'HKCU "Environment"'
   ; set variable
   WriteRegExpandStr ${env_hklm} MYVAR MYVAL
   ; make sure windows knows about the change
   SendMessage ${HWND_BROADCAST} ${WM_WININICHANGE} 0 "STR:Environment" /TIMEOUT=5000

And for your uninstaller

   ; delete variable
   DeleteRegValue ${env_hklm} MYVAR
   ; make sure windows knows about the change
   SendMessage ${HWND_BROADCAST} ${WM_WININICHANGE} 0 "STR:Environment" /TIMEOUT=5000

Function Code

[EnvVarUpdate function code]

Author: KiCHiK (talk, contrib)

Functions for Windows 95, 98, and ME

If you want to set an environment variable that will stick for every other process and after reboots too you should use the functions below. To use them either save them as a .NSH file and include them in your script, or just copy paste them in your script. If you choose to save them as a .NSH file use:

!include WriteEnvStr.nsh # or the name you chose
# ...
Section "Add Env Var"
  Push MyEnvVar
  Push MyEnvVarValue
  Call WriteEnvStr
SectionEnd
# ...
Section uninstall
  # remove the variable
  Push MyEnvVar
  Call un.DeleteEnvStr
SectionEnd

If you want the environment variable to be available to all of the users using the computer define ALL_USERS before you include WriteEnvStr.nsh (or before the part of the script holding these functions if you didn't save it as a .NSH file). For example:

!define ALL_USERS
!include WriteEnvStr.nsh # or the name you chose

Function Code

Note: under Windows 9x a reboot is required for changes to take effect. The reboot flag will be set by these functions if a reboot is required. Warning: this script will only work on NSIS 2.0b2 and above!

!ifndef _WriteEnvStr_nsh
!define _WriteEnvStr_nsh
 
!include WinMessages.nsh
 
!ifndef WriteEnvStr_RegKey
  !ifdef ALL_USERS
    !define WriteEnvStr_RegKey \
       'HKLM "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"'
  !else
    !define WriteEnvStr_RegKey 'HKCU "Environment"'
  !endif
!endif
 
#
# WriteEnvStr - Writes an environment variable
# Note: Win9x systems requires reboot
#
# Example:
#  Push "HOMEDIR"           # name
#  Push "C:\New Home Dir\"  # value
#  Call WriteEnvStr
#
Function WriteEnvStr
  Exch $1 ; $1 has environment variable value
  Exch
  Exch $0 ; $0 has environment variable name
  Push $2
 
  Call IsNT
  Pop $2
  StrCmp $2 1 WriteEnvStr_NT
    ; Not on NT
    StrCpy $2 $WINDIR 2 ; Copy drive of windows (c:)
    FileOpen $2 "$2\autoexec.bat" a
    FileSeek $2 0 END
    FileWrite $2 "$\r$\nSET $0=$1$\r$\n"
    FileClose $2
    SetRebootFlag true
    Goto WriteEnvStr_done
 
  WriteEnvStr_NT:
      WriteRegExpandStr ${WriteEnvStr_RegKey} $0 $1
      SendMessage ${HWND_BROADCAST} ${WM_WININICHANGE} \
        0 "STR:Environment" /TIMEOUT=5000
 
  WriteEnvStr_done:
    Pop $2
    Pop $0
    Pop $1
FunctionEnd
 
#
# un.DeleteEnvStr - Removes an environment variable
# Note: Win9x systems requires reboot
#
# Example:
#  Push "HOMEDIR"           # name
#  Call un.DeleteEnvStr
#
Function un.DeleteEnvStr
  Exch $0 ; $0 now has the name of the variable
  Push $1
  Push $2
  Push $3
  Push $4
  Push $5
 
  Call un.IsNT
  Pop $1
  StrCmp $1 1 DeleteEnvStr_NT
    ; Not on NT
    StrCpy $1 $WINDIR 2
    FileOpen $1 "$1\autoexec.bat" r
    GetTempFileName $4
    FileOpen $2 $4 w
    StrCpy $0 "SET $0="
    SetRebootFlag true
 
    DeleteEnvStr_dosLoop:
      FileRead $1 $3
      StrLen $5 $0
      StrCpy $5 $3 $5
      StrCmp $5 $0 DeleteEnvStr_dosLoop
      StrCmp $5 "" DeleteEnvStr_dosLoopEnd
      FileWrite $2 $3
      Goto DeleteEnvStr_dosLoop
 
    DeleteEnvStr_dosLoopEnd:
      FileClose $2
      FileClose $1
      StrCpy $1 $WINDIR 2
      Delete "$1\autoexec.bat"
      CopyFiles /SILENT $4 "$1\autoexec.bat"
      Delete $4
      Goto DeleteEnvStr_done
 
  DeleteEnvStr_NT:
    DeleteRegValue ${WriteEnvStr_RegKey} $0
    SendMessage ${HWND_BROADCAST} ${WM_WININICHANGE} \
      0 "STR:Environment" /TIMEOUT=5000
 
  DeleteEnvStr_done:
    Pop $5
    Pop $4
    Pop $3
    Pop $2
    Pop $1
    Pop $0
FunctionEnd
 
!ifndef IsNT_KiCHiK
!define IsNT_KiCHiK
 
#
# [un.]IsNT - Pushes 1 if running on NT, 0 if not
#
# Example:
#   Call IsNT
#   Pop $0
#   StrCmp $0 1 +3
#     MessageBox MB_OK "Not running on NT!"
#     Goto +2
#     MessageBox MB_OK "Running on NT!"
#
!macro IsNT UN
Function ${UN}IsNT
  Push $0
  ReadRegStr $0 HKLM \
    "SOFTWARE\Microsoft\Windows NT\CurrentVersion" CurrentVersion
  StrCmp $0 "" 0 IsNT_yes
  ; we are not NT.
  Pop $0
  Push 0
  Return
 
  IsNT_yes:
    ; NT!!!
    Pop $0
    Push 1
FunctionEnd
!macroend
!insertmacro IsNT ""
!insertmacro IsNT "un."
 
!endif ; IsNT_KiCHiK
 
!endif ; _WriteEnvStr_nsh