NSIS安装程序运行时提示环境变量为空的问题求助

尝试用NSIS制作安装程序时，运行时读取环境变量多次失败，以下是尝试的方法及结果：

1. 使用ReadEnvStr方法 #

创建basic.nsi脚本：

!include "LogicLib.nsh"
Outfile "TestInstaller.exe"
Name "Test Installer"
InstallDir $DESKTOP\MyApp

Section "Install"
    ReadEnvStr $R0 "MY_VAR"
    ${If} $R0 == ""
        MessageBox MB_OK "MY_VAR is not set or is empty"
    ${Else}
        MessageBox MB_OK "MY_VAR value: $R0"
    ${EndIf}
SectionEnd

在PowerShell中执行：

> makensis basic.nsi
> set MY_VAR=1
> ./TestInstaller.exe

运行后提示MY_VAR is not set or is empty。

2. 使用系统调用GetEnvironmentVariableA #

编写NSIS脚本：

Outfile "TestInstaller.exe"
Name "Test Installer"
InstallDir $DESKTOP\MyApp

Section "Install"
    System::Call 'kernel32::GetEnvironmentVariableA(t "MY_VAR", t .R0, i ${NSIS_MAX_STRLEN}) i .r1'

    IntCmp $R1 0 env_not_found env_found

    env_not_found:
        MessageBox MB_OK "MK_UPDATE_INSTALLER is not set or is empty"
        Goto end

    env_found:
        MessageBox MB_OK "MK_UPDATE_INSTALLER value: $R0"

    end:
SectionEnd

运行后仍提示环境变量未设置或为空。

3. 遍历所有环境变量 #

编写遍历脚本：

Outfile "PrintEnvVarsInstaller.exe"
Name "Print Env Vars Installer"
InstallDir $DESKTOP\MyApp

Section "Install"
    ; Get a pointer to the environment block
    System::Call 'kernel32::GetEnvironmentStringsA() p .r0'

    ; Initialize a pointer variable to iterate over the environment block
    StrCpy $R1 $R0

    loop:
    ; Get the current string pointed to by $R1
    System::Call '*$R1(&t0 .R2)'

    ; Check if we reached the end of the environment block (null string)
    StrCmp $R2 "" done

    ; Display the current environment variable
    MessageBox MB_OK "$R2"

    ; Move the pointer to the next string (environment variable)
    System::Call 'kernel32::lstrlenA(t $R2) i .r3'
    IntOp $R1 $R1 + $R3
    IntOp $R1 $R1 + 1

    ; Repeat the loop
    Goto loop

    done:
    ; Free the environment strings block
    System::Call 'kernel32::FreeEnvironmentStringsA(p $R0) i .r1'

    MessageBox MB_OK "done"

SectionEnd

运行后直接弹出done，未检测到任何环境变量。

注意：使用Python的os.getenv和PowerShell的Write-Host "MY_VAR is set to: $env:MY_VAR"均可正常读取该环境变量。

问题原因与解决方法 #

核心原因 #

NSIS默认以管理员权限运行安装程序时，会触发Windows的UAC虚拟化机制，导致程序运行在不同的环境上下文，无法继承当前普通用户PowerShell会话中的环境变量。

解决方法 #

方法1：禁用UAC虚拟化（推荐）

在NSIS脚本中添加UAC相关配置，明确指定不使用虚拟化，并确保安装程序以当前用户权限运行（如果不需要管理员权限）：

!include "LogicLib.nsh"
!include "UAC.nsh"

Outfile "TestInstaller.exe"
Name "Test Installer"
InstallDir $DESKTOP\MyApp

; 禁用UAC虚拟化，确保环境变量继承
RequestExecutionLevel user ; 以当前用户权限运行，不提升
SetShellVarContext all

Section "Install"
    ReadEnvStr $R0 "MY_VAR"
    ${If} $R0 == ""
        MessageBox MB_OK "MY_VAR is not set or is empty"
    ${Else}
        MessageBox MB_OK "MY_VAR value: $R0"
    ${EndIf}
SectionEnd

方法2：如果必须以管理员权限运行

若安装程序需要管理员权限，可通过以下方式传递环境变量：

1. 在PowerShell中设置用户级环境变量并刷新：

[Environment]::SetEnvironmentVariable("MY_VAR", "1", "User")
# 重启PowerShell后运行安装程序，管理员进程可读取用户级环境变量

2. 或者在启动安装程序时直接传递参数：
   修改NSIS脚本接收命令行参数：

!include "LogicLib.nsh"
Outfile "TestInstaller.exe"
Name "Test Installer"
InstallDir $DESKTOP\MyApp

Section "Install"
    ; 读取命令行参数中的MY_VAR值
    ${GetParameters} $R0
    StrCpy $R1 ""
    ${GetOptions} $R0 "/MY_VAR=" $R1
    ${If} $R1 == ""
        MessageBox MB_OK "MY_VAR is not provided"
    ${Else}
        MessageBox MB_OK "MY_VAR value: $R1"
    ${EndIf}
SectionEnd

然后在PowerShell中运行：

> ./TestInstaller.exe /MY_VAR=1

方法3：修复遍历环境变量的脚本

原遍历脚本中System::Call '*$R1(&t0 .R2)'的写法有误，正确的读取内存中字符串的方式如下：

Outfile "PrintEnvVarsInstaller.exe"
Name "Print Env Vars Installer"
InstallDir $DESKTOP\MyApp

Section "Install"
    System::Call 'kernel32::GetEnvironmentStringsA() p .r0'
    StrCpy $R1 $R0

    loop:
    ; 正确读取内存中的C字符串
    System::Call 'kernel32::lstrcpynA(t .R2, p $R1, i ${NSIS_MAX_STRLEN})'
    StrCmp $R2 "" done

    MessageBox MB_OK "$R2"

    ; 计算下一个字符串的指针
    System::Call 'kernel32::lstrlenA(p $R1) i .r3'
    IntOp $R1 $R1 + $R3
    IntOp $R1 $R1 + 1

    Goto loop

    done:
    System::Call 'kernel32::FreeEnvironmentStringsA(p $R0) i .r1'
    MessageBox MB_OK "done"
SectionEnd

内容的提问来源于stack exchange，提问作者user236529