Shutting down windows using golang code

Question

I am making a program that automates some tedious tasks for me, after the program is done I want to shutdown windows. I know this can be done in for example C#

How can I shutdown window using golang?

Answer 1

There is no "Shutdown OS" function in the syscall package, because there is no common interface provided for that by all operating systems.

^{Note: there is a syscall.Shutdown() function, but that is to shutdown a socket, and not to shutdown the operating system.}

The easiest would be to just execute the shutdown command using the os/exec package, e.g.

if err := exec.Command("cmd", "/C", "shutdown", "/s").Run(); err != nil {
    fmt.Println("Failed to initiate shutdown:", err)
}

The above command initiates a shutdown sequence which usually takes 1 minute to really shut down the system (and there's room to abort it with shutdown /a). You may provide different arguments to the shutdown command to not wait 1 minute but proceed immediately: shutdown /t 0 /s (execute shutdown /? to get a list of all options).

There is also a Windows API call to shutdown the system: ExitWindowsEx(). It has 2 parameters, first is the flags to define the shutdown type (0x08 means Shuts down the system and turns off the power.), second is to provide a reason for the shutdown. To call this from Go, you can do that like this:

user32 := syscall.MustLoadDLL("user32")
defer user32.Release()

exitwin := user32.MustFindProc("ExitWindowsEx")

r1, _, err := exitwin.Call(0x08, 0)
if r1 != 1 {
    fmt.Println("Failed to initiate shutdown:", err)
}

But know that you need SE_SHUTDOWN_NAME privilege to call ExitWindowsEx(), else you get an error message like:

Failed to initiate shutdown: A required privilege is not held by the client.

See this example how to acquire the required privilege.

Answer 2

Thanks for the post, very helpful. here is a complete function that performs a reboot. It follows exactly the Microsoft example as noted before. should help saving time in figuring out the structs:

import (
    "fmt"
    "syscall"
    "unsafe"
)

// error is nil on success
func reboot() error {

    user32 := syscall.MustLoadDLL("user32")
    defer user32.Release()

    kernel32 := syscall.MustLoadDLL("kernel32")
    defer user32.Release()

    advapi32 := syscall.MustLoadDLL("advapi32")
    defer advapi32.Release()

    ExitWindowsEx := user32.MustFindProc("ExitWindowsEx")
    GetCurrentProcess := kernel32.MustFindProc("GetCurrentProcess")
    GetLastError := kernel32.MustFindProc("GetLastError")
    OpenProdcessToken := advapi32.MustFindProc("OpenProcessToken")
    LookupPrivilegeValue := advapi32.MustFindProc("LookupPrivilegeValueW")
    AdjustTokenPrivileges := advapi32.MustFindProc("AdjustTokenPrivileges")

    currentProcess, _, _ := GetCurrentProcess.Call()

    const tokenAdjustPrivileges = 0x0020
    const tokenQuery = 0x0008
    var hToken uintptr

    result, _, err := OpenProdcessToken.Call(currentProcess, tokenAdjustPrivileges|tokenQuery, uintptr(unsafe.Pointer(&hToken)))
    if result != 1 {
        fmt.Println("OpenProcessToken(): ", result, " err: ", err)
        return err
    }
    //fmt.Println("hToken: ", hToken)

    const SeShutdownName = "SeShutdownPrivilege"

    type Luid struct {
        lowPart  uint32 // DWORD
        highPart int32  // long
    }
    type LuidAndAttributes struct {
        luid       Luid   // LUID
        attributes uint32 // DWORD
    }

    type TokenPrivileges struct {
        privilegeCount uint32 // DWORD
        privileges     [1]LuidAndAttributes
    }

    var tkp TokenPrivileges

    result, _, err = LookupPrivilegeValue.Call(uintptr(0), uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(SeShutdownName))), uintptr(unsafe.Pointer(&(tkp.privileges[0].luid))))
    if result != 1 {
        fmt.Println("LookupPrivilegeValue(): ", result, " err: ", err)
        return err
    }
    //fmt.Println("LookupPrivilegeValue luid: ", tkp.privileges[0].luid)

    const SePrivilegeEnabled uint32 = 0x00000002

    tkp.privilegeCount = 1
    tkp.privileges[0].attributes = SePrivilegeEnabled

    result, _, err = AdjustTokenPrivileges.Call(hToken, 0, uintptr(unsafe.Pointer(&tkp)), 0, uintptr(0), 0)
    if result != 1 {
        fmt.Println("AdjustTokenPrivileges() ", result, " err: ", err)
        return err
    }

    result, _, _ = GetLastError.Call()
    if result != 0 {
        fmt.Println("GetLastError() ", result)
        return err
    }

    const ewxForceIfHung = 0x00000010
    const ewxReboot = 0x00000002
    const shutdownReasonMajorSoftware = 0x00030000

    result, _, err = ExitWindowsEx.Call(ewxReboot|ewxForceIfHung, shutdownReasonMajorSoftware)
    if result != 1 {
        fmt.Println("Failed to initiate reboot:", err)
        return err
    }

    return nil
}