How to Print to the Command Window from a Go GUI Application Compiled with `-ldflags -H=windowsgui`?

How to Print Output to Command Window for GUI Applications Compiled with -ldflags -H=windowsgui

Compiling a Go application with -ldflags -H=windowsgui for use as a graphical user interface (GUI) can present challenges in printing output to the command window. This is because GUI processes on Windows are typically not associated with a console.

Problem

When an application is compiled with the -H=windowsgui flag, attempts to print output using standard methods such as println or fmt.Println result in nothing being displayed in the command window.

Solution

To print output in this scenario, you need to explicitly attach the process to the console of its parent process. This can be achieved using the AttachConsole API function, which is accessible through the syscall package:

package main

import (
    "fmt"
    "syscall"
)

const (
    ATTACH_PARENT_PROCESS = ^uint32(0) // (DWORD)-1
)

var (
    modkernel32 = syscall.NewLazyDLL("kernel32.dll")

    procAttachConsole = modkernel32.NewProc("AttachConsole")

)

func AttachConsole(dwParentProcess uint32) (ok bool) {
    r0, _, _ := syscall.Syscall(procAttachConsole.Addr(), 1, uintptr(dwParentProcess), 0, 0)
    ok = bool(r0 != 0)
    return
}

func main() {
    ok := AttachConsole(ATTACH_PARENT_PROCESS)
    if ok {
        fmt.Println("Okay, attached")
    }
}

Call AttachConsole(ATTACH_PARENT_PROCESS) before attempting to print output, which will connect the process to the parent console. After this step, you can use standard printing methods as usual.

Additional Options

If AttachConsole fails, you can consider these alternatives:

• Create a console window with AllocConsole(): This will create a new console window for the process, but may not be ideal for displaying brief information like a version number.
• Use a GUI dialog: Display the information in a graphical user interface dialog box, which can provide a cleaner user experience and associate the information more naturally with the GUI application.

The above is the detailed content of How to Print to the Command Window from a Go GUI Application Compiled with `-ldflags -H=windowsgui`?. For more information, please follow other related articles on the PHP Chinese website!