我们可以将所有控制台日志定向到文件吗？

Question

when running web app locally with command

go run MainPackageFile.go

and we can map logger e.g with martini

m := martini.Classic()
m.Get("/m", func() string {
  return "Hello world!"
})
m.Map(log.New(f, "[martini]", log.LstdFlags))

however what if there is something wrong outside the code, e.g Go not able to download package etc... is there a way to get those go runtime log? when running locally errors will print out onto console. is there a way when running in server, we can have all those log write into text file?

Answer 1

You can use this function to redirect standard error to a file. This will receive tracebacks.

// redirectStderr to the file passed in
func redirectStderr(f *os.File) {
err := syscall.Dup2(int(f.Fd()), int(os.Stderr.Fd()))
    if err != nil {
        log.Fatalf("Failed to redirect stderr to file: %v", err)
    }
}

It only works on linux/mac/unix.

Here is how to do the same thing for windows

var (
    kernel32 = syscall.MustLoadDLL("kernel32.dll")
    procSetStdHandle = kernel32.MustFindProc("SetStdHandle")
)

func setStdHandle(stdhandle int32, handle syscall.Handle) error {
    r0, _, e1 := syscall.Syscall(procSetStdHandle.Addr(), 2, uintptr(stdhandle), uintptr(handle), 0)
    if r0 == 0 {
        if e1 != 0 {
            return error(e1)
        }
        return syscall.EINVAL
    }
    return nil
}

// redirectStderr to the file passed in
func redirectStderr(f *os.File) {
    err := setStdHandle(syscall.STD_ERROR_HANDLE, syscall.Handle(f.Fd()))
    if err != nil {
        log.Fatalf("Failed to redirect stderr to file: %v", err)
    }
}

Original code from minux