将stderr紧急事件重定向回go中的终端

Question

I'm trying to redirect panic/standard error back to bash terminal with the following go code:

    if err := syscall.Dup2(-1,int(os.Stderr.Fd())); err != nil {
      log.Fatalf("Failed to redirect stderr to bash: %v",err)
    }

But the err gives me a "bad file descriptor", probably because of the -1 I used in the first argument. I chose the value -1 because I found that int(file.(*os.File).Fd()) returned a -1 when file.Close() has been called.

As for what I'm trying to do. Elsewhere in my program, I had called a syscall.Dup2(int(file.Fd()), int(os.Stderr.Fd())), which logs stderr to an external file. But I want stderr to point to bash terminal on occasion.

https://golang.org/pkg/syscall/ Doesn't give a verbose explanation of syscall.Dup2. I started poking around what file.Fd() returns and how it is used, but also didn't fully understand.

Can anyone tell me how to redirect stderr back to bash terminal?

Answer 1

You have to save the original stderr somewhere before overwriting it with your first Dup2. (In general, it’s a bad idea to use the dup2 feature of closing the target, since it can’t report errors therefrom.) Then you can Dup2 that back to int(os.Stderr.Fd()) (aka 2).