写入ssh.Session.StdinPipe（）已挂起

Question

I'm using go's ssh module, and I'm trying to pipe input from my program to the remote shell over stdin. This works as expected, printing Hello World:

mySession := PrepareSession()  // helper method to prepare a Connection and Session object
output, _ := mySession.Output("echo Hello World")
fmt.Println(output)

When I try to provide stdin input, however, it hangs on the line myStdin.Write("Hello World") (I've confirmed this with a debugger):

mySession := PrepareSession()
myStdin, _ := mySession.StdinPipe()
myStdin.Write("Hello World")
output, _ := mySession.Output("cat /dev/stdin | echo")
fmt.Println(output)

Replacing myStdin.Write("Hello World") with fmt.Fprint(myStdin, "Hello World") yields the same problem.

Overall I just don't understand how pipes work in Go - how do I get the pipe to stop hanging when I feed input to it?

Answer 1

StdinPipe is the standard input for the remote command, as mentioned in the docs.

Your second example attempts to write to stdin on the remote host without running a command. Since there is no remote command, there is no consumer for stdin, hanging forever.

Instead, you should do something similar to the Output method:

func (s *Session) Output(cmd string) ([]byte, error) {
    if s.Stdout != nil {
        return nil, errors.New("ssh: Stdout already set")
    }
    var b bytes.Buffer
    s.Stdout = &b
    err := s.Run(cmd)  <---- you need to run a command on the remote host.
    return b.Bytes(), err
}