Function ExecContainer

dockerutil/exec.go:29–96

ExecContainer runs a command in a container. It returns the output and any error. If an error occurs during the execution of the command, the output is appended to the error.

(ctx context.Context, client Client, config ExecConfig)

// ExecContainer runs a command in a container. It returns the output and any error.
// If an error occurs during the execution of the command, the output is appended to the error.
func ExecContainer(ctx context.Context, client Client, config ExecConfig) ([]byte, error) {
	exec, err := client.ContainerExecCreate(ctx, config.ContainerID, container.ExecOptions{
		Detach:       config.Detach,
		Cmd:          append([]string{config.Cmd}, config.Args...),
		User:         config.User,
		AttachStderr: true,
		AttachStdout: true,
		AttachStdin:  config.Stdin != nil,
		Env:          config.Env,
	})
	if err != nil {
		return nil, xerrors.Errorf("exec create: %w", err)
	}

	resp, err := client.ContainerExecAttach(ctx, exec.ID, container.ExecAttachOptions{})
	if err != nil {
		return nil, xerrors.Errorf("attach to exec: %w", err)
	}
	defer resp.Close()

	if config.Stdin != nil {
		_, err = io.Copy(resp.Conn, config.Stdin)
		if err != nil {
			return nil, xerrors.Errorf("copy stdin: %w", err)
		}
		err = resp.CloseWrite()
		if err != nil {
			return nil, xerrors.Errorf("close write: %w", err)
		}
	}

	var (
		buf bytes.Buffer
		// Avoid capturing too much output. We want to prevent
		// a memory leak. This is especially important when
		// we run the bootstrap script since we do not return.
		psw = &xio.PrefixSuffixWriter{
			W: &buf,
			N: 1 << 10,
		}
		wr io.Writer = psw
	)

	if config.StdOutErr != nil {
		wr = io.MultiWriter(psw, config.StdOutErr)
	}

	_, err = io.Copy(wr, resp.Reader)
	if err != nil {
		return nil, xerrors.Errorf("copy cmd output: %w", err)
	}
	resp.Close()

	inspect, err := client.ContainerExecInspect(ctx, exec.ID)
	if err != nil {
		return nil, xerrors.Errorf("exec inspect: %w", err)
	}