Extend nvidia-ctk config command to allow options to be set

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-ctk/config/flags/options.go

@@ -0,0 +1,71 @@
+/**
+# Copyright (c) NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package flags
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// Options stores options for the config commands
+type Options struct {
+	Config  string
+	Output  string
+	InPlace bool
+}
+
+// Validate checks whether the options are valid.
+func (o Options) Validate() error {
+	if o.InPlace && o.Output != "" {
+		return fmt.Errorf("cannot specify both --in-place and --output")
+	}
+
+	return nil
+}
+
+// EnsureOutputFolder creates the output folder if it does not exist.
+// If the output folder is not specified (i.e. output to STDOUT), it is ignored.
+func (o Options) EnsureOutputFolder() error {
+	if o.Output == "" {
+		return nil
+	}
+	if dir := filepath.Dir(o.Output); dir != "" {
+		return os.MkdirAll(dir, 0755)
+	}
+	return nil
+}
+
+// CreateOutput creates the writer for the output.
+func (o Options) CreateOutput() (io.WriteCloser, error) {
+	if o.Output != "" {
+		return os.Create(o.Output)
+	}
+
+	return nullCloser{os.Stdout}, nil
+}
+
+// nullCloser is a writer that does nothing on Close.
+type nullCloser struct {
+	io.Writer
+}
+
+// Close is a no-op for a nullCloser.
+func (d nullCloser) Close() error {
+	return nil
+}