first test compiles, will need testing and additional tests

Author: vsoch

cmd/diff.go

@@ -158,7 +158,11 @@ func diffFile(image1, image2 *pkgutil.Image) error {
 	if err != nil {
 		return err
 	}
-	util.TemplateOutput(diff, "FilenameDiff")
+	writer, err := getWriter(outputFile)
+	if err != nil {
+		return err
+	}
+	util.TemplateOutput(writer, diff, "FilenameDiff")
 	return nil
 }
 

cmd/root.go

@@ -19,6 +19,7 @@ package cmd
 import (
 	goflag "flag"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	"sort"
@@ -40,6 +41,7 @@ var save bool
 var types diffTypes
 var noCache bool
 
+var outputFile string
 var cacheDir string
 var LogLevel string
 var format string
@@ -70,27 +72,35 @@ Tarballs can also be specified by simply providing the path to the .tar, .tar.gz
 }
 
 func outputResults(resultMap map[string]util.Result) {
+
 	// Outputs diff/analysis results in alphabetical order by analyzer name
 	sortedTypes := []string{}
 	for analyzerType := range resultMap {
 		sortedTypes = append(sortedTypes, analyzerType)
 	}
 	sort.Strings(sortedTypes)
 
+	// Get the writer
+	writer, err := getWriter(outputFile)
+	if err != nil {
+		logrus.Error(err)
+	}
+
 	results := make([]interface{}, len(resultMap))
 	for i, analyzerType := range sortedTypes {
 		result := resultMap[analyzerType]
 		if json {
 			results[i] = result.OutputStruct()
 		} else {
-			err := result.OutputText(analyzerType, format)
+			err := result.OutputText(writer, analyzerType, format)
 			if err != nil {
 				logrus.Error(err)
 			}
 		}
 	}
 	if json {
-		err := util.JSONify(results)
+
+		err := util.JSONify(writer, results)
 		if err != nil {
 			logrus.Error(err)
 		}
@@ -162,6 +172,29 @@ func getCacheDir(imageName string) (string, error) {
 	return filepath.Join(rootDir, filepath.Clean(imageName)), nil
 }
 
+func getWriter(outputFile string) (io.Writer, error) {
+	var err error
+	var outWriter io.Writer
+
+	// If the user specifies an output file, ensure exists
+	if outputFile != "" {
+
+		// The file can't exist, we would overwrite it
+		if _, err := os.Stat(outputFile); !os.IsNotExist(err) {
+			return os.Stdout, errors.Wrap(err, "file exists, will not overwrite")
+		}
+
+		// Otherwise, output file is an io.writer
+		outWriter, err = os.Create(outputFile)
+
+	}
+	// If still doesn't exist, return stdout as the io.Writer
+	if outputFile == "" {
+		outWriter = os.Stdout
+	}
+	return outWriter, err
+}
+
 func init() {
 	RootCmd.PersistentFlags().StringVarP(&LogLevel, "verbosity", "v", "warning", "This flag controls the verbosity of container-diff.")
 	RootCmd.PersistentFlags().StringVarP(&format, "format", "", "", "Format to output diff in.")
@@ -201,5 +234,5 @@ func addSharedFlags(cmd *cobra.Command) {
 	cmd.Flags().BoolVarP(&util.SortSize, "order", "o", false, "Set this flag to sort any file/package results by descending size. Otherwise, they will be sorted by name.")
 	cmd.Flags().BoolVarP(&noCache, "no-cache", "n", false, "Set this to force retrieval of image filesystem on each run.")
 	cmd.Flags().StringVarP(&cacheDir, "cache-dir", "c", "", "cache directory base to create .container-diff (default is $HOME).")
-
+	cmd.Flags().StringVarP(&outputFile, "output", "w", "", "output file to write to (default writes to STDOUT).")
 }

util/analyze_output_utils.go

@@ -19,14 +19,15 @@ package util
 import (
 	"errors"
 	"fmt"
+	"io"
 
 	"github.com/GoogleContainerTools/container-diff/pkg/util"
 	"github.com/sirupsen/logrus"
 )
 
 type Result interface {
 	OutputStruct() interface{}
-	OutputText(resultType string, format string) error
+	OutputText(writer io.Writer, resultType string, format string) error
 }
 
 type AnalyzeResult struct {
@@ -41,14 +42,14 @@ func (r ListAnalyzeResult) OutputStruct() interface{} {
 	return r
 }
 
-func (r ListAnalyzeResult) OutputText(resultType string, format string) error {
+func (r ListAnalyzeResult) OutputText(writer io.Writer, resultType string, format string) error {
 	analysis, valid := r.Analysis.([]string)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type []string")
 		return fmt.Errorf("Could not output %s analysis result", r.AnalyzeType)
 	}
 	r.Analysis = analysis
-	return TemplateOutputFromFormat(r, "ListAnalyze", format)
+	return TemplateOutputFromFormat(writer, r, "ListAnalyze", format)
 
 }
 
@@ -73,7 +74,7 @@ func (r MultiVersionPackageAnalyzeResult) OutputStruct() interface{} {
 	return output
 }
 
-func (r MultiVersionPackageAnalyzeResult) OutputText(resultType string, format string) error {
+func (r MultiVersionPackageAnalyzeResult) OutputText(writer io.Writer, resultType string, format string) error {
 	analysis, valid := r.Analysis.(map[string]map[string]PackageInfo)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type map[string]map[string]PackageInfo")
@@ -91,7 +92,7 @@ func (r MultiVersionPackageAnalyzeResult) OutputText(resultType string, format s
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strAnalysis,
 	}
-	return TemplateOutputFromFormat(strResult, "MultiVersionPackageAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "MultiVersionPackageAnalyze", format)
 }
 
 type SingleVersionPackageAnalyzeResult AnalyzeResult
@@ -115,7 +116,7 @@ func (r SingleVersionPackageAnalyzeResult) OutputStruct() interface{} {
 	return output
 }
 
-func (r SingleVersionPackageAnalyzeResult) OutputText(diffType string, format string) error {
+func (r SingleVersionPackageAnalyzeResult) OutputText(writer io.Writer, diffType string, format string) error {
 	analysis, valid := r.Analysis.(map[string]PackageInfo)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type map[string]PackageInfo")
@@ -133,7 +134,7 @@ func (r SingleVersionPackageAnalyzeResult) OutputText(diffType string, format st
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strAnalysis,
 	}
-	return TemplateOutputFromFormat(strResult, "SingleVersionPackageAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "SingleVersionPackageAnalyze", format)
 }
 
 type SingleVersionPackageLayerAnalyzeResult AnalyzeResult
@@ -173,7 +174,7 @@ func (r SingleVersionPackageLayerAnalyzeResult) OutputStruct() interface{} {
 	return output
 }
 
-func (r SingleVersionPackageLayerAnalyzeResult) OutputText(diffType string, format string) error {
+func (r SingleVersionPackageLayerAnalyzeResult) OutputText(writer io.Writer, diffType string, format string) error {
 	analysis, valid := r.Analysis.(PackageLayerDiff)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type PackageLayerDiff")
@@ -205,7 +206,7 @@ func (r SingleVersionPackageLayerAnalyzeResult) OutputText(diffType string, form
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    analysisOutput,
 	}
-	return TemplateOutputFromFormat(strResult, "SingleVersionPackageLayerAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "SingleVersionPackageLayerAnalyze", format)
 }
 
 type PackageOutput struct {
@@ -263,7 +264,7 @@ func (r FileAnalyzeResult) OutputStruct() interface{} {
 	return r
 }
 
-func (r FileAnalyzeResult) OutputText(analyzeType string, format string) error {
+func (r FileAnalyzeResult) OutputText(writer io.Writer, analyzeType string, format string) error {
 	analysis, valid := r.Analysis.([]util.DirectoryEntry)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type []DirectoryEntry")
@@ -286,7 +287,7 @@ func (r FileAnalyzeResult) OutputText(analyzeType string, format string) error {
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strAnalysis,
 	}
-	return TemplateOutputFromFormat(strResult, "FileAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "FileAnalyze", format)
 }
 
 type FileLayerAnalyzeResult AnalyzeResult
@@ -310,7 +311,7 @@ func (r FileLayerAnalyzeResult) OutputStruct() interface{} {
 	return r
 }
 
-func (r FileLayerAnalyzeResult) OutputText(analyzeType string, format string) error {
+func (r FileLayerAnalyzeResult) OutputText(writer io.Writer, analyzeType string, format string) error {
 	analysis, valid := r.Analysis.([][]util.DirectoryEntry)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type []DirectoryEntry")
@@ -338,7 +339,7 @@ func (r FileLayerAnalyzeResult) OutputText(analyzeType string, format string) er
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strDirectoryEntries,
 	}
-	return TemplateOutputFromFormat(strResult, "FileLayerAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "FileLayerAnalyze", format)
 }
 
 type SizeAnalyzeResult AnalyzeResult
@@ -353,7 +354,7 @@ func (r SizeAnalyzeResult) OutputStruct() interface{} {
 	return r
 }
 
-func (r SizeAnalyzeResult) OutputText(analyzeType string, format string) error {
+func (r SizeAnalyzeResult) OutputText(writer io.Writer, analyzeType string, format string) error {
 	analysis, valid := r.Analysis.([]SizeEntry)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type []SizeEntry")
@@ -371,7 +372,7 @@ func (r SizeAnalyzeResult) OutputText(analyzeType string, format string) error {
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strAnalysis,
 	}
-	return TemplateOutputFromFormat(strResult, "SizeAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "SizeAnalyze", format)
 }
 
 type SizeLayerAnalyzeResult AnalyzeResult
@@ -386,7 +387,7 @@ func (r SizeLayerAnalyzeResult) OutputStruct() interface{} {
 	return r
 }
 
-func (r SizeLayerAnalyzeResult) OutputText(analyzeType string, format string) error {
+func (r SizeLayerAnalyzeResult) OutputText(writer io.Writer, analyzeType string, format string) error {
 	analysis, valid := r.Analysis.([]SizeEntry)
 	if !valid {
 		logrus.Error("Unexpected structure of Analysis.  Should be of type []SizeEntry")
@@ -404,5 +405,5 @@ func (r SizeLayerAnalyzeResult) OutputText(analyzeType string, format string) er
 		AnalyzeType: r.AnalyzeType,
 		Analysis:    strAnalysis,
 	}
-	return TemplateOutputFromFormat(strResult, "SizeLayerAnalyze", format)
+	return TemplateOutputFromFormat(writer, strResult, "SizeLayerAnalyze", format)
 }