Introduce more context to logging

cmd/roy/roy.go

@@ -27,6 +27,7 @@
 
 	"github.com/richardlehane/siegfried"
 	"github.com/richardlehane/siegfried/internal/chart"
+	"github.com/richardlehane/siegfried/internal/logformatter"
 	"github.com/richardlehane/siegfried/pkg/config"
 	"github.com/richardlehane/siegfried/pkg/core"
 	"github.com/richardlehane/siegfried/pkg/loc"
@@ -116,18 +117,23 @@
       Use a different siegfried home directory.
 `
 
-var discoveredDroidFile string
+func setLogger(utc bool) {
+	lw := new(logformatter.LogWriter)
+	lw.Appname = "roy"
+	lw.UTC = utc
+	log.SetOutput(lw)
+}
 
 func init() {
-	// Retrieve our dynamic defaults.
-	discoveredDroidFile = config.Droid()
+	// format the application logger before all other init.
+	setLogger(true)
 }
 
 var (
 	// BUILD, ADD flag sets
 	build         = flag.NewFlagSet("build | add", flag.ExitOnError)
 	home          = build.String("home", config.Home(), "override the default home directory")
 	droid         = build.String("droid", discoveredDroidFile, "set name/path for DROID signature file")
 	mi            = build.String("mi", "", "set name/path for MIMEInfo signature file")
 	fdd           = build.String("fdd", "", "set name/path for LOC FDD signature file")
 	locfdd        = build.Bool("loc", false, "build a LOC FDD signature file")
@@ -165,7 +171,7 @@
 	// HARVEST
 	harvest                    = flag.NewFlagSet("harvest", flag.ExitOnError)
 	harvestHome                = harvest.String("home", config.Home(), "override the default home directory")
 	harvestDroid               = harvest.String("droid", discoveredDroidFile, "set name/path for DROID signature file")
 	harvestChanges             = harvest.Bool("changes", false, "harvest the latest PRONOM release-notes.xml file")
 	_, htimeout, _, _          = config.HarvestOptions()
 	timeout                    = harvest.Duration("timeout", htimeout, "set duration before timing-out harvesting requests e.g. 120s")
@@ -179,7 +185,7 @@
 	// INSPECT (roy inspect | roy inspect fmt/121 | roy inspect usr/local/mysig.sig | roy inspect 10)
 	inspect         = flag.NewFlagSet("inspect", flag.ExitOnError)
 	inspectHome     = inspect.String("home", config.Home(), "override the default home directory")
 	inspectDroid    = inspect.String("droid", discoveredDroidFile, "set name/path for DROID signature file")
 	inspectReports  = inspect.Bool("reports", false, "build signatures from PRONOM reports (rather than DROID xml)")
 	inspectExtend   = inspect.String("extend", "", "comma separated list of additional signatures")
 	inspectExtendc  = inspect.String("extendc", "", "comma separated list of additional container signatures")
@@ -196,7 +202,7 @@
 	// SETS
 	setsf       = flag.NewFlagSet("sets", flag.ExitOnError)
 	setsHome    = setsf.String("home", config.Home(), "override the default home directory")
 	setsDroid   = setsf.String("droid", discoveredDroidFile, "set name/path for DROID signature file")
 	setsChanges = setsf.Bool("changes", false, "create a pronom-changes.json sets file")
 	setsList    = setsf.String("list", "", "expand comma separated list of format sets")
 
@@ -340,7 +346,7 @@
 func getOptions() []config.Option {
 	opts := []config.Option{}
 	// build options
 	if *droid != discoveredDroidFile {
 		opts = append(opts, config.SetDroid(*droid))
 	}
 	if *container != config.Container() {
@@ -450,7 +456,7 @@
 		opts = append(opts, config.SetVerbose(!*quiet)) // do the opposite, because the flag is quiet and the setting is verbose!
 	}
 	// inspect options
 	if *inspectDroid != discoveredDroidFile {
 		opts = append(opts, config.SetDroid(*inspectDroid))
 	}
 	if *inspectMI != "" {
@@ -493,7 +499,7 @@
 }
 
 func setHarvestOptions() {
 	if *harvestDroid != discoveredDroidFile {
 		config.SetDroid(*harvestDroid)()
 	}
 	if *harvestHome != config.Home() {
@@ -521,7 +527,7 @@
 }
 
 func setSetsOptions() {
 	if *setsDroid != discoveredDroidFile {
 		config.SetDroid(*setsDroid)()
 	}
 	if *setsHome != config.Home() {

cmd/sf/sf.go

@@ -31,6 +31,7 @@ import (
 
 	"github.com/richardlehane/siegfried"
 	"github.com/richardlehane/siegfried/internal/checksum"
+	"github.com/richardlehane/siegfried/internal/logformatter"
 	"github.com/richardlehane/siegfried/internal/logger"
 	"github.com/richardlehane/siegfried/pkg/config"
 	"github.com/richardlehane/siegfried/pkg/core"
@@ -42,6 +43,18 @@ import (
 // defaults
 const maxMulti = 1024
 
+func setLogger(utc bool) {
+	lw := new(logformatter.LogWriter)
+	lw.Appname = "sf"
+	lw.UTC = utc
+	log.SetOutput(lw)
+}
+
+func init() {
+	// format the application logger before all other init.
+	setLogger(true)
+}
+
 // flags
 var (
 	updateShort    = flag.Bool("u", false, "update or install the default signature file")

internal/logformatter/log.go

@@ -0,0 +1,39 @@
+package logformatter
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+type LogWriter struct {
+	Appname string
+	UTC     bool
+}
+
+const logTimeFormat = "2006-01-02 15:04:05"
+
+// Write enables us to format a logging prefix for the application. The
+// text will appear before the log message output by the caller.
+//
+// e.g.
+//
+//	`// 2023-11-27 11:36:57 ERROR :: golang-app:100:main() :: this is an error message, ...some diagnosis`
+func (lw *LogWriter) Write(logString []byte) (int, error) {
+	logTime := time.Now().UTC().Format(logTimeFormat)
+	if !lw.UTC {
+		logTime = time.Now().Format(logTimeFormat)
+	}
+	return fmt.Fprintf(os.Stderr, "%s :: %s :: %s",
+		logTime,
+		lw.Appname,
+		string(logString),
+	)
+}
+
+func init() {
+	// Configure logging to use a custom log writer with sensible defaults.
+	log.SetFlags(0 | log.Lshortfile | log.LUTC)
+	log.SetOutput(new(LogWriter))
+}