ulog: able to omit timestamp

README.md

@@ -25,6 +25,22 @@ log.D.Fmt("the level is %s", "debug")
 log.T.Fmt("the level is %s", "trace")
 ```
 
+### Exclude timestamp
+
+When running under systemd it is nice to not include the redundant timestamp
+directly from the logging package (since journald will already insert one). To
+exclude the timestamp simply set the `ULOG_NOTIMESTAMP` environment variable
+to `true`.
+
+e.g. in a systemd unit file
+
+```
+[Service]
+# ...
+Environment="ULOG_NOTIMESTAMP=true"
+```
+
+
 ### License
 
 The `cattlecloud.net/go/ulog` module is open source under the [BSD-3-Clause](LICENSE) license.

ulog.go

@@ -6,6 +6,7 @@ package ulog
 
 import (
 	"fmt"
+	"os"
 	"strconv"
 	"time"
 )
@@ -21,6 +22,7 @@ const (
 type Log struct {
 	name  string
 	level int
+	short bool
 
 	E Output // error logs
 	W Output // warn logs
@@ -33,14 +35,18 @@ type Output interface {
 	Fmt(string, ...any)
 }
 
-type standard struct {
+type format struct {
 	prefix string
 	name   string
+	short  bool
 }
 
-func (s *standard) Fmt(msg string, args ...any) {
-	now := time.Now().Format("01/02 15:04:05")
-	complete := now + " " + s.prefix + " [" + s.name + "] " + fmt.Sprintf(msg, args...)
+func (s *format) Fmt(msg string, args ...any) {
+	complete := s.prefix + " [" + s.name + "] " + fmt.Sprintf(msg, args...)
+	if !s.short {
+		now := time.Now().Format("01/02 15:04:05")
+		complete = now + " " + complete
+	}
 	fmt.Println(complete)
 }
 
@@ -50,7 +56,11 @@ func (null) Fmt(string, ...any) {
 	// do nothing
 }
 
-func output(name string, minimum, level int) Output {
+func output(name string, short bool, minimum, level int) Output {
+	if level > minimum {
+		return null{}
+	}
+
 	var prefix string
 	switch level {
 	case Error:
@@ -65,31 +75,35 @@ func output(name string, minimum, level int) Output {
 		prefix = "TRACE"
 	}
 
-	if level <= minimum {
-		return &standard{
-			prefix: prefix,
-			name:   name,
-		}
+	return &format{
+		prefix: prefix,
+		name:   name,
+		short:  shorten(short),
 	}
+}
 
-	return null{}
+func shorten(force bool) bool {
+	env := os.Getenv("ULOG_NOTIMESTAMP")
+	v, _ := strconv.ParseBool(env)
+	return v || force
 }
 
 func New(name string, opts ...Option) *Log {
 	log := &Log{
 		name:  name,
 		level: Debug,
+		short: false,
 	}
 
 	for _, opt := range opts {
 		opt(log)
 	}
 
-	log.E = output(name, log.level, Error)
-	log.W = output(name, log.level, Warn)
-	log.I = output(name, log.level, Info)
-	log.D = output(name, log.level, Debug)
-	log.T = output(name, log.level, Trace)
+	log.E = output(name, log.short, log.level, Error)
+	log.W = output(name, log.short, log.level, Warn)
+	log.I = output(name, log.short, log.level, Info)
+	log.D = output(name, log.short, log.level, Debug)
+	log.T = output(name, log.short, log.level, Trace)
 
 	return log
 }
@@ -109,3 +123,7 @@ func SetLevel(value int) Option {
 	}
 	return func(l *Log) { l.level = value }
 }
+
+func SetNoTimestamp() Option {
+	return func(l *Log) { l.short = true }
+}

ulog_test.go

@@ -69,3 +69,12 @@ func Test_SetLevel(t *testing.T) {
 
 	t.Log("complete")
 }
+
+func Test_SetNoTimestamp(t *testing.T) {
+	t.Parallel()
+
+	t.Run("shorten", func(_ *testing.T) {
+		log := New("test-timestamp", SetNoTimestamp())
+		log.I.Fmt("no timestamp here")
+	})
+}