stamp.go: solo timestamps or for each line in stdin

stamp.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"os"
+	"time"
+)
+
+const (
+	defaultFormat  = "2006-01-02 15:04:05"
+	filenameFormat = "20060102-150405"
+)
+
+type flags struct {
+	utc      bool
+	filename bool
+	precise  bool
+}
+
+func stamp(format string, f *flags) string {
+	t := time.Now()
+	if f.utc {
+		t = t.UTC()
+	}
+	return t.Format(format)
+}
+
+func getFormat(f *flags) string {
+	var format string
+	if f.filename {
+		format = filenameFormat
+	} else {
+		format = defaultFormat
+	}
+	if f.precise {
+		format += ".000000000"
+	}
+	return format
+}
+
+func main() {
+	f := flags{}
+	flag.BoolVar(&f.utc, "utc", false, "use UTC instead of local time")
+	flag.BoolVar(&f.filename, "filename", false, "use filename friendly format")
+	flag.BoolVar(&f.precise, "precise", false, "include nanoseconds")
+	flag.Parse()
+
+	format := getFormat(&f)
+
+	stat, _ := os.Stdin.Stat()
+	if (stat.Mode() & os.ModeCharDevice) == 0 {
+		scanner := bufio.NewScanner(os.Stdin)
+		for scanner.Scan() {
+			fmt.Println(stamp(format, &f), scanner.Text())
+		}
+		if err := scanner.Err(); err != nil {
+			panic(err)
+		}
+	} else {
+		fmt.Println(stamp(format, &f))
+	}
+}