add outfile option

using regular shell redirection has some issues with logrotate that I'm
trying to work around.

randomizr.go

@@ -1,28 +1,52 @@
 package main
 
 import (
-    "fmt"
-    "math/rand"
-    "time"
+	"flag"
+	"fmt"
+	"math/rand"
+	"os"
+	"time"
+)
+
+var (
+	fname string
 )
 
 // generates a pseudorandom string of length n that is composed of alphanumeric
 // characters.
 func randomString(n int) string {
-    var alpha = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
-    buf := make([]byte, n)
-    for i := 0; i < len(buf); i++ {
-        buf[i] = alpha[rand.Intn(len(alpha)-1)]
-    }
-    return string(buf)
+	var alpha = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	buf := make([]byte, n)
+	for i := 0; i < len(buf); i++ {
+		buf[i] = alpha[rand.Intn(len(alpha)-1)]
+	}
+	return string(buf)
+}
+
+func outFile() (*os.File, error) {
+	if fname == "" {
+		return os.Stdout, nil
+	}
+	options := os.O_WRONLY | os.O_APPEND | os.O_CREATE
+	return os.OpenFile(fname, options, 0644)
 }
 
 func main() {
-    for t := range time.Tick(100 * time.Millisecond) {
-        fmt.Printf("%v %v %v\n", t.UnixNano(), randomString(32), randomString(32))
-    }
+	flag.Parse()
+
+	f, err := outFile()
+	if err != nil {
+		fmt.Printf("ERROR: %v\n", err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
+	for t := range time.Tick(100 * time.Millisecond) {
+		fmt.Fprintf(f, "%v %v %v\n", t.UnixNano(), randomString(32), randomString(32))
+	}
 }
 
 func init() {
-    rand.Seed(time.Now().UnixNano())
+	flag.StringVar(&fname, "file", "", "destination file to which random data will be appended")
+	rand.Seed(time.Now().UnixNano())
 }