added a few options

randomizr.go

@@ -9,7 +9,10 @@ import (
 )
 
 var (
-	fname string
+	fname   string
+	fappend bool
+	reopen  bool
+	freq    float64
 )
 
 // generates a pseudorandom string of length n that is composed of alphanumeric
@@ -27,26 +30,68 @@ func outFile() (*os.File, error) {
 	if fname == "" {
 		return os.Stdout, nil
 	}
-	options := os.O_WRONLY | os.O_APPEND | os.O_CREATE
+	options := os.O_WRONLY | os.O_CREATE
+    if fappend {
+        options |= os.O_APPEND
+    } else {
+        options |= os.O_TRUNC
+    }
+
 	return os.OpenFile(fname, options, 0644)
 }
 
-func main() {
-	flag.Parse()
+func reopenWrite(c chan string) {
+	for line := range c {
+		f, err := outFile()
+		if err != nil {
+			fmt.Printf("ERROR: unable to open outfile: %v", err)
+			continue
+		}
+		if _, err := f.WriteString(line); err != nil {
+			fmt.Printf("ERROR: unable to write line: %v", err)
+		}
+		f.Close()
+	}
+}
 
+func regularWrite(c chan string) {
 	f, err := outFile()
 	if err != nil {
-		fmt.Printf("ERROR: %v\n", err)
-		os.Exit(1)
+		fmt.Printf("ERROR: unable to open outfile: %v", err)
+		return
 	}
 	defer f.Close()
 
-	for t := range time.Tick(100 * time.Millisecond) {
-		fmt.Fprintf(f, "%v %v %v\n", t.UnixNano(), randomString(32), randomString(32))
+	for line := range c {
+		if _, err := f.WriteString(line); err != nil {
+			fmt.Printf("ERROR: unable to write line: %v", err)
+		}
+	}
+}
+
+func writeLines(c chan string) {
+	if reopen {
+		go reopenWrite(c)
+	} else {
+		go regularWrite(c)
+	}
+}
+
+func main() {
+	flag.Parse()
+	c := make(chan string)
+
+	writeLines(c)
+
+	for t := range time.Tick(time.Duration(1e9 / freq)) {
+		c <- fmt.Sprintf("%v %v %v\n", t.UnixNano(), randomString(32), randomString(32))
 	}
 }
 
 func init() {
-	flag.StringVar(&fname, "file", "", "destination file to which random data will be appended")
+	flag.StringVar(&fname, "file", "", "destination file to which random data will be written")
+	flag.BoolVar(&fappend, "append", false, "append to file instead of truncating file on open")
+	flag.BoolVar(&reopen, "reopen", false, "reopen file handle on every write instead of using a persistent handle")
+	flag.Float64Var(&freq, "freq", 1, "frequency in hz at which lines will be written")
 	rand.Seed(time.Now().UnixNano())
 }