Added a new function timestamp to get the current time back. Fixes ha…

…shicorp#494

config/interpolate_funcs.go

@@ -5,17 +5,19 @@ import (
 	"fmt"
 	"io/ioutil"
 	"strings"
+	"time"
 )
 
 // Funcs is the mapping of built-in functions for configuration.
 var Funcs map[string]InterpolationFunc
 
 func init() {
 	Funcs = map[string]InterpolationFunc{
-		"concat": interpolationFuncConcat,
-		"file":   interpolationFuncFile,
-		"join":   interpolationFuncJoin,
-		"lookup": interpolationFuncLookup,
+		"concat":    interpolationFuncConcat,
+		"file":      interpolationFuncFile,
+		"join":      interpolationFuncJoin,
+		"lookup":    interpolationFuncLookup,
+		"timestamp": interpolationFuncTimestamp,
 	}
 }
 
@@ -87,3 +89,21 @@ func interpolationFuncLookup(
 
 	return v, nil
 }
+
+// interpolationFuncTimestamp impelements print out the current date/time
+// using either the given layout or a default of 20060102150405
+func interpolationFuncTimestamp(
+	vs map[string]string, args ...string) (string, error) {
+	if len(args) > 1 {
+		return "", fmt.Errorf("timestamp expects either 0 or 1 argument")
+	}
+
+	v := ""
+	if len(args) == 1 {
+		v = time.Now().Format(args[0])
+	} else {
+		v = time.Now().Format("20060102150405")
+	}
+
+	return v, nil
+}

config/interpolate_funcs_test.go

@@ -189,3 +189,46 @@ func TestInterpolateFuncLookup(t *testing.T) {
 		}
 	}
 }
+
+func TestInterpolateFuncTimestamp(t *testing.T) {
+	cases := []struct {
+		Args   []string
+		Result string
+		Error  bool
+	}{
+		{
+			[]string{},
+			"20060102150405",
+			false,
+		},
+
+		{
+			[]string{"2006-01-02.15_04_05"},
+			"2006-01-02.15_04_05",
+			false,
+		},
+
+		{
+			[]string{"blah"},
+			"blah",
+			false,
+		},
+
+		{
+			[]string{"20060102150405", "20060102150405"},
+			"",
+			true,
+		},
+	}
+
+	for i, tc := range cases {
+		actual, err := interpolationFuncTimestamp(nil, tc.Args...)
+		if (err != nil) != tc.Error {
+			t.Fatalf("%d: err: %s", i, err)
+		}
+
+		if len(actual) != len(tc.Result) {
+			t.Fatalf("%d: bad: %#v", i, actual)
+		}
+	}
+}

website/source/docs/configuration/interpolation.html.md

@@ -74,3 +74,9 @@ The supported built-in functions are:
 
   * `lookup(map, key)` - Performs a dynamic lookup into a mapping
       variable.
+
+  * `timestamp(layout)` - Returns the current time formatted with the given layout.
+      Layout is an optional arguent. The layout is expected to be
+      based on the Go reference time of Mon Jan 2 15:04:05 MST 2006.
+      If no layout is passed, the default layout 20060102150405 is used.
+      Example: `timestamp("2006_01_02-15:04:05")` returns 2014_11_18-12:32:41