added generic user lookup and foreground processes

lookup.go

@@ -0,0 +1,29 @@
+// Copyright (C) 2017 Marius Schellenberger
+
+package godrop
+
+import "strconv"
+
+func atoi(a string) (int, error) {
+	i, err := strconv.Atoi(a)
+	if err != nil {
+		return -1, err
+	}
+	return i, nil
+}
+
+func userID(username string) (uid int, err error) {
+	id, err := lookupUID(username)
+	if err != nil {
+		return -1, err
+	}
+	return atoi(id)
+}
+
+func groupID(name string) (int, error) {
+	id, err := lookupGID(name)
+	if err != nil {
+		return -1, err
+	}
+	return atoi(id)
+}