diff --git a/Std.lean b/Std.lean
index 4e2455a0e8..a1a8acb639 100644
--- a/Std.lean
+++ b/Std.lean
@@ -141,6 +141,7 @@ import Std.Tactic.RCases
 import Std.Tactic.Relation.Rfl
 import Std.Tactic.Relation.Symm
 import Std.Tactic.Replace
+import Std.Tactic.RunCmd
 import Std.Tactic.SeqFocus
 import Std.Tactic.ShowTerm
 import Std.Tactic.SimpTrace
diff --git a/Std/Tactic/RunCmd.lean b/Std/Tactic/RunCmd.lean
new file mode 100644
index 0000000000..2308b30378
--- /dev/null
+++ b/Std/Tactic/RunCmd.lean
@@ -0,0 +1,61 @@
+/-
+Copyright (c) 2018 Sebastian Ullrich. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Sebastian Ullrich, Mario Carneiro
+-/
+import Lean.Elab.Eval
+import Std.Util.TermUnsafe
+
+/-!
+Defines commands to compile and execute a command / term / tactic on the spot:
+
+* `run_cmd doSeq` command which executes code in `CommandElabM Unit`.
+  This is almost the same as `#eval show CommandElabM Unit from do doSeq`,
+  except that it doesn't print an empty diagnostic.
+
+* `run_tac doSeq` tactic which executes code in `TacticM Unit`.
+
+* `by_elab doSeq` term which executes code in `TermElabM Expr` to produce an expression.
+-/
+
+namespace Std.Tactic.RunCmd
+open Lean Meta Elab Command Term Tactic
+
+/--
+The `run_cmd doSeq` command executes code in `CommandElabM Unit`.
+This is almost the same as `#eval show CommandElabM Unit from do doSeq`,
+except that it doesn't print an empty diagnostic.
+-/
+elab (name := runCmd) "run_cmd " elems:doSeq : command => do
+  ← liftTermElabM <|
+    unsafe evalTerm (CommandElabM Unit)
+      (mkApp (mkConst ``CommandElabM) (mkConst ``Unit))
+      (← `(discard do $elems))
+
+/-- The `run_tac doSeq` tactic executes code in `TacticM Unit`. -/
+elab (name := runTac) "run_tac " e:doSeq : tactic => do
+  ← unsafe evalTerm (TacticM Unit) (mkApp (mkConst ``TacticM) (mkConst ``Unit))
+    (← `(discard do $e))
+
+/--
+* The `by_elab doSeq` expression runs the `doSeq` as a `TermElabM Expr` to
+  synthesize the expression.
+* `by_elab fun expectedType? => do doSeq` receives the expected type (an `Option Expr`)
+  as well.
+-/
+syntax (name := byElab) "by_elab " doSeq : term
+
+/-- Elaborator for `by_elab`. -/
+@[term_elab byElab] def elabRunElab : TermElab := fun
+| `(by_elab $cmds:doSeq), expectedType? => do
+  if let `(Lean.Parser.Term.doSeq| $e:term) := cmds then
+    if e matches `(Lean.Parser.Term.doSeq| fun $[$_args]* => $_) then
+      let tac ← unsafe evalTerm
+        (Option Expr → TermElabM Expr)
+        (Lean.mkForall `x .default
+          (mkApp (mkConst ``Option) (mkConst ``Expr))
+          (mkApp (mkConst ``TermElabM) (mkConst ``Expr))) e
+      return ← tac expectedType?
+  (← unsafe evalTerm (TermElabM Expr) (mkApp (mkConst ``TermElabM) (mkConst ``Expr))
+    (← `(do $cmds)))
+| _, _ => throwUnsupportedSyntax
diff --git a/test/run_cmd.lean b/test/run_cmd.lean
new file mode 100644
index 0000000000..eeefab07d7
--- /dev/null
+++ b/test/run_cmd.lean
@@ -0,0 +1,16 @@
+import Lean.Elab.Tactic.ElabTerm
+import Std.Tactic.RunCmd
+import Std.Tactic.GuardMsgs
+
+open Lean Elab Tactic
+
+/-- info: hello world -/
+#guard_msgs in
+run_cmd logInfo m!"hello world"
+
+example : True := by
+  run_tac
+    evalApplyLikeTactic MVarId.apply (← `(True.intro))
+
+example : True := by_elab
+  Term.elabTerm (← `(True.intro)) none