Don't ask for confirmation when stdin isn't available (i.e. in the notebook)

Closes gh-1268

IPython/core/history.py

@@ -24,6 +24,7 b' except ImportError:'
 import threading
 
 # Our own packages
+from IPython.core.error import StdinNotImplementedError
 from IPython.config.configurable import Configurable
 from IPython.external.decorator import decorator
 from IPython.testing.skipdoctest import skip_doctest
@@ -797,7 +798,12 b" def magic_history(self, parameter_s = ''):"
         close_at_end = False
     else:
         if os.path.exists(outfname):
-            if not io.ask_yes_no("File %r exists. Overwrite?" % outfname):
+            try:
+                ans = io.ask_yes_no("File %r exists. Overwrite?" % outfname)
+            except StdinNotImplementedError:
+                print("Overwriting file.")
+                ans = True
+            if not ans:
                 print('Aborting.')
                 return
 

IPython/core/magic.py

@@ -45,6 +45,7 b' import IPython'
 from IPython.core import debugger, oinspect
 from IPython.core.error import TryNext
 from IPython.core.error import UsageError
+from IPython.core.error import StdinNotImplementedError
 from IPython.core.fakemodule import FakeModule
 from IPython.core.profiledir import ProfileDir
 from IPython.core.macro import Macro
@@ -988,8 +989,11 b' Currently the magic system has the following functions:\\n"""'
         if 'f' in opts:
             ans = True
         else:
-            ans = self.shell.ask_yes_no(
+            try:
+                ans = self.shell.ask_yes_no(
                 "Once deleted, variables cannot be recovered. Proceed (y/[n])? ", default='n')
+            except StdinNotImplementedError:
+                ans = True
         if not ans:
             print 'Nothing done.'
             return
@@ -1059,9 +1063,12 b' Currently the magic system has the following functions:\\n"""'
         if opts.has_key('f'):
             ans = True
         else:
-            ans = self.shell.ask_yes_no(
+            try:
+                ans = self.shell.ask_yes_no(
                 "Once deleted, variables cannot be recovered. Proceed (y/[n])? ",
                 default='n')
+            except StdinNotImplementedError:
+                ans = True
         if not ans:
             print 'Nothing done.'
             return