Merge pull request #45 from python-cmd2/disable_redirection

Added member boolean flag to disable output redirection and piping.

cmd2.py

@@ -502,7 +502,8 @@ class Cmd(cmd.Cmd):
     # Attributes which are NOT dynamically settable at runtime
     _STOP_AND_EXIT = True  # distinguish end of script file from actual exit
     _STOP_SCRIPT_NO_EXIT = -999
-    allow_cli_args = True
+    allow_cli_args = True       # Should arguments passed on the command-line be processed as commands?
+    allow_redirection = True    # Should output redirection and pipes be allowed
     blankLinesAllowed = False
     colorcodes = {'bold': {True: '\x1b[1m', False: '\x1b[22m'},
                   'cyan': {True: '\x1b[36m', False: '\x1b[39m'},
@@ -636,13 +637,12 @@ def colorize(self, val, color):
     def do_cmdenvironment(self, args):
         """Summary report of interactive parameters."""
         self.stdout.write("""
-        Commands are %(casesensitive)scase-sensitive.
-        Commands may be terminated with: %(terminators)s
-        Settable parameters: %(settable)s\n""" %
-                          {'casesensitive': (self.case_insensitive and 'not ') or '',
-                           'terminators': str(self.terminators),
-                           'settable': ' '.join(self.settable)
-                           })
+        Commands are case-sensitive: {}
+        Commands may be terminated with: {}
+        Command-line arguments allowed: {}
+        Output redirection and pipes allowed: {}
+        Settable parameters: {}\n""".format(not self.case_insensitive, str(self.terminators), self.allow_cli_args,
+                                            self.allow_redirection, ' '.join(self.settable)))
 
     def do_help(self, arg):
         """List available commands with "help" or detailed help with "help cmd"."""
@@ -990,15 +990,17 @@ def onecmd_plus_hooks(self, line):
                 if statement.parsed.command not in self.excludeFromHistory:
                     self.history.append(statement.parsed.raw)
                 try:
-                    self.redirect_output(statement)
+                    if self.allow_redirection:
+                        self.redirect_output(statement)
                     timestart = datetime.datetime.now()
                     statement = self.precmd(statement)
                     stop = self.onecmd(statement)
                     stop = self.postcmd(stop, statement)
                     if self.timing:
                         self.pfeedback('Elapsed: %s' % str(datetime.datetime.now() - timestart))
                 finally:
-                    self.restore_output(statement)
+                    if self.allow_redirection:
+                        self.restore_output(statement)
             except EmptyStatement:
                 return 0
             except ValueError as ex:

tests/test_cmd2.py

@@ -198,17 +198,19 @@ def test_base_cmdenvironment(base_app):
     out = run_cmd(base_app, 'cmdenvironment')
     expected = normalize("""
 
-        Commands are not case-sensitive.
+        Commands are case-sensitive: False
         Commands may be terminated with: [';']
+        Command-line arguments allowed: True
+        Output redirection and pipes allowed: True
 """)
-    assert out[:2] == expected[:2]
-    assert out[2].strip().startswith('Settable parameters: ')
+    assert out[:4] == expected[:4]
+    assert out[4].strip().startswith('Settable parameters: ')
 
     # Settable parameters can be listed in any order, so need to validate carefully using unordered sets
     settable_params = {'continuation_prompt', 'default_file_name', 'prompt', 'abbrev', 'quiet', 'case_insensitive',
                        'colors', 'echo', 'timing', 'editor', 'feedback_to_output', 'debug', 'autorun_on_edit',
                        'locals_in_py'}
-    out_params = set(out[2].split("Settable parameters: ")[1].split())
+    out_params = set(out[4].split("Settable parameters: ")[1].split())
     assert settable_params == out_params
 
 
@@ -330,6 +332,21 @@ def test_output_redirection(base_app):
     os.remove(filename)
 
 
+def test_allow_redirection(base_app):
+    # Set allow_redirection to False
+    base_app.allow_redirection = False
+
+    filename = 'test_allow_redirect.txt'
+
+    # Verify output wasn't redirected
+    out = run_cmd(base_app, 'help > {}'.format(filename))
+    expected = normalize(BASE_HELP)
+    assert out == expected
+
+    # Verify that no file got created
+    assert not os.path.exists(filename)
+
+
 @pytest.mark.skipif(sys.platform.startswith('linux') and getpass.getuser() == 'travis',
                     reason="Unit test passes on Ubuntu 16.04 and Debian 8.7, but fails on TravisCI Linux containers")
 def test_input_redirection(base_app, request):