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401 lines
14 KiB
Python
401 lines
14 KiB
Python
"""A generic class to build line-oriented command interpreters.
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Interpreters constructed with this class obey the following conventions:
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1. End of file on input is processed as the command 'EOF'.
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2. A command is parsed out of each line by collecting the prefix composed
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of characters in the identchars member.
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3. A command `foo' is dispatched to a method 'do_foo()'; the do_ method
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is passed a single argument consisting of the remainder of the line.
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4. Typing an empty line repeats the last command. (Actually, it calls the
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method `emptyline', which may be overridden in a subclass.)
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5. There is a predefined `help' method. Given an argument `topic', it
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calls the command `help_topic'. With no arguments, it lists all topics
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with defined help_ functions, broken into up to three topics; documented
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commands, miscellaneous help topics, and undocumented commands.
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6. The command '?' is a synonym for `help'. The command '!' is a synonym
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for `shell', if a do_shell method exists.
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7. If completion is enabled, completing commands will be done automatically,
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and completing of commands args is done by calling complete_foo() with
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arguments text, line, begidx, endidx. text is string we are matching
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against, all returned matches must begin with it. line is the current
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input line (lstripped), begidx and endidx are the beginning and end
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indexes of the text being matched, which could be used to provide
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different completion depending upon which position the argument is in.
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The `default' method may be overridden to intercept commands for which there
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is no do_ method.
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The `completedefault' method may be overridden to intercept completions for
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commands that have no complete_ method.
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The data member `self.ruler' sets the character used to draw separator lines
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in the help messages. If empty, no ruler line is drawn. It defaults to "=".
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If the value of `self.intro' is nonempty when the cmdloop method is called,
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it is printed out on interpreter startup. This value may be overridden
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via an optional argument to the cmdloop() method.
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The data members `self.doc_header', `self.misc_header', and
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`self.undoc_header' set the headers used for the help function's
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listings of documented functions, miscellaneous topics, and undocumented
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functions respectively.
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These interpreters use raw_input; thus, if the readline module is loaded,
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they automatically support Emacs-like command history and editing features.
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"""
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import string
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__all__ = ["Cmd"]
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PROMPT = '(Cmd) '
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IDENTCHARS = string.ascii_letters + string.digits + '_'
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class Cmd:
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"""A simple framework for writing line-oriented command interpreters.
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These are often useful for test harnesses, administrative tools, and
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prototypes that will later be wrapped in a more sophisticated interface.
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A Cmd instance or subclass instance is a line-oriented interpreter
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framework. There is no good reason to instantiate Cmd itself; rather,
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it's useful as a superclass of an interpreter class you define yourself
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in order to inherit Cmd's methods and encapsulate action methods.
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"""
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prompt = PROMPT
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identchars = IDENTCHARS
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ruler = '='
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lastcmd = ''
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intro = None
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doc_leader = ""
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doc_header = "Documented commands (type help <topic>):"
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misc_header = "Miscellaneous help topics:"
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undoc_header = "Undocumented commands:"
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nohelp = "*** No help on %s"
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use_rawinput = 1
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def __init__(self, completekey='tab', stdin=None, stdout=None):
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"""Instantiate a line-oriented interpreter framework.
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The optional argument 'completekey' is the readline name of a
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completion key; it defaults to the Tab key. If completekey is
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not None and the readline module is available, command completion
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is done automatically. The optional arguments stdin and stdout
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specify alternate input and output file objects; if not specified,
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sys.stdin and sys.stdout are used.
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"""
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import sys
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if stdin is not None:
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self.stdin = stdin
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else:
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self.stdin = sys.stdin
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if stdout is not None:
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self.stdout = stdout
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else:
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self.stdout = sys.stdout
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self.cmdqueue = []
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self.completekey = completekey
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def cmdloop(self, intro=None):
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"""Repeatedly issue a prompt, accept input, parse an initial prefix
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off the received input, and dispatch to action methods, passing them
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the remainder of the line as argument.
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"""
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self.preloop()
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if intro is not None:
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self.intro = intro
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if self.intro:
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self.stdout.write(str(self.intro)+"\n")
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stop = None
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while not stop:
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if self.cmdqueue:
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line = self.cmdqueue.pop(0)
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else:
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if self.use_rawinput:
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try:
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line = raw_input(self.prompt)
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except EOFError:
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line = 'EOF'
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else:
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self.stdout.write(self.prompt)
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self.stdout.flush()
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line = self.stdin.readline()
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if not len(line):
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line = 'EOF'
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else:
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line = line[:-1] # chop \n
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line = self.precmd(line)
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stop = self.onecmd(line)
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stop = self.postcmd(stop, line)
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self.postloop()
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def precmd(self, line):
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"""Hook method executed just before the command line is
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interpreted, but after the input prompt is generated and issued.
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"""
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return line
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def postcmd(self, stop, line):
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"""Hook method executed just after a command dispatch is finished."""
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return stop
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def preloop(self):
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"""Hook method executed once when the cmdloop() method is called."""
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if self.completekey:
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try:
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import readline
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self.old_completer = readline.get_completer()
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readline.set_completer(self.complete)
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readline.parse_and_bind(self.completekey+": complete")
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except ImportError:
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pass
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def postloop(self):
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"""Hook method executed once when the cmdloop() method is about to
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return.
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"""
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if self.completekey:
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try:
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import readline
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readline.set_completer(self.old_completer)
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except ImportError:
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pass
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def parseline(self, line):
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"""Parse the line into a command name and a string containing
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the arguments. Returns a tuple containing (command, args, line).
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'command' and 'args' may be None if the line couldn't be parsed.
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"""
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line = line.strip()
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if not line:
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return None, None, line
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elif line[0] == '?':
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line = 'help ' + line[1:]
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elif line[0] == '!':
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if hasattr(self, 'do_shell'):
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line = 'shell ' + line[1:]
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else:
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return None, None, line
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i, n = 0, len(line)
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while i < n and line[i] in self.identchars: i = i+1
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cmd, arg = line[:i], line[i:].strip()
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return cmd, arg, line
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def onecmd(self, line):
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"""Interpret the argument as though it had been typed in response
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to the prompt.
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This may be overridden, but should not normally need to be;
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see the precmd() and postcmd() methods for useful execution hooks.
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The return value is a flag indicating whether interpretation of
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commands by the interpreter should stop.
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"""
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cmd, arg, line = self.parseline(line)
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if not line:
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return self.emptyline()
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if cmd is None:
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return self.default(line)
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self.lastcmd = line
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if cmd == '':
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return self.default(line)
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else:
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try:
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func = getattr(self, 'do_' + cmd)
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except AttributeError:
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return self.default(line)
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return func(arg)
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def emptyline(self):
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"""Called when an empty line is entered in response to the prompt.
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If this method is not overridden, it repeats the last nonempty
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command entered.
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"""
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if self.lastcmd:
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return self.onecmd(self.lastcmd)
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def default(self, line):
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"""Called on an input line when the command prefix is not recognized.
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If this method is not overridden, it prints an error message and
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returns.
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"""
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self.stdout.write('*** Unknown syntax: %s\n'%line)
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def completedefault(self, *ignored):
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"""Method called to complete an input line when no command-specific
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complete_*() method is available.
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By default, it returns an empty list.
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"""
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return []
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def completenames(self, text, *ignored):
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dotext = 'do_'+text
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return [a[3:] for a in self.get_names() if a.startswith(dotext)]
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def complete(self, text, state):
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"""Return the next possible completion for 'text'.
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If a command has not been entered, then complete against command list.
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Otherwise try to call complete_<command> to get list of completions.
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"""
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if state == 0:
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import readline
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origline = readline.get_line_buffer()
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line = origline.lstrip()
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stripped = len(origline) - len(line)
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begidx = readline.get_begidx() - stripped
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endidx = readline.get_endidx() - stripped
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if begidx>0:
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cmd, args, foo = self.parseline(line)
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if cmd == '':
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compfunc = self.completedefault
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else:
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try:
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compfunc = getattr(self, 'complete_' + cmd)
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except AttributeError:
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compfunc = self.completedefault
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else:
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compfunc = self.completenames
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self.completion_matches = compfunc(text, line, begidx, endidx)
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try:
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return self.completion_matches[state]
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except IndexError:
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return None
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def get_names(self):
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# Inheritance says we have to look in class and
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# base classes; order is not important.
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names = []
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classes = [self.__class__]
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while classes:
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aclass = classes.pop(0)
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if aclass.__bases__:
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classes = classes + list(aclass.__bases__)
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names = names + dir(aclass)
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return names
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def complete_help(self, *args):
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return self.completenames(*args)
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def do_help(self, arg):
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if arg:
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# XXX check arg syntax
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try:
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func = getattr(self, 'help_' + arg)
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except AttributeError:
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try:
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doc=getattr(self, 'do_' + arg).__doc__
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if doc:
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self.stdout.write("%s\n"%str(doc))
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return
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except AttributeError:
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pass
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self.stdout.write("%s\n"%str(self.nohelp % (arg,)))
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return
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func()
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else:
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names = self.get_names()
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cmds_doc = []
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cmds_undoc = []
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help = {}
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for name in names:
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if name[:5] == 'help_':
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help[name[5:]]=1
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names.sort()
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# There can be duplicates if routines overridden
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prevname = ''
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for name in names:
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if name[:3] == 'do_':
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if name == prevname:
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continue
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prevname = name
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cmd=name[3:]
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if cmd in help:
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cmds_doc.append(cmd)
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del help[cmd]
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elif getattr(self, name).__doc__:
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cmds_doc.append(cmd)
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else:
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cmds_undoc.append(cmd)
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self.stdout.write("%s\n"%str(self.doc_leader))
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self.print_topics(self.doc_header, cmds_doc, 15,80)
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self.print_topics(self.misc_header, help.keys(),15,80)
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self.print_topics(self.undoc_header, cmds_undoc, 15,80)
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def print_topics(self, header, cmds, cmdlen, maxcol):
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if cmds:
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self.stdout.write("%s\n"%str(header))
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if self.ruler:
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self.stdout.write("%s\n"%str(self.ruler * len(header)))
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self.columnize(cmds, maxcol-1)
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self.stdout.write("\n")
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def columnize(self, list, displaywidth=80):
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"""Display a list of strings as a compact set of columns.
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Each column is only as wide as necessary.
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Columns are separated by two spaces (one was not legible enough).
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"""
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if not list:
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self.stdout.write("<empty>\n")
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return
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nonstrings = [i for i in range(len(list))
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if not isinstance(list[i], str)]
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if nonstrings:
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raise TypeError, ("list[i] not a string for i in %s" %
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", ".join(map(str, nonstrings)))
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size = len(list)
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if size == 1:
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self.stdout.write('%s\n'%str(list[0]))
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return
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# Try every row count from 1 upwards
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for nrows in range(1, len(list)):
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ncols = (size+nrows-1) // nrows
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colwidths = []
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totwidth = -2
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for col in range(ncols):
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colwidth = 0
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for row in range(nrows):
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i = row + nrows*col
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if i >= size:
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break
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x = list[i]
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colwidth = max(colwidth, len(x))
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colwidths.append(colwidth)
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totwidth += colwidth + 2
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if totwidth > displaywidth:
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break
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if totwidth <= displaywidth:
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break
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else:
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nrows = len(list)
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ncols = 1
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colwidths = [0]
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for row in range(nrows):
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texts = []
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for col in range(ncols):
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i = row + nrows*col
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if i >= size:
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x = ""
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else:
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x = list[i]
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texts.append(x)
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while texts and not texts[-1]:
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del texts[-1]
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for col in range(len(texts)):
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texts[col] = texts[col].ljust(colwidths[col])
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self.stdout.write("%s\n"%str(" ".join(texts)))
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