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