Lib/cmd.py

   1 """A generic class to build line-oriented command interpreters.
   2
   3 Interpreters constructed with this class obey the following conventions:
   4
   5 1. End of file on input is processed as the command 'EOF'.
   6 2. A command is parsed out of each line by collecting the prefix composed
   7    of characters in the identchars member.
   8 3. A command `foo' is dispatched to a method 'do_foo()'; the do_ method
   9    is passed a single argument consisting of the remainder of the line.
  10 4. Typing an empty line repeats the last command.  (Actually, it calls the
  11    method `emptyline', which may be overridden in a subclass.)
  12 5. There is a predefined `help' method.  Given an argument `topic', it
  13    calls the command `help_topic'.  With no arguments, it lists all topics
  14    with defined help_ functions, broken into up to three topics; documented
  15    commands, miscellaneous help topics, and undocumented commands.
  16 6. The command '?' is a synonym for `help'.  The command '!' is a synonym
  17    for `shell', if a do_shell method exists.
  18 7. If completion is enabled, completing commands will be done automatically,
  19    and completing of commands args is done by calling complete_foo() with
  20    arguments text, line, begidx, endidx.  text is string we are matching
  21    against, all returned matches must begin with it.  line is the current
  22    input line (lstripped), begidx and endidx are the beginning and end
  23    indexes of the text being matched, which could be used to provide
  24    different completion depending upon which position the argument is in.
  25
  26 The `default' method may be overridden to intercept commands for which there
  27 is no do_ method.
  28
  29 The `completedefault' method may be overridden to intercept completions for
  30 commands that have no complete_ method.
  31
  32 The data member `self.ruler' sets the character used to draw separator lines
  33 in the help messages.  If empty, no ruler line is drawn.  It defaults to "=".
  34
  35 If the value of `self.intro' is nonempty when the cmdloop method is called,
  36 it is printed out on interpreter startup.  This value may be overridden
  37 via an optional argument to the cmdloop() method.
  38
  39 The data members `self.doc_header', `self.misc_header', and
  40 `self.undoc_header' set the headers used for the help function's
  41 listings of documented functions, miscellaneous topics, and undocumented
  42 functions respectively.
  43
  44 These interpreters use raw_input; thus, if the readline module is loaded,
  45 they automatically support Emacs-like command history and editing features.
  46 """
  47
  48 import string
  49
  50 __all__ = ["Cmd"]
  51
  52 PROMPT = '(Cmd) '
  53 IDENTCHARS = string.ascii_letters + string.digits + '_'
  54
  55 class Cmd:
  56     """A simple framework for writing line-oriented command interpreters.
  57
  58     These are often useful for test harnesses, administrative tools, and
  59     prototypes that will later be wrapped in a more sophisticated interface.
  60
  61     A Cmd instance or subclass instance is a line-oriented interpreter
  62     framework.  There is no good reason to instantiate Cmd itself; rather,
  63     it's useful as a superclass of an interpreter class you define yourself
  64     in order to inherit Cmd's methods and encapsulate action methods.
  65
  66     """
  67     prompt = PROMPT
  68     identchars = IDENTCHARS
  69     ruler = '='
  70     lastcmd = ''
  71     intro = None
  72     doc_leader = ""
  73     doc_header = "Documented commands (type help <topic>):"
  74     misc_header = "Miscellaneous help topics:"
  75     undoc_header = "Undocumented commands:"
  76     nohelp = "*** No help on %s"
  77     use_rawinput = 1
  78
  79     def __init__(self, completekey='tab', stdin=None, stdout=None):
  80         """Instantiate a line-oriented interpreter framework.
  81
  82         The optional argument 'completekey' is the readline name of a
  83         completion key; it defaults to the Tab key. If completekey is
  84         not None and the readline module is available, command completion
  85         is done automatically. The optional arguments stdin and stdout
  86         specify alternate input and output file objects; if not specified,
  87         sys.stdin and sys.stdout are used.
  88
  89         """
  90         import sys
  91         if stdin is not None:
  92             self.stdin = stdin
  93         else:
  94             self.stdin = sys.stdin
  95         if stdout is not None:
  96             self.stdout = stdout
  97         else:
  98             self.stdout = sys.stdout
  99         self.cmdqueue = []
 100         self.completekey = completekey
 101
 102     def cmdloop(self, intro=None):
 103         """Repeatedly issue a prompt, accept input, parse an initial prefix
 104         off the received input, and dispatch to action methods, passing them
 105         the remainder of the line as argument.
 106
 107         """
 108
 109         self.preloop()
 110         if self.use_rawinput and self.completekey:
 111             try:
 112                 import readline
 113                 self.old_completer = readline.get_completer()
 114                 readline.set_completer(self.complete)
 115                 readline.parse_and_bind(self.completekey+": complete")
 116             except ImportError:
 117                 pass
 118         try:
 119             if intro is not None:
 120                 self.intro = intro
 121             if self.intro:
 122                 self.stdout.write(str(self.intro)+"\n")
 123             stop = None
 124             while not stop:
 125                 if self.cmdqueue:
 126                     line = self.cmdqueue.pop(0)
 127                 else:
 128                     if self.use_rawinput:
 129                         try:
 130                             line = raw_input(self.prompt)
 131                         except EOFError:
 132                             line = 'EOF'
 133                     else:
 134                         self.stdout.write(self.prompt)
 135                         self.stdout.flush()
 136                         line = self.stdin.readline()
 137                         if not len(line):
 138                             line = 'EOF'
 139                         else:
 140                             line = line[:-1] # chop \n
 141                 line = self.precmd(line)
 142                 stop = self.onecmd(line)
 143                 stop = self.postcmd(stop, line)
 144             self.postloop()
 145         finally:
 146             if self.use_rawinput and self.completekey:
 147                 try:
 148                     import readline
 149                     readline.set_completer(self.old_completer)
 150                 except ImportError:
 151                     pass
 152
 153
 154     def precmd(self, line):
 155         """Hook method executed just before the command line is
 156         interpreted, but after the input prompt is generated and issued.
 157
 158         """
 159         return line
 160
 161     def postcmd(self, stop, line):
 162         """Hook method executed just after a command dispatch is finished."""
 163         return stop
 164
 165     def preloop(self):
 166         """Hook method executed once when the cmdloop() method is called."""
 167         pass
 168
 169     def postloop(self):
 170         """Hook method executed once when the cmdloop() method is about to
 171         return.
 172
 173         """
 174         pass
 175
 176     def parseline(self, line):
 177         """Parse the line into a command name and a string containing
 178         the arguments.  Returns a tuple containing (command, args, line).
 179         'command' and 'args' may be None if the line couldn't be parsed.
 180         """
 181         line = line.strip()
 182         if not line:
 183             return None, None, line
 184         elif line[0] == '?':
 185             line = 'help ' + line[1:]
 186         elif line[0] == '!':
 187             if hasattr(self, 'do_shell'):
 188                 line = 'shell ' + line[1:]
 189             else:
 190                 return None, None, line
 191         i, n = 0, len(line)
 192         while i < n and line[i] in self.identchars: i = i+1
 193         cmd, arg = line[:i], line[i:].strip()
 194         return cmd, arg, line
 195
 196     def onecmd(self, line):
 197         """Interpret the argument as though it had been typed in response
 198         to the prompt.
 199
 200         This may be overridden, but should not normally need to be;
 201         see the precmd() and postcmd() methods for useful execution hooks.
 202         The return value is a flag indicating whether interpretation of
 203         commands by the interpreter should stop.
 204
 205         """
 206         cmd, arg, line = self.parseline(line)
 207         if not line:
 208             return self.emptyline()
 209         if cmd is None:
 210             return self.default(line)
 211         self.lastcmd = line
 212         if cmd == '':
 213             return self.default(line)
 214         else:
 215             try:
 216                 func = getattr(self, 'do_' + cmd)
 217             except AttributeError:
 218                 return self.default(line)
 219             return func(arg)
 220
 221     def emptyline(self):
 222         """Called when an empty line is entered in response to the prompt.
 223
 224         If this method is not overridden, it repeats the last nonempty
 225         command entered.
 226
 227         """
 228         if self.lastcmd:
 229             return self.onecmd(self.lastcmd)
 230
 231     def default(self, line):
 232         """Called on an input line when the command prefix is not recognized.
 233
 234         If this method is not overridden, it prints an error message and
 235         returns.
 236
 237         """
 238         self.stdout.write('*** Unknown syntax: %s\n'%line)
 239
 240     def completedefault(self, *ignored):
 241         """Method called to complete an input line when no command-specific
 242         complete_*() method is available.
 243
 244         By default, it returns an empty list.
 245
 246         """
 247         return []
 248
 249     def completenames(self, text, *ignored):
 250         dotext = 'do_'+text
 251         return [a[3:] for a in self.get_names() if a.startswith(dotext)]
 252
 253     def complete(self, text, state):
 254         """Return the next possible completion for 'text'.
 255
 256         If a command has not been entered, then complete against command list.
 257         Otherwise try to call complete_<command> to get list of completions.
 258         """
 259         if state == 0:
 260             import readline
 261             origline = readline.get_line_buffer()
 262             line = origline.lstrip()
 263             stripped = len(origline) - len(line)
 264             begidx = readline.get_begidx() - stripped
 265             endidx = readline.get_endidx() - stripped
 266             if begidx>0:
 267                 cmd, args, foo = self.parseline(line)
 268                 if cmd == '':
 269                     compfunc = self.completedefault
 270                 else:
 271                     try:
 272                         compfunc = getattr(self, 'complete_' + cmd)
 273                     except AttributeError:
 274                         compfunc = self.completedefault
 275             else:
 276                 compfunc = self.completenames
 277             self.completion_matches = compfunc(text, line, begidx, endidx)
 278         try:
 279             return self.completion_matches[state]
 280         except IndexError:
 281             return None
 282
 283     def get_names(self):
 284         # Inheritance says we have to look in class and
 285         # base classes; order is not important.
 286         names = []
 287         classes = [self.__class__]
 288         while classes:
 289             aclass = classes.pop(0)
 290             if aclass.__bases__:
 291                 classes = classes + list(aclass.__bases__)
 292             names = names + dir(aclass)
 293         return names
 294
 295     def complete_help(self, *args):
 296         return self.completenames(*args)
 297
 298     def do_help(self, arg):
 299         if arg:
 300             # XXX check arg syntax
 301             try:
 302                 func = getattr(self, 'help_' + arg)
 303             except AttributeError:
 304                 try:
 305                     doc=getattr(self, 'do_' + arg).__doc__
 306                     if doc:
 307                         self.stdout.write("%s\n"%str(doc))
 308                         return
 309                 except AttributeError:
 310                     pass
 311                 self.stdout.write("%s\n"%str(self.nohelp % (arg,)))
 312                 return
 313             func()
 314         else:
 315             names = self.get_names()
 316             cmds_doc = []
 317             cmds_undoc = []
 318             help = {}
 319             for name in names:
 320                 if name[:5] == 'help_':
 321                     help[name[5:]]=1
 322             names.sort()
 323             # There can be duplicates if routines overridden
 324             prevname = ''
 325             for name in names:
 326                 if name[:3] == 'do_':
 327                     if name == prevname:
 328                         continue
 329                     prevname = name
 330                     cmd=name[3:]
 331                     if cmd in help:
 332                         cmds_doc.append(cmd)
 333                         del help[cmd]
 334                     elif getattr(self, name).__doc__:
 335                         cmds_doc.append(cmd)
 336                     else:
 337                         cmds_undoc.append(cmd)
 338             self.stdout.write("%s\n"%str(self.doc_leader))
 339             self.print_topics(self.doc_header,   cmds_doc,   15,80)
 340             self.print_topics(self.misc_header,  help.keys(),15,80)
 341             self.print_topics(self.undoc_header, cmds_undoc, 15,80)
 342
 343     def print_topics(self, header, cmds, cmdlen, maxcol):
 344         if cmds:
 345             self.stdout.write("%s\n"%str(header))
 346             if self.ruler:
 347                 self.stdout.write("%s\n"%str(self.ruler * len(header)))
 348             self.columnize(cmds, maxcol-1)
 349             self.stdout.write("\n")
 350
 351     def columnize(self, list, displaywidth=80):
 352         """Display a list of strings as a compact set of columns.
 353
 354         Each column is only as wide as necessary.
 355         Columns are separated by two spaces (one was not legible enough).
 356         """
 357         if not list:
 358             self.stdout.write("<empty>\n")
 359             return
 360         nonstrings = [i for i in range(len(list))
 361                         if not isinstance(list[i], str)]
 362         if nonstrings:
 363             raise TypeError, ("list[i] not a string for i in %s" %
 364                               ", ".join(map(str, nonstrings)))
 365         size = len(list)
 366         if size == 1:
 367             self.stdout.write('%s\n'%str(list[0]))
 368             return
 369         # Try every row count from 1 upwards
 370         for nrows in range(1, len(list)):
 371             ncols = (size+nrows-1) // nrows
 372             colwidths = []
 373             totwidth = -2
 374             for col in range(ncols):
 375                 colwidth = 0
 376                 for row in range(nrows):
 377                     i = row + nrows*col
 378                     if i >= size:
 379                         break
 380                     x = list[i]
 381                     colwidth = max(colwidth, len(x))
 382                 colwidths.append(colwidth)
 383                 totwidth += colwidth + 2
 384                 if totwidth > displaywidth:
 385                     break
 386             if totwidth <= displaywidth:
 387                 break
 388         else:
 389             nrows = len(list)
 390             ncols = 1
 391             colwidths = [0]
 392         for row in range(nrows):
 393             texts = []
 394             for col in range(ncols):
 395                 i = row + nrows*col
 396                 if i >= size:
 397                     x = ""
 398                 else:
 399                     x = list[i]
 400                 texts.append(x)
 401             while texts and not texts[-1]:
 402                 del texts[-1]
 403             for col in range(len(texts)):
 404                 texts[col] = texts[col].ljust(colwidths[col])
 405             self.stdout.write("%s\n"%str("  ".join(texts)))