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