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 #
  19 # The `default' method may be overridden to intercept commands for which there
  20 # is no do_ method.
  21 #
  22 # The data member `self.ruler' sets the character used to draw separator lines
  23 # in the help messages.  If empty, no ruler line is drawn.  It defaults to "=".
  24 #
  25 # If the value of `self.intro' is nonempty when the cmdloop method is called,
  26 # it is printed out on interpreter startup.  This value may be overridden
  27 # via an optional argument to the cmdloop() method.
  28 #
  29 # The data members `self.doc_header', `self.misc_header', and
  30 # `self.undoc_header' set the headers used for the help function's
  31 # listings of documented functions, miscellaneous topics, and undocumented
  32 # functions respectively.
  33 #
  34 # These interpreters use raw_input; thus, if the readline module is loaded,
  35 # they automatically support Emacs-like command history and editing features.
  36 #
  37
  38 import string
  39
  40 PROMPT = '(Cmd) '
  41 IDENTCHARS = string.letters + string.digits + '_'
  42
  43 class Cmd:
  44         prompt = PROMPT
  45         identchars = IDENTCHARS
  46         ruler = '='
  47         lastcmd = ''
  48         cmdqueue = []
  49         intro = None
  50         doc_leader = ""
  51         doc_header = "Documented commands (type help <topic>):"
  52         misc_header = "Miscellaneous help topics:"
  53         undoc_header = "Undocumented commands:"
  54         nohelp = "*** No help on %s"
  55
  56         def __init__(self): pass
  57
  58         def cmdloop(self, intro=None):
  59                 self.preloop()
  60                 if intro != None:
  61                         self.intro = intro
  62                 if self.intro:
  63                         print self.intro
  64                 stop = None
  65                 while not stop:
  66                         if self.cmdqueue:
  67                                 line = self.cmdqueue[0]
  68                                 del self.cmdqueue[0]
  69                         else:
  70                                 try:
  71                                         line = raw_input(self.prompt)
  72                                 except EOFError:
  73                                         line = 'EOF'
  74                         line = self.precmd(line)
  75                         stop = self.onecmd(line)
  76                         stop = self.postcmd(stop, line)
  77                 self.postloop()
  78
  79         def precmd(self, line):
  80                 return line
  81
  82         def postcmd(self, stop, line):
  83                 return stop
  84
  85         def preloop(self):
  86                 pass
  87
  88         def postloop(self):
  89                 pass
  90
  91         def onecmd(self, line):
  92                 line = string.strip(line)
  93                 if line == '?':
  94                         line = 'help'
  95                 elif line == '!':
  96                         if hasattr(self, 'do_shell'):
  97                                 line = 'shell'
  98                         else:
  99                                 return self.default(line)
 100                 elif not line:
 101                         return self.emptyline()
 102                 self.lastcmd = line
 103                 i, n = 0, len(line)
 104                 while i < n and line[i] in self.identchars: i = i+1
 105                 cmd, arg = line[:i], string.strip(line[i:])
 106                 if cmd == '':
 107                         return self.default(line)
 108                 else:
 109                         try:
 110                                 func = getattr(self, 'do_' + cmd)
 111                         except AttributeError:
 112                                 return self.default(line)
 113                         return func(arg)
 114
 115         def emptyline(self):
 116                 if self.lastcmd:
 117                         return self.onecmd(self.lastcmd)
 118
 119         def default(self, line):
 120                 print '*** Unknown syntax:', line
 121
 122         def do_help(self, arg):
 123                 if arg:
 124                         # XXX check arg syntax
 125                         try:
 126                                 func = getattr(self, 'help_' + arg)
 127                         except:
 128                                 try:
 129                                         doc=getattr(self, 'do_' + arg).__doc__
 130                                         if doc:
 131                                                 print doc
 132                                                 return
 133                                 except:
 134                                         pass
 135                                 print self.nohelp % (arg,)
 136                                 return
 137                         func()
 138                 else:
 139                         # Inheritance says we have to look in class and
 140                         # base classes; order is not important.
 141                         names = []
 142                         classes = [self.__class__]
 143                         while classes:
 144                                 aclass = classes[0]
 145                                 if aclass.__bases__:
 146                                     classes = classes + list(aclass.__bases__)
 147                                 names = names + dir(aclass)
 148                                 del classes[0]
 149                         cmds_doc = []
 150                         cmds_undoc = []
 151                         help = {}
 152                         for name in names:
 153                                 if name[:5] == 'help_':
 154                                         help[name[5:]]=1
 155                         names.sort()
 156                         # There can be duplicates if routines overridden
 157                         prevname = ''
 158                         for name in names:
 159                                 if name[:3] == 'do_':
 160                                         if name == prevname:
 161                                                 continue
 162                                         prevname = name
 163                                         cmd=name[3:]
 164                                         if help.has_key(cmd):
 165                                                 cmds_doc.append(cmd)
 166                                                 del help[cmd]
 167                                         elif getattr(self, name).__doc__:
 168                                                 cmds_doc.append(cmd)
 169                                         else:
 170                                                 cmds_undoc.append(cmd)
 171                         print self.doc_leader
 172                         self.print_topics(self.doc_header,   cmds_doc,   15,80)
 173                         self.print_topics(self.misc_header,  help.keys(),15,80)
 174                         self.print_topics(self.undoc_header, cmds_undoc, 15,80)
 175
 176         def print_topics(self, header, cmds, cmdlen, maxcol):
 177                 if cmds:
 178                         print header;
 179                         if self.ruler:
 180                             print self.ruler * len(header)
 181                         (cmds_per_line,junk)=divmod(maxcol,cmdlen)
 182                         col=cmds_per_line
 183                         for cmd in cmds:
 184                                 if col==0: print
 185                                 print (("%-"+`cmdlen`+"s") % cmd),
 186                                 col = (col+1) % cmds_per_line
 187                         print "\n"