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 import sys
  40 import linecache
  41
  42 PROMPT = '(Cmd) '
  43 IDENTCHARS = string.letters + string.digits + '_'
  44
  45 class Cmd:
  46         prompt = PROMPT
  47         identchars = IDENTCHARS
  48         ruler = '='
  49         lastcmd = ''
  50         intro = None
  51         doc_header = "Documented commands (type help <topic>):"
  52         misc_header = "Miscellaneous help topics:"
  53         undoc_header = "Undocumented commands:"
  54
  55         def __init__(self): pass
  56
  57         def cmdloop(self, intro=None):
  58                 self.preloop()
  59                 if intro != None:
  60                         self.intro = intro
  61                 if self.intro:
  62                         print self.intro
  63                 stop = None
  64                 while not stop:
  65                         try:
  66                                 line = raw_input(self.prompt)
  67                         except EOFError:
  68                                 line = 'EOF'
  69                         self.precmd()
  70                         stop = self.onecmd(line)
  71                         self.postcmd()
  72                 self.postloop()
  73
  74         def precmd(self):
  75                 pass
  76
  77         def postcmd(self):
  78                 pass
  79
  80         def preloop(self):
  81                 pass
  82
  83         def postloop(self):
  84                 pass
  85
  86         def onecmd(self, line):
  87                 line = string.strip(line)
  88                 if line == '?':
  89                         line = 'help'
  90                 elif line == '!':
  91                         if hasattr(self, 'do_shell'):
  92                                 line = 'shell'
  93                         else:
  94                                 return self.default(line)
  95                 elif not line:
  96                         return self.emptyline()
  97                 self.lastcmd = line
  98                 i, n = 0, len(line)
  99                 while i < n and line[i] in self.identchars: i = i+1
 100                 cmd, arg = line[:i], string.strip(line[i:])
 101                 if cmd == '':
 102                         return self.default(line)
 103                 else:
 104                         try:
 105                                 func = getattr(self, 'do_' + cmd)
 106                         except AttributeError:
 107                                 return self.default(line)
 108                         return func(arg)
 109
 110         def emptyline(self):
 111                 return self.onecmd(self.lastcmd)
 112
 113         def default(self, line):
 114                 print '*** Unknown syntax:', line
 115
 116         def do_help(self, arg):
 117                 if arg:
 118                         # XXX check arg syntax
 119                         try:
 120                                 func = getattr(self, 'help_' + arg)
 121                         except:
 122                                 print '*** No help on', `arg`
 123                                 return
 124                         func()
 125                 else:
 126                         names = dir(self.__class__)
 127                         cmds_doc = []
 128                         cmds_undoc = []
 129                         help = {}
 130                         for name in names:
 131                                 if name[:5] == 'help_':
 132                                         help[name[5:]]=1
 133                         for name in names:
 134                                 if name[:3] == 'do_':
 135                                         cmd=name[3:]
 136                                         if help.has_key(cmd):
 137                                                 cmds_doc.append(cmd)
 138                                                 del help[cmd]
 139                                         else:
 140                                                 cmds_undoc.append(cmd)
 141                         print
 142                         self.print_topics(self.doc_header,   cmds_doc,   15,80)
 143                         self.print_topics(self.misc_header,  help.keys(),15,80)
 144                         self.print_topics(self.undoc_header, cmds_undoc, 15,80)
 145
 146         def print_topics(self, header, cmds, cmdlen, maxcol):
 147                 if cmds:
 148                         print header;
 149                         if self.ruler:
 150                             print self.ruler * len(header)
 151                         (cmds_per_line,junk)=divmod(maxcol,cmdlen)
 152                         col=cmds_per_line
 153                         for cmd in cmds:
 154                                 if col==0: print
 155                                 print (("%-"+`cmdlen`+"s") % cmd),
 156                                 col = (col+1) % cmds_per_line
 157                         print "\n"