Beginning a shell class
git-svn-id: svn+ssh://localhost/home/henryk/svn/cyberflex-shell/trunk@31 f711b948-2313-0410-aaa9-d29f33439f0b
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henryk
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# -*- coding: iso-8859-1 -*-
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import os, re, binascii, sys, exceptions, traceback, inspect
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try:
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import readline
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except ImportError:
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pass
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class Shell:
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"""This class handles a shell with all the usual goodies: history,
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tab-completion, start-up script. The readline module will be used when
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available to provide some of the functionality."""
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def __init__(self, basename):
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"""Creates a new shell object with the specified basename. The
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basename will be used when constructing the history and start-up script
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filenames: ~/.basename.history and ~/.basenamerc.
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Note that the start-up script will not be called at instantiation time
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but when starting the main-loop. This is so that you can register your
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own commands first."""
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if sys.modules.has_key("readline"):
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histfile = os.path.join(os.environ["HOME"], ".%s.history" % basename)
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try:
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readline.read_history_file(histfile)
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except IOError:
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pass
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import atexit
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atexit.register(readline.write_history_file, histfile)
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del histfile
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readline.parse_and_bind("tab: complete")
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## FIXME basenamerc
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else:
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print >>sys.stderr, "Warning: No readline module available. Most functionality will be missing."
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self._commandsets = [] ## This contains command sets, it's a list of (object, dictionary) tuples
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self.basename = basename
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self.env = {}
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self.register_commands(self)
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def _make_cmdset(target, commands):
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"""Convenience function for code shared between register_commands
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and unregister_commands."""
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if commands is None:
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if isinstance(target, dict):
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new_target = None
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new_commands = target
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elif hasattr(target, "COMMANDS"):
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new_target = target
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new_commands = target.COMMANDS
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else:
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raise TypeError, "target must be either an object with a COMMANDS attribute or a dictionary, not %s" % type(target)
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else:
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if isinstance(commands, dict):
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new_target = target
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new_commands = commands
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else:
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raise TypeError, "commands must be a dictionary, not %s" % type(commandset)
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return (new_target, new_commands)
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_make_cmdset = staticmethod(_make_cmdset)
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def register_commands(self, target, commands=None):
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"""Register an object to provide commands.
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When commands is None or not given then target must either be
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an object with a COMMANDS attribute or a dictionary mapping command
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strings to functions. When commands is given then target can be any
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object and commands must be a dictionary mapping command strings to
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functions."""
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new_commandset = self._make_cmdset(target, commands)
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current_commands = self.get_command_mapping()
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for (command,function) in new_commandset[1].items():
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if not hasattr(function, "__doc__"):
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print >>sys.stderr, "Warning: function %s does not have a docstring, bug author" % function
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old_commandset = current_commands.get(command)
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if old_commandset is not None:
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print >>sys.stderr, "Warning: command '%s' already defined from %s, new definition from %s" % (
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command, old_commandset[0] or "Anonymous list", new_target or "Anonymous list"
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)
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self._commandsets.append( new_commandset )
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def unregister_commands(self, target, command=None):
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"""Unregister an object to provide commands.
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You should provide the same parameters as in the call to
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register_commands()."""
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old_commandset = self._make_cmdset(target, commands)
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return self._commandsets.remove( old_commandset )
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def get_command_mapping(self):
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"""Returns a dictionary that maps commands to their commandsets."""
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commands = {}
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for cmdset in self._commandsets:
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for (command, function) in cmdset[1].items():
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commands[command] = cmdset
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return commands
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def has_command(self, name):
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"""Returns whether this shell knows about a specified command."""
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for cmdset in self._commandsets:
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for (command, function) in cmdset[1].items():
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if command == name:
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return True
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return False
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def help(self, name):
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"""Return a dictionary with help about command named name. The dictionary
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keys are: name, formatted_parameters, description, long_description"""
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for cmdset in self._commandsets:
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for (command, function) in cmdset[1].items():
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if command == name:
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parts = function.__doc__.split("\n", 1)
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if len(parts) != 2:
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parts = [ e.strip() for e in (parts + ["",""])[:2] ]
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(argnames, varargs, varkw, defaults) = \
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inspect.getargspec(function)
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if argnames[0] == "self": ## Any better way?
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argnames = argnames[1:]
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len_mandatory = len(argnames) - \
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len(defaults or [])
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argstring = " ".join(
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[(i < len_mandatory and "%s" or "[%s]")
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% argnames[i] for i in range(len(argnames))]
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)
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return { "name": command,
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"formatted_parameters": argstring,
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"description": parts[0],
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"long_description": parts[1]
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}
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raise ValueError, "No such command '%s'" % name
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def cmd_exit(self):
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"Exit the shell."
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sys.exit(0)
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def cmd_set(self, name=None, value=None):
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"Set a variable or print current settings."
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SHORT_HELP_FORMATSTRING = "%(name)-20s %(description)s"
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LONG_HELP_FORMATSTRING = "%(description)s\nSynopsis: %(name)s %(formatted_parameters)s\n%(long_description)s"
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def cmd_help(self, command=None):
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"Print help, either for all commands or for a specific one."
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if command is None:
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command_list = self.get_command_mapping().keys()
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for command in command_list:
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print self.SHORT_HELP_FORMATSTRING % self.help(command)
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else:
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if self.has_command(command):
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print self.LONG_HELP_FORMATSTRING % self.help(command)
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else:
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print "No such command '%s'" % command
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COMMANDS = {
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"exit": cmd_exit,
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"set": cmd_set,
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"help": cmd_help
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}
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if __name__ == "__main__":
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s = Shell("foobar")
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