Improved by Eric Raymond.

diff --git a/Lib/cmd.py b/Lib/cmd.py
index 857bed127b749f253ac1b3b8b378e8af7427b99c..366b0c95d805c45543c50a7bc1c6a7fcd5c74867 100644 (file)
--- a/Lib/cmd.py
+++ b/Lib/cmd.py
@@ -1,4 +1,39 @@
 # A generic class to build line-oriented command interpreters
+#
+# Interpreters constructed with this class obey the following conventions:
+#
+# 1. End of file on input is processed as the command 'EOF'.
+# 2. A command is parsed out of each line by collecting the prefix composed
+#    of characters in the identchars member.
+# 3. A command `foo' is dispatched to a method 'do_foo()'; the do_ method
+#    is passed a single argument consisting of the remainder of the line.
+# 4. Typing an empty line repeats the last command.  (Actually, it calls the
+#    method `emptyline', which may be overridden in a subclass.)
+# 5. There is a predefined `help' method.  Given an argument `topic', it
+#    calls the command `help_topic'.  With no arguments, it lists all topics
+#    with defined help_ functions, broken into up to three topics; documented
+#    commands, miscellaneous help topics, and undocumented commands.
+# 6. The command '?' is a synonym for `help'.  The command '!' is a synonym
+#    for `shell', if a do_shell method exists.
+#
+# The `default' method may be overridden to intercept commands for which there
+# is no do_ method.
+#
+# The data member `self.ruler' sets the character used to draw separator lines
+# in the help messages.  If empty, no ruler line is drawn.  It defaults to "=".
+#
+# If the value of `self.intro' is nonempty when the cmdloop method is called,
+# it is printed out on interpreter startup.  This value may be overridden
+# via an optional argument to the cmdloop() method.
+#
+# The data members `self.doc_header', `self.misc_header', and
+# `self.undoc_header' set the headers used for the help function's
+# listings of documented functions, miscellaneous topics, and undocumented
+# functions respectively.
+#
+# These interpreters use raw_input; thus, if the readline module is loaded,
+# they automatically support Emacs-like command history and editing features.
+#
 
 import string
 import sys
@@ -8,27 +43,58 @@ PROMPT = '(Cmd) '
 IDENTCHARS = string.letters + string.digits + '_'
 
 class Cmd:
+       prompt = PROMPT
+       identchars = IDENTCHARS
+       ruler = '='
+       lastcmd = ''
+       intro = None
+       doc_header = "Documented commands (type help <topic>):"
+       misc_header = "Miscellaneous help topics:"
+       undoc_header = "Undocumented commands:"
 
-       def __init__(self):
-               self.prompt = PROMPT
-               self.identchars = IDENTCHARS
-               self.lastcmd = ''
-
-       def cmdloop(self):
+       def cmdloop(self, intro=None):
+               self.preloop()
+               if intro != None:
+                       self.intro = intro
+               if self.intro:
+                       print self.intro
                stop = None
                while not stop:
                        try:
                                line = raw_input(self.prompt)
                        except EOFError:
                                line = 'EOF'
+                       self.precmd()
                        stop = self.onecmd(line)
+                       self.postcmd()
+               self.postloop()
+
+       def precmd(self):
+               pass
+
+       def postcmd(self):
+               pass
+
+       def preloop(self):
+               pass
+
+       def postloop(self):
+               pass
 
        def onecmd(self, line):
                line = string.strip(line)
-               if not line:
-                       line = self.lastcmd
-               else:
-                       self.lastcmd = line
+               if line == '?':
+                       line = 'help'
+               elif line == '!':
+                       if hasattr(self, 'do_shell'):
+                               line = 'shell'
+                       else:
+                               self.default(line)
+                               return
+               elif not line:
+                       self.emptyline()
+                       return
+               self.lastcmd = line
                i, n = 0, len(line)
                while i < n and line[i] in self.identchars: i = i+1
                cmd, arg = line[:i], string.strip(line[i:])
@@ -41,6 +107,9 @@ class Cmd:
                                return self.default(line)
                        return func(arg)
 
+       def emptyline(self):
+               return self.onecmd(self.lastcmd)
+
        def default(self, line):
                print '*** Unknown syntax:', line
 
@@ -70,17 +139,15 @@ class Cmd:
                                        else:
                                                cmds_undoc.append(cmd)
                        print 
-                       self.print_topics("Documented commands (type help " \
-                                         "<topic>):",cmds_doc, 15, 80)
-                       self.print_topics("Miscellaneous help topics:",
-                                         help.keys(), 15, 80)
-                       self.print_topics("Undocumented commands:", 
-                                         cmds_undoc, 15, 80)
+                       self.print_topics(self.doc_header,   cmds_doc,   15,80)
+                       self.print_topics(self.misc_header,  help.keys(),15,80)
+                       self.print_topics(self.undoc_header, cmds_undoc, 15,80)
 
        def print_topics(self, header, cmds, cmdlen, maxcol):
                if cmds:
                        print header;
-                       print "="*len(header)
+                       if self.ruler:
+                           print self.ruler * len(header)
                        (cmds_per_line,junk)=divmod(maxcol,cmdlen)
                        col=cmds_per_line
                        for cmd in cmds: