Question

我正在尝试使用cmd包在Python中创建一个shell。我想重现“真实” shell（bash，csh等）的行为，也就是说，当您键入命令并且意识到自己在做错时，请执行ctrl + c来获取一个新的干净提示。

我试图捕获SIGINT，然后调用一个只返回的方法，但是它什么也没做。

这是一个示例示例：

#! /usr/bin/python
# -*- coding: utf-8 -*-

from cmd import Cmd
import signal
import sys


class myPrompt(Cmd):

  def do_exit(self, inp):
    """
         Exit the shell
    """
    return True

  def do_test(self):
    print "hello"
    return


p=myPrompt()

def signal_handler(sig, frame):
  print "world"
  p.do_test()
  return

signal.signal(signal.SIGINT, signal_handler)

p.cmdloop()

编辑：

我按照彼得·伍德的建议更改了代码：

#! /usr/bin/python
# -*- coding: utf-8 -*-

from cmd import Cmd
import signal
import sys


class myPrompt(Cmd):

  def do_exit(self, inp):
    """
         Exit the shell
    """
    return True


  def onecmd(self, line):
    try:
      return super().onecmd(line)
    except:
      return False

p=myPrompt()
p.cmdloop()

我收到此错误：

(Cmd) Traceback (most recent call last):
  File "./test2.py", line 41, in <module>
    p.cmdloop()
  File "/usr/lib/python2.7/cmd.py", line 130, in cmdloop
    line = raw_input(self.prompt)
KeyboardInterrupt

Answer 1

我写了您想要的工作版本。您应该覆盖cmdloop类的onecmd和Cmd方法。

我在cmdloop方法中为处理KeyboardInterrupt定义了一个新关键字：

if self.use_rawinput:
    try:
        line = input(self.prompt)
    except EOFError:
        line = "EOF"
    except KeyboardInterrupt:
        line = "ctrl_c"  # You can handle the `KeyboardInterrupt` exception through this keyword.

我已经用onecmd方法处理了这个关键字。如果line变量包含此关键字，则该方法会将\n写入STDOUT并返回。

if line == "EOF":
    self.lastcmd = ""
if line == "ctrl_c":  # You can handle the `KeyboardInterrupt` exception in this `if` branch.
    self.stdout.write("\n")
    return

您可以在下面看到完整的代码工作代码：

#! /usr/bin/python
# -*- coding: utf-8 -*-

from cmd import Cmd


class MyPrompt(Cmd):

    @staticmethod
    def do_exit(*args):
        return True

    def cmdloop(self, intro=None):
        """Repeatedly issue a prompt, accept input, parse an initial prefix
        off the received input, and dispatch to action methods, passing them
        the remainder of the line as argument.

        """

        self.preloop()
        if self.use_rawinput and self.completekey:
            try:
                import readline

                self.old_completer = readline.get_completer()
                readline.set_completer(self.complete)
                readline.parse_and_bind(self.completekey + ": complete")
            except ImportError:
                pass
        try:
            if intro is not None:
                self.intro = intro
            if self.intro:
                self.stdout.write(str(self.intro) + "\n")
            stop = None
            while not stop:
                if self.cmdqueue:
                    line = self.cmdqueue.pop(0)
                else:
                    if self.use_rawinput:
                        try:
                            line = input(self.prompt)
                        except EOFError:
                            line = "EOF"
                        except KeyboardInterrupt:
                            line = "ctrl_c"
                    else:
                        self.stdout.write(self.prompt)
                        self.stdout.flush()
                        line = self.stdin.readline()
                        if not len(line):
                            line = "EOF"
                        else:
                            line = line.rstrip("\r\n")
                line = self.precmd(line)
                stop = self.onecmd(line)
                stop = self.postcmd(stop, line)
            self.postloop()
        finally:
            if self.use_rawinput and self.completekey:
                try:
                    import readline

                    readline.set_completer(self.old_completer)
                except ImportError:
                    pass

    def onecmd(self, line):
        """Interpret the argument as though it had been typed in response
        to the prompt.

        This may be overridden, but should not normally need to be;
        see the precmd() and postcmd() methods for useful execution hooks.
        The return value is a flag indicating whether interpretation of
        commands by the interpreter should stop.

        """
        cmd, arg, line = self.parseline(line)
        if not line:
            return self.emptyline()
        if cmd is None:
            return self.default(line)
        self.lastcmd = line
        if line == "EOF":
            self.lastcmd = ""
        if line == "ctrl_c":
            self.stdout.write("\n")
            return
        if cmd == "":
            return self.default(line)
        else:
            try:
                func = getattr(self, "do_" + cmd)
            except AttributeError:
                return self.default(line)
            return func(arg)


p = MyPrompt()
p.cmdloop()

输出：

python3 test_cmd.py 
(Cmd) test
*** Unknown syntax: test
(Cmd) test1
*** Unknown syntax: test1
(Cmd) test2  <-- Ctrl+C has been pushed and I got a new empty prompt
(Cmd) test3  <-- Ctrl+C has been pushed and I got a new empty prompt
(Cmd)   <-- I got a new empty prompt

希望我的解决方案可以为您提供帮助。

Answer 2

您可以将键盘中断定义为例外：

try:
    your_code()
except KeyboardInterrupt:
    abort_code()

如何使用Python cmd shell捕获ctrl + c

2 个答案: