python - 在 ipython 中执行 `ls` 时如何修复 PermissionError？

Question

当我使用 python 2.7 (2.7.12) 运行 ipython(版本 5.4.1)并执行 ls 时，我得到一个 PermissionError :

$ ipython 
Python 2.7.12 (default, Dec  4 2017, 14:50:18) 
Type "copyright", "credits" or "license" for more information.

IPython 5.4.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: ls
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-1-e6d7425bc79f> in <module>()
----> 1 get_ipython().magic(u'ls ')

/home/adietz/.local/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in magic(self, arg_s)
   2158         magic_name, _, magic_arg_s = arg_s.partition(' ')
   2159         magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)
-> 2160         return self.run_line_magic(magic_name, magic_arg_s)
   2161 
   2162     #-------------------------------------------------------------------------

/home/adietz/.local/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in run_line_magic(self, magic_name, line)
   2079                 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
   2080             with self.builtin_trap:
-> 2081                 result = fn(*args,**kwargs)
   2082             return result
   2083 

/home/adietz/.local/lib/python2.7/site-packages/IPython/core/alias.pyc in __call__(self, rest)
    185             cmd = '%s %s' % (cmd % tuple(args[:nargs]),' '.join(args[nargs:]))
    186 
--> 187         self.shell.system(cmd)
    188 
    189 #-----------------------------------------------------------------------------

/home/adietz/.local/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in system_raw(self, cmd)
   2247             try:
   2248                 # Use env shell instead of default /bin/sh
-> 2249                 ec = subprocess.call(cmd, shell=True, executable=executable)
   2250             except KeyboardInterrupt:
   2251                 # intercept control-C; a long traceback is not useful here

/usr/lib/python2.7/subprocess.pyc in call(*popenargs, **kwargs)
    521     retcode = call(["ls", "-l"])
    522     """
--> 523     return Popen(*popenargs, **kwargs).wait()
    524 
    525 

/usr/lib/python2.7/subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
    709                                 p2cread, p2cwrite,
    710                                 c2pread, c2pwrite,
--> 711                                 errread, errwrite)
    712         except Exception:
    713             # Preserve original exception in case os.close raises.

/usr/lib/python2.7/subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, to_close, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
   1341                         raise
   1342                 child_exception = pickle.loads(data)
-> 1343                 raise child_exception
   1344 
   1345 

OSError: [Errno 13] Permission denied

我删除并重新安装了 ipython 但没有成功。

但是，当我执行 glob("*") 时，它按预期工作并且我获得了当前目录的内容。

有什么办法可以解决这个问题吗？或者如何找出原因？

附录

经过一些实验，我发现有问题的行是 subprocess.call 函数，我可以通过运行来重现错误

subprocess.call('ls', shell=True, executable=os.environ.get('SHELL', None))

此外，最后一部分的计算结果为空字符串:

In [7]: os.environ.get('SHELL', None)
Out[7]: ''

这似乎是令人反感的部分。没有它它运行良好

In [8]: subprocess.call('ls', shell=True)
adietz  Desktop  Documents  Downloads  examples.desktop  Music  opt  Pictures  Private  Projects  Public  Templates  Videos  Work
Out[8]: 0

Answer 1

由于某些未知原因，未定义在环境变量 SHELL 中指定的用户首选 shell 命令。通常定义它的地方是文件“/etc/passwd”(参见 here )。

因此手动设置此变量可以消除上述问题:

$ export SHELL=/bin/bash
$ ipython
Python 2.7.12 (default, Dec  4 2017, 14:50:18) 
Type "copyright", "credits" or "license" for more information.

IPython 5.4.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: ls
adietz@  Desktop/  Documents/  Downloads/  examples.desktop  Music/  opt/  Pictures/  Private/  Projects/  Public/  Templates/  Videos/  Work/