2 Wrappers around subprocess functionality that simulate an actual shell.
6 from wizard.shell import *
16 from wizard import util
18 wizard_bin = sys.argv[0]
20 This is the path to the wizard executable as specified
21 by the caller; it lets us recursively invoke wizard.
25 """Detects whether or not an argument list invokes a Python program."""
26 return args[0] == "python" or args[0] == "wizard"
28 def drop_priviledges(dir, log_file):
30 Checks if we are running as root. If we are, attempt to drop
31 priviledges to the user who owns ``dir``, by re-calling
32 itself using sudo with exec, such that the new process subsumes our
33 current one. If ``log_file`` is passed, the file is chown'ed
34 to the user we are dropping priviledges to, so the subprocess
39 uid = util.get_dir_uid(dir)
43 for k,v in os.environ.items():
44 if k.startswith('WIZARD_') or k == "SSH_GSSAPI_NAME":
45 args.append("%s=%s" % (k,v))
47 logging.debug("Dropping priviledges")
48 if log_file: os.chown(log_file, uid, -1)
49 os.execlp('sudo', 'sudo', '-u', '#' + str(uid), *args)
53 An advanced shell that performs logging. If ``dry`` is ``True``,
54 no commands are actually run.
56 def __init__(self, dry = False):
58 def call(self, *args, **kwargs):
60 Performs a system call. The actual executable and options should
61 be passed as arguments to this function. It will magically
62 ensure that 'wizard' as a command works. Several keyword arguments
65 :param python: explicitly marks the subprocess as Python or not Python
66 for improved error reporting. By default, we use
67 :func:`is_python` to autodetect this.
68 :param input: input to feed the subprocess on standard input.
69 :param interactive: whether or not directly hook up all pipes
70 to the controlling terminal, to allow interaction with subprocess.
71 :param strip: if ``True``, instead of returning a tuple,
72 return the string stdout output of the command with trailing newlines
73 removed. This emulates the behavior of backticks and ``$()`` in Bash.
74 Prefer to use :meth:`eval` instead (you should only need to explicitly
75 specify this if you are using another wrapper around this function).
76 :param log: if True, we log the call as INFO, if False, we log the call
77 as DEBUG, otherwise, we detect based on ``strip``.
80 :param stdin: a file-type object that will be written to or read from as a pipe.
81 :returns: a tuple of strings ``(stdout, stderr)``, or a string ``stdout``
82 if ``strip`` is specified.
85 >>> sh.call("echo", "Foobar")
87 >>> sh.call("cat", input='Foobar')
91 kwargs.setdefault("interactive", False)
92 kwargs.setdefault("strip", False)
93 kwargs.setdefault("python", None)
94 kwargs.setdefault("log", None)
95 kwargs.setdefault("stdout", subprocess.PIPE)
96 kwargs.setdefault("stdin", subprocess.PIPE)
97 kwargs.setdefault("stderr", subprocess.PIPE)
98 msg = "Running `" + ' '.join(args) + "`"
99 if kwargs["strip"] and not kwargs["log"] is True or kwargs["log"] is False:
107 if kwargs["python"] is None and is_python(args):
108 kwargs["python"] = True
109 if args[0] == "wizard":
112 kwargs.setdefault("input", None)
113 if kwargs["interactive"]:
118 stdout=kwargs["stdout"]
119 stdin=kwargs["stdin"]
120 stderr=kwargs["stderr"]
121 # XXX: There is a possible problem here where we can fill up
122 # the kernel buffer if we have 64KB of data. This shouldn't
123 # be a problem, and the fix for such case would be to write to
124 # temporary files instead of a pipe.
125 # Another possible way of fixing this is converting from a
126 # waitpid() pump to a select() pump, creating a pipe to
127 # ourself, and then setting up a
128 # SIGCHILD handler to write a single byte to the pipe to get
129 # us out of select() when a subprocess exits.
130 proc = subprocess.Popen(args, stdout=stdout, stderr=stderr, stdin=stdin)
131 if self._async(proc, args, **kwargs):
133 stdout, stderr = proc.communicate(kwargs["input"])
134 if not kwargs["interactive"]:
136 self._log(None, stderr)
138 self._log(stdout, stderr)
140 if kwargs["python"]: eclass = PythonCallError
141 else: eclass = CallError
142 raise eclass(proc.returncode, args, stdout, stderr)
144 return str(stdout).rstrip("\n")
145 return (stdout, stderr)
146 def _log(self, stdout, stderr):
147 """Logs the standard output and standard input from a command."""
149 logging.debug("STDOUT:\n" + stdout)
151 logging.debug("STDERR:\n" + stderr)
154 def _async(self, *args, **kwargs):
156 def callAsUser(self, *args, **kwargs):
158 Performs a system call as a different user. This is only possible
159 if you are running as root. Keyword arguments
160 are the same as :meth:`call` with the following additions:
162 :param user: name of the user to run command as.
163 :param uid: uid of the user to run command as.
167 The resulting system call internally uses :command:`sudo`,
168 and as such environment variables will get scrubbed. We
169 manually preserve :envvar:`SSH_GSSAPI_NAME`.
171 user = kwargs.pop("user", None)
172 uid = kwargs.pop("uid", None)
173 kwargs.setdefault("python", is_python(args))
174 if not user and not uid: return self.call(*args, **kwargs)
175 if os.getenv("SSH_GSSAPI_NAME"):
176 # This might be generalized as "preserve some environment"
178 args.insert(0, "SSH_GSSAPI_NAME=" + os.getenv("SSH_GSSAPI_NAME"))
179 if uid: return self.call("sudo", "-u", "#" + str(uid), *args, **kwargs)
180 if user: return self.call("sudo", "-u", user, *args, **kwargs)
181 def safeCall(self, *args, **kwargs):
183 Checks if the owner of the current working directory is the same
184 as the current user, and if it isn't, attempts to sudo to be
185 that user. The intended use case is for calling Git commands
186 when running as root, but this method should be used when
187 interfacing with any moderately complex program that depends
188 on working directory context. Keyword arguments are the
189 same as :meth:`call`.
191 uid = os.stat(os.getcwd()).st_uid
192 # consider also checking ruid?
193 if uid != os.geteuid():
195 return self.callAsUser(*args, **kwargs)
197 return self.call(*args, **kwargs)
198 def eval(self, *args, **kwargs):
200 Evaluates a command and returns its output, with trailing newlines
201 stripped (like backticks in Bash). This is a convenience method for
202 calling :meth:`call` with ``strip``.
205 >>> sh.eval("echo", "Foobar")
208 kwargs["strip"] = True
209 return self.call(*args, **kwargs)
211 class ParallelShell(Shell):
213 Modifies the semantics of :class:`Shell` so that
214 commands are queued here, and executed in parallel using waitpid
215 with ``max`` subprocesses, and result in callback execution
218 .. method:: call(*args, **kwargs)
220 Enqueues a system call for parallel processing. If there are
221 no openings in the queue, this will block. Keyword arguments
222 are the same as :meth:`Shell.call` with the following additions:
224 :param on_success: Callback function for success (zero exit status).
225 The callback function should accept two arguments,
226 ``stdout`` and ``stderr``.
227 :param on_error: Callback function for failure (nonzero exit status).
228 The callback function should accept one argument, the
229 exception that would have been thrown by the synchronous
231 :return: The :class:`subprocess.Proc` object that was opened.
233 .. method:: callAsUser(*args, **kwargs)
235 Enqueues a system call under a different user for parallel
236 processing. Keyword arguments are the same as
237 :meth:`Shell.callAsUser` with the additions of keyword
238 arguments from :meth:`call`.
240 .. method:: safeCall(*args, **kwargs)
242 Enqueues a "safe" call for parallel processing. Keyword
243 arguments are the same as :meth:`Shell.safeCall` with the
244 additions of keyword arguments from :meth:`call`.
246 .. method:: eval(*args, **kwargs)
248 No difference from :meth:`call`. Consider having a
249 non-parallel shell if the program you are shelling out
253 def __init__(self, dry = False, max = 10):
254 super(ParallelShell, self).__init__(dry=dry)
256 self.max = max # maximum of commands to run in parallel
258 def make(no_parallelize, max):
259 """Convenience method oriented towards command modules."""
261 return DummyParallelShell()
263 return ParallelShell(max=max)
264 def _async(self, proc, args, python, on_success, on_error, **kwargs):
266 Gets handed a :class:`subprocess.Proc` object from our deferred
267 execution. See :meth:`Shell.call` source code for details.
269 self.running[proc.pid] = (proc, args, python, on_success, on_error)
270 return True # so that the parent function returns
273 Blocking call that waits for an open subprocess slot. This is
274 automatically called by :meth:`Shell.call`.
276 # XXX: This API sucks; the actuall call/callAsUser call should
277 # probably block automatically (unless I have a good reason not to)
278 # bail out immediately on initial ramp up
279 if len(self.running) < self.max: return
280 # now, wait for open pids.
282 self.reap(*os.waitpid(-1, 0))
284 if e.errno == errno.ECHILD: return
287 """Waits for all of our subprocesses to terminate."""
290 self.reap(*os.waitpid(-1, 0))
292 if e.errno == errno.ECHILD: return
294 def reap(self, pid, status):
295 """Reaps a process."""
296 # ooh, zombie process. reap it
297 proc, args, python, on_success, on_error = self.running.pop(pid)
298 # XXX: this is slightly dangerous; should actually use
300 stdout = proc.stdout.read()
301 stderr = proc.stderr.read()
302 self._log(stdout, stderr)
304 if python: eclass = PythonCallError
305 else: eclass = CallError
306 on_error(eclass(proc.returncode, args, stdout, stderr))
308 on_success(stdout, stderr)
311 class DummyParallelShell(ParallelShell):
312 """Same API as :class:`ParallelShell`, but doesn't actually
313 parallelize (i.e. all calls to :meth:`wait` block.)"""
314 def __init__(self, dry = False):
315 super(DummyParallelShell, self).__init__(dry=dry, max=1)
317 class Error(wizard.Error):
318 """Base exception for this module"""
321 class CallError(Error):
322 """Indicates that a subprocess call returned a nonzero exit status."""
323 #: The exit code of the failed subprocess.
325 #: List of the program and arguments that failed.
327 #: The stdout of the program.
329 #: The stderr of the program.
331 def __init__(self, code, args, stdout, stderr):
337 compact = self.stderr.rstrip().split("\n")[-1]
338 return "%s (exited with %d)\n%s" % (compact, self.code, self.stderr)
340 class PythonCallError(CallError):
342 Indicates that a Python subprocess call had an uncaught exception.
343 This exception also contains the attributes of :class:`CallError`.
345 #: Name of the uncaught exception.
347 def __init__(self, code, args, stdout, stderr):
348 if stderr: self.name = util.get_exception_name(stderr)
349 CallError.__init__(self, code, args, stdout, stderr)
352 return "PythonCallError [%s]\n%s" % (self.name, self.stderr)
354 return "PythonCallError\n%s" % self.stderr