# subprocess - Subprocesses with accessible I/O streams # # For more information about this module, see PEP 324. # # Copyright (c) 2003-2005 by Peter Astrand # # Licensed to PSF under a Contributor Agreement. # See http://www.python.org/2.4/license for licensing details. r"""subprocess - Subprocesses with accessible I/O streams This module allows you to spawn processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several other, older modules and functions, like: os.system os.spawn* Information about how the subprocess module can be used to replace these modules and functions can be found below. Using the subprocess module =========================== This module defines one class called Popen: class Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=False, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False): Arguments are: args should be a string, or a sequence of program arguments. The program to execute is normally the first item in the args sequence or string, but can be explicitly set by using the executable argument. On UNIX, with shell=False (default): In this case, the Popen class uses os.execvp() to execute the child program. args should normally be a sequence. A string will be treated as a sequence with the string as the only item (the program to execute). On UNIX, with shell=True: If args is a string, it specifies the command string to execute through the shell. If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional shell arguments. On Windows: the Popen class uses CreateProcess() to execute the child program, which operates on strings. If args is a sequence, it will be converted to a string using the list2cmdline method. Please note that not all MS Windows applications interpret the command line the same way: The list2cmdline is designed for applications using the same rules as the MS C runtime. bufsize, if given, has the same meaning as the corresponding argument to the built-in open() function: 0 means unbuffered, 1 means line buffered, any other positive value means use a buffer of (approximately) that size. A negative bufsize means to use the system default, which usually means fully buffered. The default value for bufsize is 0 (unbuffered). stdin, stdout and stderr specify the executed programs' standard input, standard output and standard error file handles, respectively. Valid values are PIPE, an existing file descriptor (a positive integer), an existing file object, and None. PIPE indicates that a new pipe to the child should be created. With None, no redirection will occur; the child's file handles will be inherited from the parent. Additionally, stderr can be STDOUT, which indicates that the stderr data from the applications should be captured into the same file handle as for stdout. On UNIX, if preexec_fn is set to a callable object, this object will be called in the child process just before the child is executed. The use of preexec_fn is not thread safe, using it in the presence of threads could lead to a deadlock in the child process before the new executable is executed. If close_fds is true, all file descriptors except 0, 1 and 2 will be closed before the child process is executed. if shell is true, the specified command will be executed through the shell. If cwd is not None, the current directory will be changed to cwd before the child is executed. On UNIX, if restore_signals is True all signals that Python sets to SIG_IGN are restored to SIG_DFL in the child process before the exec. Currently this includes the SIGPIPE, SIGXFZ and SIGXFSZ signals. This parameter does nothing on Windows. On UNIX, if start_new_session is True, the setsid() system call will be made in the child process prior to executing the command. If env is not None, it defines the environment variables for the new process. If universal_newlines is true, the file objects stdout and stderr are opened as a text files, but lines may be terminated by any of '\n', the Unix end-of-line convention, '\r', the Macintosh convention or '\r\n', the Windows convention. All of these external representations are seen as '\n' by the Python program. Note: This feature is only available if Python is built with universal newline support (the default). Also, the newlines attribute of the file objects stdout, stdin and stderr are not updated by the communicate() method. The startupinfo and creationflags, if given, will be passed to the underlying CreateProcess() function. They can specify things such as appearance of the main window and priority for the new process. (Windows only) This module also defines some shortcut functions: call(*popenargs, **kwargs): Run command with arguments. Wait for command to complete, then return the returncode attribute. The arguments are the same as for the Popen constructor. Example: >>> retcode = subprocess.call(["ls", "-l"]) check_call(*popenargs, **kwargs): Run command with arguments. Wait for command to complete. If the exit code was zero then return, otherwise raise CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute. The arguments are the same as for the Popen constructor. Example: >>> subprocess.check_call(["ls", "-l"]) 0 getstatusoutput(cmd): Return (status, output) of executing cmd in a shell. Execute the string 'cmd' in a shell with os.popen() and return a 2-tuple (status, output). cmd is actually run as '{ cmd ; } 2>&1', so that the returned output will contain output or error messages. A trailing newline is stripped from the output. The exit status for the command can be interpreted according to the rules for the C function wait(). Example: >>> subprocess.getstatusoutput('ls /bin/ls') (0, '/bin/ls') >>> subprocess.getstatusoutput('cat /bin/junk') (256, 'cat: /bin/junk: No such file or directory') >>> subprocess.getstatusoutput('/bin/junk') (256, 'sh: /bin/junk: not found') getoutput(cmd): Return output (stdout or stderr) of executing cmd in a shell. Like getstatusoutput(), except the exit status is ignored and the return value is a string containing the command's output. Example: >>> subprocess.getoutput('ls /bin/ls') '/bin/ls' check_output(*popenargs, **kwargs): Run command with arguments and return its output as a byte string. If the exit code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and output in the output attribute. The arguments are the same as for the Popen constructor. Example: >>> output = subprocess.check_output(["ls", "-l", "/dev/null"]) Exceptions ---------- Exceptions raised in the child process, before the new program has started to execute, will be re-raised in the parent. Additionally, the exception object will have one extra attribute called 'child_traceback', which is a string containing traceback information from the childs point of view. The most common exception raised is OSError. This occurs, for example, when trying to execute a non-existent file. Applications should prepare for OSErrors. A ValueError will be raised if Popen is called with invalid arguments. check_call() and check_output() will raise CalledProcessError, if the called process returns a non-zero return code. Security -------- Unlike some other popen functions, this implementation will never call /bin/sh implicitly. This means that all characters, including shell metacharacters, can safely be passed to child processes. Popen objects ============= Instances of the Popen class have the following methods: poll() Check if child process has terminated. Returns returncode attribute. wait() Wait for child process to terminate. Returns returncode attribute. communicate(input=None) Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child. communicate() returns a tuple (stdout, stderr). Note: The data read is buffered in memory, so do not use this method if the data size is large or unlimited. The following attributes are also available: stdin If the stdin argument is PIPE, this attribute is a file object that provides input to the child process. Otherwise, it is None. stdout If the stdout argument is PIPE, this attribute is a file object that provides output from the child process. Otherwise, it is None. stderr If the stderr argument is PIPE, this attribute is file object that provides error output from the child process. Otherwise, it is None. pid The process ID of the child process. returncode The child return code. A None value indicates that the process hasn't terminated yet. A negative value -N indicates that the child was terminated by signal N (UNIX only). Replacing older functions with the subprocess module ==================================================== In this section, "a ==> b" means that b can be used as a replacement for a. Note: All functions in this section fail (more or less) silently if the executed program cannot be found; this module raises an OSError exception. In the following examples, we assume that the subprocess module is imported with "from subprocess import *". Replacing /bin/sh shell backquote --------------------------------- output=`mycmd myarg` ==> output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0] Replacing shell pipe line ------------------------- output=`dmesg | grep hda` ==> p1 = Popen(["dmesg"], stdout=PIPE) p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE) output = p2.communicate()[0] Replacing os.system() --------------------- sts = os.system("mycmd" + " myarg") ==> p = Popen("mycmd" + " myarg", shell=True) pid, sts = os.waitpid(p.pid, 0) Note: * Calling the program through the shell is usually not required. * It's easier to look at the returncode attribute than the exitstatus. A more real-world example would look like this: try: retcode = call("mycmd" + " myarg", shell=True) if retcode < 0: print("Child was terminated by signal", -retcode, file=sys.stderr) else: print("Child returned", retcode, file=sys.stderr) except OSError as e: print("Execution failed:", e, file=sys.stderr) Replacing os.spawn* ------------------- P_NOWAIT example: pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg") ==> pid = Popen(["/bin/mycmd", "myarg"]).pid P_WAIT example: retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg") ==> retcode = call(["/bin/mycmd", "myarg"]) Vector example: os.spawnvp(os.P_NOWAIT, path, args) ==> Popen([path] + args[1:]) Environment example: os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env) ==> Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"}) """ import sys mswindows = (sys.platform == "win32") import io import os import traceback import gc import signal import builtins import warnings # Exception classes used by this module. class CalledProcessError(Exception): """This exception is raised when a process run by check_call() or check_output() returns a non-zero exit status. The exit status will be stored in the returncode attribute; check_output() will also store the output in the output attribute. """ def __init__(self, returncode, cmd, output=None): self.returncode = returncode self.cmd = cmd self.output = output def __str__(self): return "Command '%s' returned non-zero exit status %d" % (self.cmd, self.returncode) if mswindows: import threading import msvcrt import _subprocess class STARTUPINFO: dwFlags = 0 hStdInput = None hStdOutput = None hStdError = None wShowWindow = 0 class pywintypes: error = IOError else: import select _has_poll = hasattr(select, 'poll') import errno import fcntl import pickle try: import _posixsubprocess except ImportError: _posixsubprocess = None warnings.warn("The _posixsubprocess module is not being used. " "Child process reliability may suffer if your " "program uses threads.", RuntimeWarning) # When select or poll has indicated that the file is writable, # we can write up to _PIPE_BUF bytes without risk of blocking. # POSIX defines PIPE_BUF as >= 512. _PIPE_BUF = getattr(select, 'PIPE_BUF', 512) __all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput", "getoutput", "check_output", "CalledProcessError"] if mswindows: from _subprocess import CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP __all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP"]) try: MAXFD = os.sysconf("SC_OPEN_MAX") except: MAXFD = 256 _active = [] def _cleanup(): for inst in _active[:]: res = inst._internal_poll(_deadstate=sys.maxsize) if res is not None and res >= 0: try: _active.remove(inst) except ValueError: # This can happen if two threads create a new Popen instance. # It's harmless that it was already removed, so ignore. pass PIPE = -1 STDOUT = -2 def _eintr_retry_call(func, *args): while True: try: return func(*args) except OSError as e: if e.errno == errno.EINTR: continue raise def call(*popenargs, **kwargs): """Run command with arguments. Wait for command to complete, then return the returncode attribute. The arguments are the same as for the Popen constructor. Example: retcode = call(["ls", "-l"]) """ return Popen(*popenargs, **kwargs).wait() def check_call(*popenargs, **kwargs): """Run command with arguments. Wait for command to complete. If the exit code was zero then return, otherwise raise CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute. The arguments are the same as for the Popen constructor. Example: check_call(["ls", "-l"]) """ retcode = call(*popenargs, **kwargs) if retcode: cmd = kwargs.get("args") if cmd is None: cmd = popenargs[0] raise CalledProcessError(retcode, cmd) return 0 def check_output(*popenargs, **kwargs): r"""Run command with arguments and return its output as a byte string. If the exit code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and output in the output attribute. The arguments are the same as for the Popen constructor. Example: >>> check_output(["ls", "-l", "/dev/null"]) b'crw-rw-rw- 1 root root 1, 3 Oct 18 2007 /dev/null\n' The stdout argument is not allowed as it is used internally. To capture standard error in the result, use stderr=STDOUT. >>> check_output(["/bin/sh", "-c", ... "ls -l non_existent_file ; exit 0"], ... stderr=STDOUT) b'ls: non_existent_file: No such file or directory\n' """ if 'stdout' in kwargs: raise ValueError('stdout argument not allowed, it will be overridden.') process = Popen(*popenargs, stdout=PIPE, **kwargs) output, unused_err = process.communicate() retcode = process.poll() if retcode: cmd = kwargs.get("args") if cmd is None: cmd = popenargs[0] raise CalledProcessError(retcode, cmd, output=output) return output def list2cmdline(seq): """ Translate a sequence of arguments into a command line string, using the same rules as the MS C runtime: 1) Arguments are delimited by white space, which is either a space or a tab. 2) A string surrounded by double quotation marks is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument. 3) A double quotation mark preceded by a backslash is interpreted as a literal double quotation mark. 4) Backslashes are interpreted literally, unless they immediately precede a double quotation mark. 5) If backslashes immediately precede a double quotation mark, every pair of backslashes is interpreted as a literal backslash. If the number of backslashes is odd, the last backslash escapes the next double quotation mark as described in rule 3. """ # See # http://msdn.microsoft.com/en-us/library/17w5ykft.aspx # or search http://msdn.microsoft.com for # "Parsing C++ Command-Line Arguments" result = [] needquote = False for arg in seq: bs_buf = [] # Add a space to separate this argument from the others if result: result.append(' ') needquote = (" " in arg) or ("\t" in arg) or not arg if needquote: result.append('"') for c in arg: if c == '\\': # Don't know if we need to double yet. bs_buf.append(c) elif c == '"': # Double backslashes. result.append('\\' * len(bs_buf)*2) bs_buf = [] result.append('\\"') else: # Normal char if bs_buf: result.extend(bs_buf) bs_buf = [] result.append(c) # Add remaining backslashes, if any. if bs_buf: result.extend(bs_buf) if needquote: result.extend(bs_buf) result.append('"') return ''.join(result) # Various tools for executing commands and looking at their output and status. # # NB This only works (and is only relevant) for UNIX. def getstatusoutput(cmd): """Return (status, output) of executing cmd in a shell. Execute the string 'cmd' in a shell with os.popen() and return a 2-tuple (status, output). cmd is actually run as '{ cmd ; } 2>&1', so that the returned output will contain output or error messages. A trailing newline is stripped from the output. The exit status for the command can be interpreted according to the rules for the C function wait(). Example: >>> import subprocess >>> subprocess.getstatusoutput('ls /bin/ls') (0, '/bin/ls') >>> subprocess.getstatusoutput('cat /bin/junk') (256, 'cat: /bin/junk: No such file or directory') >>> subprocess.getstatusoutput('/bin/junk') (256, 'sh: /bin/junk: not found') """ pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r') text = pipe.read() sts = pipe.close() if sts is None: sts = 0 if text[-1:] == '\n': text = text[:-1] return sts, text def getoutput(cmd): """Return output (stdout or stderr) of executing cmd in a shell. Like getstatusoutput(), except the exit status is ignored and the return value is a string containing the command's output. Example: >>> import subprocess >>> subprocess.getoutput('ls /bin/ls') '/bin/ls' """ return getstatusoutput(cmd)[1] class Popen(object): def __init__(self, args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=None, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False, pass_fds=()): """Create new Popen instance.""" _cleanup() self._child_created = False if bufsize is None: bufsize = 0 # Restore default if not isinstance(bufsize, int): raise TypeError("bufsize must be an integer") if close_fds is None: # Notification for http://bugs.python.org/issue7213 & issue2320 warnings.warn( 'The close_fds parameter was not specified. Its default' ' behavior will change in a future Python version. ' ' Most users should set it to True. Please' ' update your code explicitly set close_fds.', DeprecationWarning) if mswindows: if preexec_fn is not None: raise ValueError("preexec_fn is not supported on Windows " "platforms") if close_fds and (stdin is not None or stdout is not None or stderr is not None): raise ValueError("close_fds is not supported on Windows " "platforms if you redirect stdin/stdout/stderr") else: # POSIX if startupinfo is not None: raise ValueError("startupinfo is only supported on Windows " "platforms") if creationflags != 0: raise ValueError("creationflags is only supported on Windows " "platforms") if pass_fds and not close_fds: raise ValueError("pass_fds requires close_fds=True.") self.stdin = None self.stdout = None self.stderr = None self.pid = None self.returncode = None self.universal_newlines = universal_newlines # Input and output objects. The general principle is like # this: # # Parent Child # ------ ----- # p2cwrite ---stdin---> p2cread # c2pread <--stdout--- c2pwrite # errread <--stderr--- errwrite # # On POSIX, the child objects are file descriptors. On # Windows, these are Windows file handles. The parent objects # are file descriptors on both platforms. The parent objects # are -1 when not using PIPEs. The child objects are -1 # when not redirecting. (p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite) = self._get_handles(stdin, stdout, stderr) self._execute_child(args, executable, preexec_fn, close_fds, pass_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, restore_signals, start_new_session) if mswindows: if p2cwrite != -1: p2cwrite = msvcrt.open_osfhandle(p2cwrite.Detach(), 0) if c2pread != -1: c2pread = msvcrt.open_osfhandle(c2pread.Detach(), 0) if errread != -1: errread = msvcrt.open_osfhandle(errread.Detach(), 0) if bufsize == 0: bufsize = 1 # Nearly unbuffered (XXX for now) if p2cwrite != -1: self.stdin = io.open(p2cwrite, 'wb', bufsize) if self.universal_newlines: self.stdin = io.TextIOWrapper(self.stdin) if c2pread != -1: self.stdout = io.open(c2pread, 'rb', bufsize) if universal_newlines: self.stdout = io.TextIOWrapper(self.stdout) if errread != -1: self.stderr = io.open(errread, 'rb', bufsize) if universal_newlines: self.stderr = io.TextIOWrapper(self.stderr) def _translate_newlines(self, data, encoding): data = data.replace(b"\r\n", b"\n").replace(b"\r", b"\n") return data.decode(encoding) def __enter__(self): return self def __exit__(self, type, value, traceback): if self.stdout: self.stdout.close() if self.stderr: self.stderr.close() if self.stdin: self.stdin.close() def __del__(self, _maxsize=sys.maxsize, _active=_active): if not self._child_created: # We didn't get to successfully create a child process. return # In case the child hasn't been waited on, check if it's done. self._internal_poll(_deadstate=_maxsize) if self.returncode is None and _active is not None: # Child is still running, keep us alive until we can wait on it. _active.append(self) def communicate(self, input=None): """Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child. communicate() returns a tuple (stdout, stderr).""" # Optimization: If we are only using one pipe, or no pipe at # all, using select() or threads is unnecessary. if [self.stdin, self.stdout, self.stderr].count(None) >= 2: stdout = None stderr = None if self.stdin: if input: self.stdin.write(input) self.stdin.close() elif self.stdout: stdout = self.stdout.read() self.stdout.close() elif self.stderr: stderr = self.stderr.read() self.stderr.close() self.wait() return (stdout, stderr) return self._communicate(input) def poll(self): return self._internal_poll() if mswindows: # # Windows methods # def _get_handles(self, stdin, stdout, stderr): """Construct and return tuple with IO objects: p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite """ if stdin is None and stdout is None and stderr is None: return (-1, -1, -1, -1, -1, -1) p2cread, p2cwrite = -1, -1 c2pread, c2pwrite = -1, -1 errread, errwrite = -1, -1 if stdin is None: p2cread = _subprocess.GetStdHandle(_subprocess.STD_INPUT_HANDLE) if p2cread is None: p2cread, _ = _subprocess.CreatePipe(None, 0) elif stdin == PIPE: p2cread, p2cwrite = _subprocess.CreatePipe(None, 0) elif isinstance(stdin, int): p2cread = msvcrt.get_osfhandle(stdin) else: # Assuming file-like object p2cread = msvcrt.get_osfhandle(stdin.fileno()) p2cread = self._make_inheritable(p2cread) if stdout is None: c2pwrite = _subprocess.GetStdHandle(_subprocess.STD_OUTPUT_HANDLE) if c2pwrite is None: _, c2pwrite = _subprocess.CreatePipe(None, 0) elif stdout == PIPE: c2pread, c2pwrite = _subprocess.CreatePipe(None, 0) elif isinstance(stdout, int): c2pwrite = msvcrt.get_osfhandle(stdout) else: # Assuming file-like object c2pwrite = msvcrt.get_osfhandle(stdout.fileno()) c2pwrite = self._make_inheritable(c2pwrite) if stderr is None: errwrite = _subprocess.GetStdHandle(_subprocess.STD_ERROR_HANDLE) if errwrite is None: _, errwrite = _subprocess.CreatePipe(None, 0) elif stderr == PIPE: errread, errwrite = _subprocess.CreatePipe(None, 0) elif stderr == STDOUT: errwrite = c2pwrite elif isinstance(stderr, int): errwrite = msvcrt.get_osfhandle(stderr) else: # Assuming file-like object errwrite = msvcrt.get_osfhandle(stderr.fileno()) errwrite = self._make_inheritable(errwrite) return (p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite) def _make_inheritable(self, handle): """Return a duplicate of handle, which is inheritable""" return _subprocess.DuplicateHandle(_subprocess.GetCurrentProcess(), handle, _subprocess.GetCurrentProcess(), 0, 1, _subprocess.DUPLICATE_SAME_ACCESS) def _find_w9xpopen(self): """Find and return absolut path to w9xpopen.exe""" w9xpopen = os.path.join( os.path.dirname(_subprocess.GetModuleFileName(0)), "w9xpopen.exe") if not os.path.exists(w9xpopen): # Eeek - file-not-found - possibly an embedding # situation - see if we can locate it in sys.exec_prefix w9xpopen = os.path.join(os.path.dirname(sys.exec_prefix), "w9xpopen.exe") if not os.path.exists(w9xpopen): raise RuntimeError("Cannot locate w9xpopen.exe, which is " "needed for Popen to work with your " "shell or platform.") return w9xpopen def _execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, unused_restore_signals, unused_start_new_session): """Execute program (MS Windows version)""" assert not pass_fds, "pass_fds not yet supported on Windows" if not isinstance(args, str): args = list2cmdline(args) # Process startup details if startupinfo is None: startupinfo = STARTUPINFO() if -1 not in (p2cread, c2pwrite, errwrite): startupinfo.dwFlags |= _subprocess.STARTF_USESTDHANDLES startupinfo.hStdInput = p2cread startupinfo.hStdOutput = c2pwrite startupinfo.hStdError = errwrite if shell: startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW startupinfo.wShowWindow = _subprocess.SW_HIDE comspec = os.environ.get("COMSPEC", "cmd.exe") args = '{} /c "{}"'.format (comspec, args) if (_subprocess.GetVersion() >= 0x80000000 or os.path.basename(comspec).lower() == "command.com"): # Win9x, or using command.com on NT. We need to # use the w9xpopen intermediate program. For more # information, see KB Q150956 # (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp) w9xpopen = self._find_w9xpopen() args = '"%s" %s' % (w9xpopen, args) # Not passing CREATE_NEW_CONSOLE has been known to # cause random failures on win9x. Specifically a # dialog: "Your program accessed mem currently in # use at xxx" and a hopeful warning about the # stability of your system. Cost is Ctrl+C won't # kill children. creationflags |= _subprocess.CREATE_NEW_CONSOLE # Start the process try: hp, ht, pid, tid = _subprocess.CreateProcess(executable, args, # no special security None, None, int(not close_fds), creationflags, env, cwd, startupinfo) except pywintypes.error as e: # Translate pywintypes.error to WindowsError, which is # a subclass of OSError. FIXME: We should really # translate errno using _sys_errlist (or simliar), but # how can this be done from Python? raise WindowsError(*e.args) finally: # Child is launched. Close the parent's copy of those pipe # handles that only the child should have open. You need # to make sure that no handles to the write end of the # output pipe are maintained in this process or else the # pipe will not close when the child process exits and the # ReadFile will hang. if p2cread != -1: p2cread.Close() if c2pwrite != -1: c2pwrite.Close() if errwrite != -1: errwrite.Close() # Retain the process handle, but close the thread handle self._child_created = True self._handle = hp self.pid = pid ht.Close() def _internal_poll(self, _deadstate=None, _WaitForSingleObject=_subprocess.WaitForSingleObject, _WAIT_OBJECT_0=_subprocess.WAIT_OBJECT_0, _GetExitCodeProcess=_subprocess.GetExitCodeProcess): """Check if child process has terminated. Returns returncode attribute. This method is called by __del__, so it can only refer to objects in its local scope. """ if self.returncode is None: if _WaitForSingleObject(self._handle, 0) == _WAIT_OBJECT_0: self.returncode = _GetExitCodeProcess(self._handle) return self.returncode def wait(self): """Wait for child process to terminate. Returns returncode attribute.""" if self.returncode is None: _subprocess.WaitForSingleObject(self._handle, _subprocess.INFINITE) self.returncode = _subprocess.GetExitCodeProcess(self._handle) return self.returncode def _readerthread(self, fh, buffer): buffer.append(fh.read()) def _communicate(self, input): stdout = None # Return stderr = None # Return if self.stdout: stdout = [] stdout_thread = threading.Thread(target=self._readerthread, args=(self.stdout, stdout)) stdout_thread.daemon = True stdout_thread.start() if self.stderr: stderr = [] stderr_thread = threading.Thread(target=self._readerthread, args=(self.stderr, stderr)) stderr_thread.daemon = True stderr_thread.start() if self.stdin: if input is not None: self.stdin.write(input) self.stdin.close() if self.stdout: stdout_thread.join() if self.stderr: stderr_thread.join() # All data exchanged. Translate lists into strings. if stdout is not None: stdout = stdout[0] if stderr is not None: stderr = stderr[0] self.wait() return (stdout, stderr) def send_signal(self, sig): """Send a signal to the process """ if sig == signal.SIGTERM: self.terminate() elif sig == signal.CTRL_C_EVENT: os.kill(self.pid, signal.CTRL_C_EVENT) elif sig == signal.CTRL_BREAK_EVENT: os.kill(self.pid, signal.CTRL_BREAK_EVENT) else: raise ValueError("Unsupported signal: {}".format(sig)) def terminate(self): """Terminates the process """ _subprocess.TerminateProcess(self._handle, 1) kill = terminate else: # # POSIX methods # def _get_handles(self, stdin, stdout, stderr): """Construct and return tuple with IO objects: p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite """ p2cread, p2cwrite = -1, -1 c2pread, c2pwrite = -1, -1 errread, errwrite = -1, -1 if stdin is None: pass elif stdin == PIPE: p2cread, p2cwrite = os.pipe() elif isinstance(stdin, int): p2cread = stdin else: # Assuming file-like object p2cread = stdin.fileno() if stdout is None: pass elif stdout == PIPE: c2pread, c2pwrite = os.pipe() elif isinstance(stdout, int): c2pwrite = stdout else: # Assuming file-like object c2pwrite = stdout.fileno() if stderr is None: pass elif stderr == PIPE: errread, errwrite = os.pipe() elif stderr == STDOUT: errwrite = c2pwrite elif isinstance(stderr, int): errwrite = stderr else: # Assuming file-like object errwrite = stderr.fileno() return (p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite) def _set_cloexec_flag(self, fd): try: cloexec_flag = fcntl.FD_CLOEXEC except AttributeError: cloexec_flag = 1 old = fcntl.fcntl(fd, fcntl.F_GETFD) fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag) def _close_fds(self, but): os.closerange(3, but) os.closerange(but + 1, MAXFD) def _close_all_but_a_sorted_few_fds(self, fds_to_keep): # precondition: fds_to_keep must be sorted and unique start_fd = 3 for fd in fds_to_keep: if fd > start_fd: os.closerange(start_fd, fd) start_fd = fd + 1 if start_fd <= MAXFD: os.closerange(start_fd, MAXFD) def _execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, restore_signals, start_new_session): """Execute program (POSIX version)""" if isinstance(args, str): args = [args] else: args = list(args) if shell: args = ["/bin/sh", "-c"] + args if executable: args[0] = executable if executable is None: executable = args[0] # For transferring possible exec failure from child to parent. # Data format: "exception name:hex errno:description" # Pickle is not used; it is complex and involves memory allocation. errpipe_read, errpipe_write = os.pipe() try: try: self._set_cloexec_flag(errpipe_write) if _posixsubprocess: # We must avoid complex work that could involve # malloc or free in the child process to avoid # potential deadlocks, thus we do all this here. # and pass it to fork_exec() if env: env_list = [os.fsencode(k) + b'=' + os.fsencode(v) for k, v in env.items()] else: env_list = None # Use execv instead of execve. executable = os.fsencode(executable) if os.path.dirname(executable): executable_list = (executable,) else: # This matches the behavior of os._execvpe(). executable_list = tuple( os.path.join(os.fsencode(dir), executable) for dir in os.get_exec_path(env)) fds_to_keep = set(pass_fds) fds_to_keep.add(errpipe_write) self.pid = _posixsubprocess.fork_exec( args, executable_list, close_fds, sorted(fds_to_keep), cwd, env_list, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, errpipe_read, errpipe_write, restore_signals, start_new_session, preexec_fn) else: # Pure Python implementation: It is not thread safe. # This implementation may deadlock in the child if your # parent process has any other threads running. gc_was_enabled = gc.isenabled() # Disable gc to avoid bug where gc -> file_dealloc -> # write to stderr -> hang. See issue1336 gc.disable() try: self.pid = os.fork() except: if gc_was_enabled: gc.enable() raise self._child_created = True if self.pid == 0: # Child try: # Close parent's pipe ends if p2cwrite != -1: os.close(p2cwrite) if c2pread != -1: os.close(c2pread) if errread != -1: os.close(errread) os.close(errpipe_read) # Dup fds for child if p2cread != -1: os.dup2(p2cread, 0) if c2pwrite != -1: os.dup2(c2pwrite, 1) if errwrite != -1: os.dup2(errwrite, 2) # Close pipe fds. Make sure we don't close the # same fd more than once, or standard fds. if p2cread != -1 and p2cread not in (0,): os.close(p2cread) if (c2pwrite != -1 and c2pwrite not in (p2cread, 1)): os.close(c2pwrite) if (errwrite != -1 and errwrite not in (p2cread, c2pwrite, 2)): os.close(errwrite) # Close all other fds, if asked for if close_fds: if pass_fds: fds_to_keep = set(pass_fds) fds_to_keep.add(errpipe_write) self._close_all_but_a_sorted_few_fds( sorted(fds_to_keep)) else: self._close_fds(but=errpipe_write) if cwd is not None: os.chdir(cwd) # This is a copy of Python/pythonrun.c # _Py_RestoreSignals(). If that were exposed # as a sys._py_restoresignals func it would be # better.. but this pure python implementation # isn't likely to be used much anymore. if restore_signals: signals = ('SIGPIPE', 'SIGXFZ', 'SIGXFSZ') for sig in signals: if hasattr(signal, sig): signal.signal(getattr(signal, sig), signal.SIG_DFL) if start_new_session and hasattr(os, 'setsid'): os.setsid() if preexec_fn: preexec_fn() if env is None: os.execvp(executable, args) else: os.execvpe(executable, args, env) except: try: exc_type, exc_value = sys.exc_info()[:2] if isinstance(exc_value, OSError): errno_num = exc_value.errno else: errno_num = 0 message = '%s:%x:%s' % (exc_type.__name__, errno_num, exc_value) message = message.encode(errors="surrogatepass") os.write(errpipe_write, message) except Exception: # We MUST not allow anything odd happening # above to prevent us from exiting below. pass # This exitcode won't be reported to applications # so it really doesn't matter what we return. os._exit(255) # Parent if gc_was_enabled: gc.enable() finally: # be sure the FD is closed no matter what os.close(errpipe_write) if p2cread != -1 and p2cwrite != -1: os.close(p2cread) if c2pwrite != -1 and c2pread != -1: os.close(c2pwrite) if errwrite != -1 and errread != -1: os.close(errwrite) # Wait for exec to fail or succeed; possibly raising an # exception (limited in size) data = bytearray() while True: part = _eintr_retry_call(os.read, errpipe_read, 50000) data += part if not part or len(data) > 50000: break finally: # be sure the FD is closed no matter what os.close(errpipe_read) if data: _eintr_retry_call(os.waitpid, self.pid, 0) try: exception_name, hex_errno, err_msg = data.split(b':', 2) except ValueError: print('Bad exception data:', repr(data)) exception_name = b'RuntimeError' hex_errno = b'0' err_msg = b'Unknown' child_exception_type = getattr( builtins, exception_name.decode('ascii'), RuntimeError) for fd in (p2cwrite, c2pread, errread): if fd != -1: os.close(fd) err_msg = err_msg.decode(errors="surrogatepass") if issubclass(child_exception_type, OSError) and hex_errno: errno_num = int(hex_errno, 16) if errno_num != 0: err_msg = os.strerror(errno_num) if errno_num == errno.ENOENT: err_msg += ': ' + repr(args[0]) raise child_exception_type(errno_num, err_msg) raise child_exception_type(err_msg) def _handle_exitstatus(self, sts, _WIFSIGNALED=os.WIFSIGNALED, _WTERMSIG=os.WTERMSIG, _WIFEXITED=os.WIFEXITED, _WEXITSTATUS=os.WEXITSTATUS): # This method is called (indirectly) by __del__, so it cannot # refer to anything outside of its local scope.""" if _WIFSIGNALED(sts): self.returncode = -_WTERMSIG(sts) elif _WIFEXITED(sts): self.returncode = _WEXITSTATUS(sts) else: # Should never happen raise RuntimeError("Unknown child exit status!") def _internal_poll(self, _deadstate=None, _waitpid=os.waitpid, _WNOHANG=os.WNOHANG, _os_error=os.error): """Check if child process has terminated. Returns returncode attribute. This method is called by __del__, so it cannot reference anything outside of the local scope (nor can any methods it calls). """ if self.returncode is None: try: pid, sts = _waitpid(self.pid, _WNOHANG) if pid == self.pid: self._handle_exitstatus(sts) except _os_error: if _deadstate is not None: self.returncode = _deadstate return self.returncode def wait(self): """Wait for child process to terminate. Returns returncode attribute.""" if self.returncode is None: pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0) self._handle_exitstatus(sts) return self.returncode def _communicate(self, input): if self.stdin: # Flush stdio buffer. This might block, if the user has # been writing to .stdin in an uncontrolled fashion. self.stdin.flush() if not input: self.stdin.close() if _has_poll: stdout, stderr = self._communicate_with_poll(input) else: stdout, stderr = self._communicate_with_select(input) # All data exchanged. Translate lists into strings. if stdout is not None: stdout = b''.join(stdout) if stderr is not None: stderr = b''.join(stderr) # Translate newlines, if requested. # This also turns bytes into strings. if self.universal_newlines: if stdout is not None: stdout = self._translate_newlines(stdout, self.stdout.encoding) if stderr is not None: stderr = self._translate_newlines(stderr, self.stderr.encoding) self.wait() return (stdout, stderr) def _communicate_with_poll(self, input): stdout = None # Return stderr = None # Return fd2file = {} fd2output = {} poller = select.poll() def register_and_append(file_obj, eventmask): poller.register(file_obj.fileno(), eventmask) fd2file[file_obj.fileno()] = file_obj def close_unregister_and_remove(fd): poller.unregister(fd) fd2file[fd].close() fd2file.pop(fd) if self.stdin and input: register_and_append(self.stdin, select.POLLOUT) select_POLLIN_POLLPRI = select.POLLIN | select.POLLPRI if self.stdout: register_and_append(self.stdout, select_POLLIN_POLLPRI) fd2output[self.stdout.fileno()] = stdout = [] if self.stderr: register_and_append(self.stderr, select_POLLIN_POLLPRI) fd2output[self.stderr.fileno()] = stderr = [] input_offset = 0 while fd2file: try: ready = poller.poll() except select.error as e: if e.args[0] == errno.EINTR: continue raise # XXX Rewrite these to use non-blocking I/O on the # file objects; they are no longer using C stdio! for fd, mode in ready: if mode & select.POLLOUT: chunk = input[input_offset : input_offset + _PIPE_BUF] input_offset += os.write(fd, chunk) if input_offset >= len(input): close_unregister_and_remove(fd) elif mode & select_POLLIN_POLLPRI: data = os.read(fd, 4096) if not data: close_unregister_and_remove(fd) fd2output[fd].append(data) else: # Ignore hang up or errors. close_unregister_and_remove(fd) return (stdout, stderr) def _communicate_with_select(self, input): read_set = [] write_set = [] stdout = None # Return stderr = None # Return if self.stdin and input: write_set.append(self.stdin) if self.stdout: read_set.append(self.stdout) stdout = [] if self.stderr: read_set.append(self.stderr) stderr = [] input_offset = 0 while read_set or write_set: try: rlist, wlist, xlist = select.select(read_set, write_set, []) except select.error as e: if e.args[0] == errno.EINTR: continue raise # XXX Rewrite these to use non-blocking I/O on the # file objects; they are no longer using C stdio! if self.stdin in wlist: chunk = input[input_offset : input_offset + _PIPE_BUF] bytes_written = os.write(self.stdin.fileno(), chunk) input_offset += bytes_written if input_offset >= len(input): self.stdin.close() write_set.remove(self.stdin) if self.stdout in rlist: data = os.read(self.stdout.fileno(), 1024) if not data: self.stdout.close() read_set.remove(self.stdout) stdout.append(data) if self.stderr in rlist: data = os.read(self.stderr.fileno(), 1024) if not data: self.stderr.close() read_set.remove(self.stderr) stderr.append(data) return (stdout, stderr) def send_signal(self, sig): """Send a signal to the process """ os.kill(self.pid, sig) def terminate(self): """Terminate the process with SIGTERM """ self.send_signal(signal.SIGTERM) def kill(self): """Kill the process with SIGKILL """ self.send_signal(signal.SIGKILL) def _demo_posix(): # # Example 1: Simple redirection: Get process list # plist = Popen(["ps"], stdout=PIPE).communicate()[0] print("Process list:") print(plist) # # Example 2: Change uid before executing child # if os.getuid() == 0: p = Popen(["id"], preexec_fn=lambda: os.setuid(100)) p.wait() # # Example 3: Connecting several subprocesses # print("Looking for 'hda'...") p1 = Popen(["dmesg"], stdout=PIPE) p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE) print(repr(p2.communicate()[0])) # # Example 4: Catch execution error # print() print("Trying a weird file...") try: print(Popen(["/this/path/does/not/exist"]).communicate()) except OSError as e: if e.errno == errno.ENOENT: print("The file didn't exist. I thought so...") print("Child traceback:") print(e.child_traceback) else: print("Error", e.errno) else: print("Gosh. No error.", file=sys.stderr) def _demo_windows(): # # Example 1: Connecting several subprocesses # print("Looking for 'PROMPT' in set output...") p1 = Popen("set", stdout=PIPE, shell=True) p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE) print(repr(p2.communicate()[0])) # # Example 2: Simple execution of program # print("Executing calc...") p = Popen("calc") p.wait() if __name__ == "__main__": if mswindows: _demo_windows() else: _demo_posix()