1 # subprocess - Subprocesses with accessible I/O streams
3 # For more information about this module, see PEP 324.
5 # This module should remain compatible with Python 2.2, see PEP 291.
7 # Copyright (c) 2003-2005 by Peter Astrand <astrand@lysator.liu.se>
9 # Licensed to PSF under a Contributor Agreement.
10 # See http://www.python.org/2.4/license for licensing details.
12 r"""subprocess - Subprocesses with accessible I/O streams
14 This module allows you to spawn processes, connect to their
15 input/output/error pipes, and obtain their return codes. This module
16 intends to replace several other, older modules and functions, like:
24 Information about how the subprocess module can be used to replace these
25 modules and functions can be found below.
29 Using the subprocess module
30 ===========================
31 This module defines one class called Popen:
33 class Popen(args, bufsize=0, executable=None,
34 stdin=None, stdout=None, stderr=None,
35 preexec_fn=None, close_fds=False, shell=False,
36 cwd=None, env=None, universal_newlines=False,
37 startupinfo=None, creationflags=0):
42 args should be a string, or a sequence of program arguments. The
43 program to execute is normally the first item in the args sequence or
44 string, but can be explicitly set by using the executable argument.
46 On UNIX, with shell=False (default): In this case, the Popen class
47 uses os.execvp() to execute the child program. args should normally
48 be a sequence. A string will be treated as a sequence with the string
49 as the only item (the program to execute).
51 On UNIX, with shell=True: If args is a string, it specifies the
52 command string to execute through the shell. If args is a sequence,
53 the first item specifies the command string, and any additional items
54 will be treated as additional shell arguments.
56 On Windows: the Popen class uses CreateProcess() to execute the child
57 program, which operates on strings. If args is a sequence, it will be
58 converted to a string using the list2cmdline method. Please note that
59 not all MS Windows applications interpret the command line the same
60 way: The list2cmdline is designed for applications using the same
61 rules as the MS C runtime.
63 bufsize, if given, has the same meaning as the corresponding argument
64 to the built-in open() function: 0 means unbuffered, 1 means line
65 buffered, any other positive value means use a buffer of
66 (approximately) that size. A negative bufsize means to use the system
67 default, which usually means fully buffered. The default value for
68 bufsize is 0 (unbuffered).
70 stdin, stdout and stderr specify the executed programs' standard
71 input, standard output and standard error file handles, respectively.
72 Valid values are PIPE, an existing file descriptor (a positive
73 integer), an existing file object, and None. PIPE indicates that a
74 new pipe to the child should be created. With None, no redirection
75 will occur; the child's file handles will be inherited from the
76 parent. Additionally, stderr can be STDOUT, which indicates that the
77 stderr data from the applications should be captured into the same
78 file handle as for stdout.
80 If preexec_fn is set to a callable object, this object will be called
81 in the child process just before the child is executed.
83 If close_fds is true, all file descriptors except 0, 1 and 2 will be
84 closed before the child process is executed.
86 if shell is true, the specified command will be executed through the
89 If cwd is not None, the current directory will be changed to cwd
90 before the child is executed.
92 If env is not None, it defines the environment variables for the new
95 If universal_newlines is true, the file objects stdout and stderr are
96 opened as a text files, but lines may be terminated by any of '\n',
97 the Unix end-of-line convention, '\r', the Macintosh convention or
98 '\r\n', the Windows convention. All of these external representations
99 are seen as '\n' by the Python program. Note: This feature is only
100 available if Python is built with universal newline support (the
101 default). Also, the newlines attribute of the file objects stdout,
102 stdin and stderr are not updated by the communicate() method.
104 The startupinfo and creationflags, if given, will be passed to the
105 underlying CreateProcess() function. They can specify things such as
106 appearance of the main window and priority for the new process.
110 This module also defines two shortcut functions:
112 call(*popenargs, **kwargs):
113 Run command with arguments. Wait for command to complete, then
114 return the returncode attribute.
116 The arguments are the same as for the Popen constructor. Example:
118 retcode = call(["ls", "-l"])
120 check_call(*popenargs, **kwargs):
121 Run command with arguments. Wait for command to complete. If the
122 exit code was zero then return, otherwise raise
123 CalledProcessError. The CalledProcessError object will have the
124 return code in the returncode attribute.
126 The arguments are the same as for the Popen constructor. Example:
128 check_call(["ls", "-l"])
132 Exceptions raised in the child process, before the new program has
133 started to execute, will be re-raised in the parent. Additionally,
134 the exception object will have one extra attribute called
135 'child_traceback', which is a string containing traceback information
136 from the childs point of view.
138 The most common exception raised is OSError. This occurs, for
139 example, when trying to execute a non-existent file. Applications
140 should prepare for OSErrors.
142 A ValueError will be raised if Popen is called with invalid arguments.
144 check_call() will raise CalledProcessError, if the called process
145 returns a non-zero return code.
150 Unlike some other popen functions, this implementation will never call
151 /bin/sh implicitly. This means that all characters, including shell
152 metacharacters, can safely be passed to child processes.
157 Instances of the Popen class have the following methods:
160 Check if child process has terminated. Returns returncode
164 Wait for child process to terminate. Returns returncode attribute.
166 communicate(input=None)
167 Interact with process: Send data to stdin. Read data from stdout
168 and stderr, until end-of-file is reached. Wait for process to
169 terminate. The optional stdin argument should be a string to be
170 sent to the child process, or None, if no data should be sent to
173 communicate() returns a tuple (stdout, stderr).
175 Note: The data read is buffered in memory, so do not use this
176 method if the data size is large or unlimited.
178 The following attributes are also available:
181 If the stdin argument is PIPE, this attribute is a file object
182 that provides input to the child process. Otherwise, it is None.
185 If the stdout argument is PIPE, this attribute is a file object
186 that provides output from the child process. Otherwise, it is
190 If the stderr argument is PIPE, this attribute is file object that
191 provides error output from the child process. Otherwise, it is
195 The process ID of the child process.
198 The child return code. A None value indicates that the process
199 hasn't terminated yet. A negative value -N indicates that the
200 child was terminated by signal N (UNIX only).
203 Replacing older functions with the subprocess module
204 ====================================================
205 In this section, "a ==> b" means that b can be used as a replacement
208 Note: All functions in this section fail (more or less) silently if
209 the executed program cannot be found; this module raises an OSError
212 In the following examples, we assume that the subprocess module is
213 imported with "from subprocess import *".
216 Replacing /bin/sh shell backquote
217 ---------------------------------
220 output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
223 Replacing shell pipe line
224 -------------------------
225 output=`dmesg | grep hda`
227 p1 = Popen(["dmesg"], stdout=PIPE)
228 p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
229 output = p2.communicate()[0]
232 Replacing os.system()
233 ---------------------
234 sts = os.system("mycmd" + " myarg")
236 p = Popen("mycmd" + " myarg", shell=True)
237 pid, sts = os.waitpid(p.pid, 0)
241 * Calling the program through the shell is usually not required.
243 * It's easier to look at the returncode attribute than the
246 A more real-world example would look like this:
249 retcode = call("mycmd" + " myarg", shell=True)
251 print >>sys.stderr, "Child was terminated by signal", -retcode
253 print >>sys.stderr, "Child returned", retcode
255 print >>sys.stderr, "Execution failed:", e
262 pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
264 pid = Popen(["/bin/mycmd", "myarg"]).pid
269 retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
271 retcode = call(["/bin/mycmd", "myarg"])
276 os.spawnvp(os.P_NOWAIT, path, args)
278 Popen([path] + args[1:])
283 os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
285 Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
290 pipe = os.popen(cmd, mode='r', bufsize)
292 pipe = Popen(cmd, shell=True, bufsize=bufsize, stdout=PIPE).stdout
294 pipe = os.popen(cmd, mode='w', bufsize)
296 pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin
299 (child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize)
301 p = Popen(cmd, shell=True, bufsize=bufsize,
302 stdin=PIPE, stdout=PIPE, close_fds=True)
303 (child_stdin, child_stdout) = (p.stdin, p.stdout)
308 child_stderr) = os.popen3(cmd, mode, bufsize)
310 p = Popen(cmd, shell=True, bufsize=bufsize,
311 stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
314 child_stderr) = (p.stdin, p.stdout, p.stderr)
317 (child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize)
319 p = Popen(cmd, shell=True, bufsize=bufsize,
320 stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
321 (child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
326 Note: If the cmd argument to popen2 functions is a string, the command
327 is executed through /bin/sh. If it is a list, the command is directly
330 (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
332 p = Popen(["somestring"], shell=True, bufsize=bufsize
333 stdin=PIPE, stdout=PIPE, close_fds=True)
334 (child_stdout, child_stdin) = (p.stdout, p.stdin)
337 (child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode)
339 p = Popen(["mycmd", "myarg"], bufsize=bufsize,
340 stdin=PIPE, stdout=PIPE, close_fds=True)
341 (child_stdout, child_stdin) = (p.stdout, p.stdin)
343 The popen2.Popen3 and popen3.Popen4 basically works as subprocess.Popen,
346 * subprocess.Popen raises an exception if the execution fails
347 * the capturestderr argument is replaced with the stderr argument.
348 * stdin=PIPE and stdout=PIPE must be specified.
349 * popen2 closes all filedescriptors by default, but you have to specify
350 close_fds=True with subprocess.Popen.
356 mswindows = (sys.platform == "win32")
362 # Exception classes used by this module.
363 class CalledProcessError(Exception):
364 """This exception is raised when a process run by check_call() returns
365 a non-zero exit status. The exit status will be stored in the
366 returncode attribute."""
367 def __init__(self, returncode, cmd):
368 self.returncode = returncode
371 return "Command '%s' returned non-zero exit status %d" % (self.cmd, self.returncode)
378 # SCons: the threading module is only used by the communicate()
379 # method, which we don't actually use, so don't worry if we
384 # Try to get _subprocess
385 from _subprocess import *
386 class STARTUPINFO(object):
392 class pywintypes(object):
395 # If not there, then drop back to requiring pywin32
396 # TODO: Should this be wrapped in try as well? To notify user to install
397 # pywin32 ? With URL to it?
399 from win32api import GetStdHandle, STD_INPUT_HANDLE, \
400 STD_OUTPUT_HANDLE, STD_ERROR_HANDLE
401 from win32api import GetCurrentProcess, DuplicateHandle, \
402 GetModuleFileName, GetVersion
403 from win32con import DUPLICATE_SAME_ACCESS, SW_HIDE
404 from win32pipe import CreatePipe
405 from win32process import CreateProcess, STARTUPINFO, \
406 GetExitCodeProcess, STARTF_USESTDHANDLES, \
407 STARTF_USESHOWWINDOW, CREATE_NEW_CONSOLE
408 from win32event import WaitForSingleObject, INFINITE, WAIT_OBJECT_0
419 except AttributeError:
424 except AttributeError:
427 __all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "CalledProcessError"]
430 MAXFD = os.sysconf("SC_OPEN_MAX")
431 except KeyboardInterrupt:
432 raise # SCons: don't swallow keyboard interrupts
440 return isinstance(obj, type(1))
441 def is_int_or_long(obj):
442 return type(obj) in (type(1), type(1L))
445 return isinstance(obj, int)
446 def is_int_or_long(obj):
447 return isinstance(obj, (int, long))
451 except AttributeError:
453 types.StringTypes = (str, unicode)
455 types.StringTypes = (str,)
457 return isinstance(obj, types.StringTypes)
462 for inst in _active[:]:
463 if inst.poll(_deadstate=sys.maxsize) >= 0:
467 # This can happen if two threads create a new Popen instance.
468 # It's harmless that it was already removed, so ignore.
475 def call(*popenargs, **kwargs):
476 """Run command with arguments. Wait for command to complete, then
477 return the returncode attribute.
479 The arguments are the same as for the Popen constructor. Example:
481 retcode = call(["ls", "-l"])
483 return apply(Popen, popenargs, kwargs).wait()
486 def check_call(*popenargs, **kwargs):
487 """Run command with arguments. Wait for command to complete. If
488 the exit code was zero then return, otherwise raise
489 CalledProcessError. The CalledProcessError object will have the
490 return code in the returncode attribute.
492 The arguments are the same as for the Popen constructor. Example:
494 check_call(["ls", "-l"])
496 retcode = call(*popenargs, **kwargs)
497 cmd = kwargs.get("args")
501 raise CalledProcessError(retcode, cmd)
505 def list2cmdline(seq):
507 Translate a sequence of arguments into a command line
508 string, using the same rules as the MS C runtime:
510 1) Arguments are delimited by white space, which is either a
513 2) A string surrounded by double quotation marks is
514 interpreted as a single argument, regardless of white space
515 contained within. A quoted string can be embedded in an
518 3) A double quotation mark preceded by a backslash is
519 interpreted as a literal double quotation mark.
521 4) Backslashes are interpreted literally, unless they
522 immediately precede a double quotation mark.
524 5) If backslashes immediately precede a double quotation mark,
525 every pair of backslashes is interpreted as a literal
526 backslash. If the number of backslashes is odd, the last
527 backslash escapes the next double quotation mark as
532 # http://msdn.microsoft.com/library/en-us/vccelng/htm/progs_12.asp
538 # Add a space to separate this argument from the others
542 needquote = (" " in arg) or ("\t" in arg)
548 # Don't know if we need to double yet.
552 result.append('\\' * len(bs_buf)*2)
558 result.extend(bs_buf)
562 # Add remaining backspaces, if any.
564 result.extend(bs_buf)
567 result.extend(bs_buf)
570 return ''.join(result)
573 def __init__(self, args, bufsize=0, executable=None,
574 stdin=None, stdout=None, stderr=None,
575 preexec_fn=None, close_fds=False, shell=False,
576 cwd=None, env=None, universal_newlines=False,
577 startupinfo=None, creationflags=0):
578 """Create new Popen instance."""
581 self._child_created = False
582 if not is_int_or_long(bufsize):
583 raise TypeError("bufsize must be an integer")
586 if preexec_fn is not None:
587 raise ValueError("preexec_fn is not supported on Windows "
590 raise ValueError("close_fds is not supported on Windows "
594 if startupinfo is not None:
595 raise ValueError("startupinfo is only supported on Windows "
597 if creationflags != 0:
598 raise ValueError("creationflags is only supported on Windows "
605 self.returncode = None
606 self.universal_newlines = universal_newlines
608 # Input and output objects. The general principle is like
613 # p2cwrite ---stdin---> p2cread
614 # c2pread <--stdout--- c2pwrite
615 # errread <--stderr--- errwrite
617 # On POSIX, the child objects are file descriptors. On
618 # Windows, these are Windows file handles. The parent objects
619 # are file descriptors on both platforms. The parent objects
620 # are None when not using PIPEs. The child objects are None
621 # when not redirecting.
625 errread, errwrite) = self._get_handles(stdin, stdout, stderr)
627 self._execute_child(args, executable, preexec_fn, close_fds,
628 cwd, env, universal_newlines,
629 startupinfo, creationflags, shell,
635 self.stdin = os.fdopen(p2cwrite, 'wb', bufsize)
637 if universal_newlines:
638 self.stdout = os.fdopen(c2pread, 'rU', bufsize)
640 self.stdout = os.fdopen(c2pread, 'rb', bufsize)
642 if universal_newlines:
643 self.stderr = os.fdopen(errread, 'rU', bufsize)
645 self.stderr = os.fdopen(errread, 'rb', bufsize)
648 def _translate_newlines(self, data):
649 data = data.replace("\r\n", "\n")
650 data = data.replace("\r", "\n")
655 if not self._child_created:
656 # We didn't get to successfully create a child process.
658 # In case the child hasn't been waited on, check if it's done.
659 self.poll(_deadstate=sys.maxsize)
660 if self.returncode is None and _active is not None:
661 # Child is still running, keep us alive until we can wait on it.
665 def communicate(self, input=None):
666 """Interact with process: Send data to stdin. Read data from
667 stdout and stderr, until end-of-file is reached. Wait for
668 process to terminate. The optional input argument should be a
669 string to be sent to the child process, or None, if no data
670 should be sent to the child.
672 communicate() returns a tuple (stdout, stderr)."""
674 # Optimization: If we are only using one pipe, or no pipe at
675 # all, using select() or threads is unnecessary.
676 if [self.stdin, self.stdout, self.stderr].count(None) >= 2:
681 self.stdin.write(input)
684 stdout = self.stdout.read()
686 stderr = self.stderr.read()
688 return (stdout, stderr)
690 return self._communicate(input)
697 def _get_handles(self, stdin, stdout, stderr):
698 """Construct and return tupel with IO objects:
699 p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
701 if stdin is None and stdout is None and stderr is None:
702 return (None, None, None, None, None, None)
704 p2cread, p2cwrite = None, None
705 c2pread, c2pwrite = None, None
706 errread, errwrite = None, None
709 p2cread = GetStdHandle(STD_INPUT_HANDLE)
711 p2cread, p2cwrite = CreatePipe(None, 0)
712 # Detach and turn into fd
713 p2cwrite = p2cwrite.Detach()
714 p2cwrite = msvcrt.open_osfhandle(p2cwrite, 0)
716 p2cread = msvcrt.get_osfhandle(stdin)
718 # Assuming file-like object
719 p2cread = msvcrt.get_osfhandle(stdin.fileno())
720 p2cread = self._make_inheritable(p2cread)
723 c2pwrite = GetStdHandle(STD_OUTPUT_HANDLE)
725 c2pread, c2pwrite = CreatePipe(None, 0)
726 # Detach and turn into fd
727 c2pread = c2pread.Detach()
728 c2pread = msvcrt.open_osfhandle(c2pread, 0)
730 c2pwrite = msvcrt.get_osfhandle(stdout)
732 # Assuming file-like object
733 c2pwrite = msvcrt.get_osfhandle(stdout.fileno())
734 c2pwrite = self._make_inheritable(c2pwrite)
737 errwrite = GetStdHandle(STD_ERROR_HANDLE)
739 errread, errwrite = CreatePipe(None, 0)
740 # Detach and turn into fd
741 errread = errread.Detach()
742 errread = msvcrt.open_osfhandle(errread, 0)
743 elif stderr == STDOUT:
746 errwrite = msvcrt.get_osfhandle(stderr)
748 # Assuming file-like object
749 errwrite = msvcrt.get_osfhandle(stderr.fileno())
750 errwrite = self._make_inheritable(errwrite)
752 return (p2cread, p2cwrite,
757 def _make_inheritable(self, handle):
758 """Return a duplicate of handle, which is inheritable"""
759 return DuplicateHandle(GetCurrentProcess(), handle,
760 GetCurrentProcess(), 0, 1,
761 DUPLICATE_SAME_ACCESS)
764 def _find_w9xpopen(self):
765 """Find and return absolut path to w9xpopen.exe"""
766 w9xpopen = os.path.join(os.path.dirname(GetModuleFileName(0)),
768 if not os.path.exists(w9xpopen):
769 # Eeek - file-not-found - possibly an embedding
770 # situation - see if we can locate it in sys.exec_prefix
771 w9xpopen = os.path.join(os.path.dirname(sys.exec_prefix),
773 if not os.path.exists(w9xpopen):
774 raise RuntimeError("Cannot locate w9xpopen.exe, which is "
775 "needed for Popen to work with your "
776 "shell or platform.")
780 def _execute_child(self, args, executable, preexec_fn, close_fds,
781 cwd, env, universal_newlines,
782 startupinfo, creationflags, shell,
786 """Execute program (MS Windows version)"""
788 if not isinstance(args, types.StringTypes):
789 args = list2cmdline(args)
791 # Process startup details
792 if startupinfo is None:
793 startupinfo = STARTUPINFO()
794 if None not in (p2cread, c2pwrite, errwrite):
795 startupinfo.dwFlags = startupinfo.dwFlags | STARTF_USESTDHANDLES
796 startupinfo.hStdInput = p2cread
797 startupinfo.hStdOutput = c2pwrite
798 startupinfo.hStdError = errwrite
801 startupinfo.dwFlags = startupinfo.dwFlags | STARTF_USESHOWWINDOW
802 startupinfo.wShowWindow = SW_HIDE
803 comspec = os.environ.get("COMSPEC", "cmd.exe")
804 args = comspec + " /c " + args
805 if (GetVersion() >= 0x80000000L or
806 os.path.basename(comspec).lower() == "command.com"):
807 # Win9x, or using command.com on NT. We need to
808 # use the w9xpopen intermediate program. For more
809 # information, see KB Q150956
810 # (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp)
811 w9xpopen = self._find_w9xpopen()
812 args = '"%s" %s' % (w9xpopen, args)
813 # Not passing CREATE_NEW_CONSOLE has been known to
814 # cause random failures on win9x. Specifically a
815 # dialog: "Your program accessed mem currently in
816 # use at xxx" and a hopeful warning about the
817 # stability of your system. Cost is Ctrl+C wont
819 creationflags = creationflags | CREATE_NEW_CONSOLE
823 hp, ht, pid, tid = CreateProcess(executable, args,
824 # no special security
826 # must inherit handles to pass std
833 except pywintypes.error, e:
834 # Translate pywintypes.error to WindowsError, which is
835 # a subclass of OSError. FIXME: We should really
836 # translate errno using _sys_errlist (or simliar), but
837 # how can this be done from Python?
838 raise WindowsError(*e.args)
840 # Retain the process handle, but close the thread handle
841 self._child_created = True
846 # Child is launched. Close the parent's copy of those pipe
847 # handles that only the child should have open. You need
848 # to make sure that no handles to the write end of the
849 # output pipe are maintained in this process or else the
850 # pipe will not close when the child process exits and the
851 # ReadFile will hang.
852 if p2cread is not None:
854 if c2pwrite is not None:
856 if errwrite is not None:
860 def poll(self, _deadstate=None):
861 """Check if child process has terminated. Returns returncode
863 if self.returncode is None:
864 if WaitForSingleObject(self._handle, 0) == WAIT_OBJECT_0:
865 self.returncode = GetExitCodeProcess(self._handle)
866 return self.returncode
870 """Wait for child process to terminate. Returns returncode
872 if self.returncode is None:
873 obj = WaitForSingleObject(self._handle, INFINITE)
874 self.returncode = GetExitCodeProcess(self._handle)
875 return self.returncode
878 def _readerthread(self, fh, buffer):
879 buffer.append(fh.read())
882 def _communicate(self, input):
883 stdout = None # Return
884 stderr = None # Return
888 stdout_thread = threading.Thread(target=self._readerthread,
889 args=(self.stdout, stdout))
890 stdout_thread.setDaemon(True)
891 stdout_thread.start()
894 stderr_thread = threading.Thread(target=self._readerthread,
895 args=(self.stderr, stderr))
896 stderr_thread.setDaemon(True)
897 stderr_thread.start()
900 if input is not None:
901 self.stdin.write(input)
909 # All data exchanged. Translate lists into strings.
910 if stdout is not None:
912 if stderr is not None:
915 # Translate newlines, if requested. We cannot let the file
916 # object do the translation: It is based on stdio, which is
917 # impossible to combine with select (unless forcing no
919 if self.universal_newlines and hasattr(file, 'newlines'):
921 stdout = self._translate_newlines(stdout)
923 stderr = self._translate_newlines(stderr)
926 return (stdout, stderr)
932 def _get_handles(self, stdin, stdout, stderr):
933 """Construct and return tupel with IO objects:
934 p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
936 p2cread, p2cwrite = None, None
937 c2pread, c2pwrite = None, None
938 errread, errwrite = None, None
943 p2cread, p2cwrite = os.pipe()
947 # Assuming file-like object
948 p2cread = stdin.fileno()
953 c2pread, c2pwrite = os.pipe()
957 # Assuming file-like object
958 c2pwrite = stdout.fileno()
963 errread, errwrite = os.pipe()
964 elif stderr == STDOUT:
969 # Assuming file-like object
970 errwrite = stderr.fileno()
972 return (p2cread, p2cwrite,
977 def _set_cloexec_flag(self, fd):
979 cloexec_flag = fcntl.FD_CLOEXEC
980 except AttributeError:
983 old = fcntl.fcntl(fd, fcntl.F_GETFD)
984 fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag)
987 def _close_fds(self, but):
988 for i in range(3, MAXFD):
993 except KeyboardInterrupt:
994 raise # SCons: don't swallow keyboard interrupts
999 def _execute_child(self, args, executable, preexec_fn, close_fds,
1000 cwd, env, universal_newlines,
1001 startupinfo, creationflags, shell,
1005 """Execute program (POSIX version)"""
1011 args = ["/bin/sh", "-c"] + args
1013 if executable is None:
1014 executable = args[0]
1016 # For transferring possible exec failure from child to parent
1017 # The first char specifies the exception type: 0 means
1018 # OSError, 1 means some other error.
1019 errpipe_read, errpipe_write = os.pipe()
1020 self._set_cloexec_flag(errpipe_write)
1022 self.pid = os.fork()
1023 self._child_created = True
1027 # Close parent's pipe ends
1034 os.close(errpipe_read)
1040 os.dup2(c2pwrite, 1)
1042 os.dup2(errwrite, 2)
1044 # Close pipe fds. Make sure we don't close the same
1045 # fd more than once, or standard fds.
1049 # Fall-back for earlier Python versions, so epydoc
1050 # can use this module directly to execute things.
1053 if c2pwrite and c2pwrite not in (p2cread,):
1055 if errwrite and errwrite not in (p2cread, c2pwrite):
1058 for fd in set((p2cread, c2pwrite, errwrite))-set((0,1,2)):
1061 # Close all other fds, if asked for
1063 self._close_fds(but=errpipe_write)
1072 os.execvp(executable, args)
1074 os.execvpe(executable, args, env)
1076 except KeyboardInterrupt:
1077 raise # SCons: don't swallow keyboard interrupts
1080 exc_type, exc_value, tb = sys.exc_info()
1081 # Save the traceback and attach it to the exception object
1082 exc_lines = traceback.format_exception(exc_type,
1085 exc_value.child_traceback = ''.join(exc_lines)
1086 os.write(errpipe_write, pickle.dumps(exc_value))
1088 # This exitcode won't be reported to applications, so it
1089 # really doesn't matter what we return.
1093 os.close(errpipe_write)
1094 if p2cread and p2cwrite:
1096 if c2pwrite and c2pread:
1098 if errwrite and errread:
1101 # Wait for exec to fail or succeed; possibly raising exception
1102 data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB
1103 os.close(errpipe_read)
1105 os.waitpid(self.pid, 0)
1106 child_exception = pickle.loads(data)
1107 raise child_exception
1110 def _handle_exitstatus(self, sts):
1111 if os.WIFSIGNALED(sts):
1112 self.returncode = -os.WTERMSIG(sts)
1113 elif os.WIFEXITED(sts):
1114 self.returncode = os.WEXITSTATUS(sts)
1116 # Should never happen
1117 raise RuntimeError("Unknown child exit status!")
1120 def poll(self, _deadstate=None):
1121 """Check if child process has terminated. Returns returncode
1123 if self.returncode is None:
1125 pid, sts = os.waitpid(self.pid, os.WNOHANG)
1127 self._handle_exitstatus(sts)
1129 if _deadstate is not None:
1130 self.returncode = _deadstate
1131 return self.returncode
1135 """Wait for child process to terminate. Returns returncode
1137 if self.returncode is None:
1138 pid, sts = os.waitpid(self.pid, 0)
1139 self._handle_exitstatus(sts)
1140 return self.returncode
1143 def _communicate(self, input):
1146 stdout = None # Return
1147 stderr = None # Return
1150 # Flush stdio buffer. This might block, if the user has
1151 # been writing to .stdin in an uncontrolled fashion.
1154 write_set.append(self.stdin)
1158 read_set.append(self.stdout)
1161 read_set.append(self.stderr)
1165 while read_set or write_set:
1166 rlist, wlist, xlist = select.select(read_set, write_set, [])
1168 if self.stdin in wlist:
1169 # When select has indicated that the file is writable,
1170 # we can write up to PIPE_BUF bytes without risk
1171 # blocking. POSIX defines PIPE_BUF >= 512
1172 m = memoryview(input)[input_offset:input_offset+512]
1173 bytes_written = os.write(self.stdin.fileno(), m)
1174 input_offset = input_offset + bytes_written
1175 if input_offset >= len(input):
1177 write_set.remove(self.stdin)
1179 if self.stdout in rlist:
1180 data = os.read(self.stdout.fileno(), 1024)
1183 read_set.remove(self.stdout)
1186 if self.stderr in rlist:
1187 data = os.read(self.stderr.fileno(), 1024)
1190 read_set.remove(self.stderr)
1193 # All data exchanged. Translate lists into strings.
1194 if stdout is not None:
1195 stdout = ''.join(stdout)
1196 if stderr is not None:
1197 stderr = ''.join(stderr)
1199 # Translate newlines, if requested. We cannot let the file
1200 # object do the translation: It is based on stdio, which is
1201 # impossible to combine with select (unless forcing no
1203 if self.universal_newlines and hasattr(file, 'newlines'):
1205 stdout = self._translate_newlines(stdout)
1207 stderr = self._translate_newlines(stderr)
1210 return (stdout, stderr)
1215 # Example 1: Simple redirection: Get process list
1217 plist = Popen(["ps"], stdout=PIPE).communicate()[0]
1218 print "Process list:"
1222 # Example 2: Change uid before executing child
1224 if os.getuid() == 0:
1225 p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
1229 # Example 3: Connecting several subprocesses
1231 print "Looking for 'hda'..."
1232 p1 = Popen(["dmesg"], stdout=PIPE)
1233 p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
1234 print repr(p2.communicate()[0])
1237 # Example 4: Catch execution error
1240 print "Trying a weird file..."
1242 print Popen(["/this/path/does/not/exist"]).communicate()
1244 if e.errno == errno.ENOENT:
1245 print "The file didn't exist. I thought so..."
1246 print "Child traceback:"
1247 print e.child_traceback
1249 print "Error", e.errno
1251 sys.stderr.write( "Gosh. No error.\n" )
1254 def _demo_windows():
1256 # Example 1: Connecting several subprocesses
1258 print "Looking for 'PROMPT' in set output..."
1259 p1 = Popen("set", stdout=PIPE, shell=True)
1260 p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
1261 print repr(p2.communicate()[0])
1264 # Example 2: Simple execution of program
1266 print "Executing calc..."
1271 if __name__ == "__main__":
1279 # indent-tabs-mode:nil
1281 # vim: set expandtab tabstop=4 shiftwidth=4: