certmaster/sub_process.py

   1 # subprocess - Subprocesses with accessible I/O streams
   2 #
   3 # For more information about this module, see PEP 324.
   4 #
   5 # This module should remain compatible with Python 2.2, see PEP 291.
   6 #
   7 # Copyright (c) 2003-2005 by Peter Astrand <astrand@lysator.liu.se>
   8 #
   9 # Licensed to PSF under a Contributor Agreement.
  10 # See http://www.python.org/2.4/license for licensing details.
  11
  12 r"""subprocess - Subprocesses with accessible I/O streams
  13
  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:
  17
  18 os.system
  19 os.spawn*
  20 os.popen*
  21 popen2.*
  22 commands.*
  23
  24 Information about how the subprocess module can be used to replace these
  25 modules and functions can be found below.
  26
  27
  28
  29 Using the subprocess module
  30 ===========================
  31 This module defines one class called Popen:
  32
  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):
  38
  39
  40 Arguments are:
  41
  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.
  45
  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).
  50
  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.
  55
  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.
  62
  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).
  69
  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.
  79
  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.
  82
  83 If close_fds is true, all file descriptors except 0, 1 and 2 will be
  84 closed before the child process is executed.
  85
  86 if shell is true, the specified command will be executed through the
  87 shell.
  88
  89 If cwd is not None, the current directory will be changed to cwd
  90 before the child is executed.
  91
  92 If env is not None, it defines the environment variables for the new
  93 process.
  94
  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.
 103
 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.
 107 (Windows only)
 108
 109
 110 This module also defines two shortcut functions:
 111
 112 call(*popenargs, **kwargs):
 113     Run command with arguments.  Wait for command to complete, then
 114     return the returncode attribute.
 115
 116     The arguments are the same as for the Popen constructor.  Example:
 117
 118     retcode = call(["ls", "-l"])
 119
 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.
 125
 126     The arguments are the same as for the Popen constructor.  Example:
 127
 128     check_call(["ls", "-l"])
 129
 130 Exceptions
 131 ----------
 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.
 137
 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.
 141
 142 A ValueError will be raised if Popen is called with invalid arguments.
 143
 144 check_call() will raise CalledProcessError, if the called process
 145 returns a non-zero return code.
 146
 147
 148 Security
 149 --------
 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.
 153
 154
 155 Popen objects
 156 =============
 157 Instances of the Popen class have the following methods:
 158
 159 poll()
 160     Check if child process has terminated.  Returns returncode
 161     attribute.
 162
 163 wait()
 164     Wait for child process to terminate.  Returns returncode attribute.
 165
 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
 171     the child.
 172
 173     communicate() returns a tuple (stdout, stderr).
 174
 175     Note: The data read is buffered in memory, so do not use this
 176     method if the data size is large or unlimited.
 177
 178 The following attributes are also available:
 179
 180 stdin
 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.
 183
 184 stdout
 185     If the stdout argument is PIPE, this attribute is a file object
 186     that provides output from the child process.  Otherwise, it is
 187     None.
 188
 189 stderr
 190     If the stderr argument is PIPE, this attribute is file object that
 191     provides error output from the child process.  Otherwise, it is
 192     None.
 193
 194 pid
 195     The process ID of the child process.
 196
 197 returncode
 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).
 201
 202
 203 Replacing older functions with the subprocess module
 204 ====================================================
 205 In this section, "a ==> b" means that b can be used as a replacement
 206 for a.
 207
 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
 210 exception.
 211
 212 In the following examples, we assume that the subprocess module is
 213 imported with "from subprocess import *".
 214
 215
 216 Replacing /bin/sh shell backquote
 217 ---------------------------------
 218 output=`mycmd myarg`
 219 ==>
 220 output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
 221
 222
 223 Replacing shell pipe line
 224 -------------------------
 225 output=`dmesg | grep hda`
 226 ==>
 227 p1 = Popen(["dmesg"], stdout=PIPE)
 228 p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
 229 output = p2.communicate()[0]
 230
 231
 232 Replacing os.system()
 233 ---------------------
 234 sts = os.system("mycmd" + " myarg")
 235 ==>
 236 p = Popen("mycmd" + " myarg", shell=True)
 237 pid, sts = os.waitpid(p.pid, 0)
 238
 239 Note:
 240
 241 * Calling the program through the shell is usually not required.
 242
 243 * It's easier to look at the returncode attribute than the
 244   exitstatus.
 245
 246 A more real-world example would look like this:
 247
 248 try:
 249     retcode = call("mycmd" + " myarg", shell=True)
 250     if retcode < 0:
 251         print >>sys.stderr, "Child was terminated by signal", -retcode
 252     else:
 253         print >>sys.stderr, "Child returned", retcode
 254 except OSError, e:
 255     print >>sys.stderr, "Execution failed:", e
 256
 257
 258 Replacing os.spawn*
 259 -------------------
 260 P_NOWAIT example:
 261
 262 pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
 263 ==>
 264 pid = Popen(["/bin/mycmd", "myarg"]).pid
 265
 266
 267 P_WAIT example:
 268
 269 retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
 270 ==>
 271 retcode = call(["/bin/mycmd", "myarg"])
 272
 273
 274 Vector example:
 275
 276 os.spawnvp(os.P_NOWAIT, path, args)
 277 ==>
 278 Popen([path] + args[1:])
 279
 280
 281 Environment example:
 282
 283 os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
 284 ==>
 285 Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
 286
 287
 288 Replacing os.popen*
 289 -------------------
 290 pipe = os.popen(cmd, mode='r', bufsize)
 291 ==>
 292 pipe = Popen(cmd, shell=True, bufsize=bufsize, stdout=PIPE).stdout
 293
 294 pipe = os.popen(cmd, mode='w', bufsize)
 295 ==>
 296 pipe = Popen(cmd, shell=True, bufsize=bufsize, stdin=PIPE).stdin
 297
 298
 299 (child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize)
 300 ==>
 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)
 304
 305
 306 (child_stdin,
 307  child_stdout,
 308  child_stderr) = os.popen3(cmd, mode, bufsize)
 309 ==>
 310 p = Popen(cmd, shell=True, bufsize=bufsize,
 311           stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
 312 (child_stdin,
 313  child_stdout,
 314  child_stderr) = (p.stdin, p.stdout, p.stderr)
 315
 316
 317 (child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize)
 318 ==>
 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)
 322
 323
 324 Replacing popen2.*
 325 ------------------
 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
 328 executed.
 329
 330 (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
 331 ==>
 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)
 335
 336
 337 (child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode)
 338 ==>
 339 p = Popen(["mycmd", "myarg"], bufsize=bufsize,
 340           stdin=PIPE, stdout=PIPE, close_fds=True)
 341 (child_stdout, child_stdin) = (p.stdout, p.stdin)
 342
 343 The popen2.Popen3 and popen3.Popen4 basically works as subprocess.Popen,
 344 except that:
 345
 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.
 351
 352
 353 """
 354
 355 import sys
 356 mswindows = (sys.platform == "win32")
 357
 358 import os
 359 import types
 360 import traceback
 361
 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
 369         self.cmd = cmd
 370     def __str__(self):
 371         return "Command '%s' returned non-zero exit status %d" % (self.cmd, self.returncode)
 372
 373
 374 if mswindows:
 375     import threading
 376     import msvcrt
 377     if 0: # <-- change this to use pywin32 instead of the _subprocess driver
 378         import pywintypes
 379         from win32api import GetStdHandle, STD_INPUT_HANDLE, \
 380                              STD_OUTPUT_HANDLE, STD_ERROR_HANDLE
 381         from win32api import GetCurrentProcess, DuplicateHandle, \
 382                              GetModuleFileName, GetVersion
 383         from win32con import DUPLICATE_SAME_ACCESS, SW_HIDE
 384         from win32pipe import CreatePipe
 385         from win32process import CreateProcess, STARTUPINFO, \
 386                                  GetExitCodeProcess, STARTF_USESTDHANDLES, \
 387                                  STARTF_USESHOWWINDOW, CREATE_NEW_CONSOLE
 388         from win32event import WaitForSingleObject, INFINITE, WAIT_OBJECT_0
 389     else:
 390         from _subprocess import *
 391         class STARTUPINFO:
 392             dwFlags = 0
 393             hStdInput = None
 394             hStdOutput = None
 395             hStdError = None
 396             wShowWindow = 0
 397         class pywintypes:
 398             error = IOError
 399 else:
 400     import select
 401     import errno
 402     import fcntl
 403     import pickle
 404
 405 __all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "CalledProcessError"]
 406
 407 try:
 408     MAXFD = os.sysconf("SC_OPEN_MAX")
 409 except:
 410     MAXFD = 256
 411
 412 # True/False does not exist on 2.2.0
 413 try:
 414     False
 415 except NameError:
 416     False = 0
 417     True = 1
 418
 419 _active = []
 420
 421 def _cleanup():
 422     for inst in _active[:]:
 423         if inst.poll(_deadstate=sys.maxint) >= 0:
 424             try:
 425                 _active.remove(inst)
 426             except ValueError:
 427                 # This can happen if two threads create a new Popen instance.
 428                 # It's harmless that it was already removed, so ignore.
 429                 pass
 430
 431 PIPE = -1
 432 STDOUT = -2
 433
 434
 435 def call(*popenargs, **kwargs):
 436     """Run command with arguments.  Wait for command to complete, then
 437     return the returncode attribute.
 438
 439     The arguments are the same as for the Popen constructor.  Example:
 440
 441     retcode = call(["ls", "-l"])
 442     """
 443     return Popen(*popenargs, **kwargs).wait()
 444
 445
 446 def check_call(*popenargs, **kwargs):
 447     """Run command with arguments.  Wait for command to complete.  If
 448     the exit code was zero then return, otherwise raise
 449     CalledProcessError.  The CalledProcessError object will have the
 450     return code in the returncode attribute.
 451
 452     The arguments are the same as for the Popen constructor.  Example:
 453
 454     check_call(["ls", "-l"])
 455     """
 456     retcode = call(*popenargs, **kwargs)
 457     cmd = kwargs.get("args")
 458     if cmd is None:
 459         cmd = popenargs[0]
 460     if retcode:
 461         raise CalledProcessError(retcode, cmd)
 462     return retcode
 463
 464
 465 def list2cmdline(seq):
 466     """
 467     Translate a sequence of arguments into a command line
 468     string, using the same rules as the MS C runtime:
 469
 470     1) Arguments are delimited by white space, which is either a
 471        space or a tab.
 472
 473     2) A string surrounded by double quotation marks is
 474        interpreted as a single argument, regardless of white space
 475        contained within.  A quoted string can be embedded in an
 476        argument.
 477
 478     3) A double quotation mark preceded by a backslash is
 479        interpreted as a literal double quotation mark.
 480
 481     4) Backslashes are interpreted literally, unless they
 482        immediately precede a double quotation mark.
 483
 484     5) If backslashes immediately precede a double quotation mark,
 485        every pair of backslashes is interpreted as a literal
 486        backslash.  If the number of backslashes is odd, the last
 487        backslash escapes the next double quotation mark as
 488        described in rule 3.
 489     """
 490
 491     # See
 492     # http://msdn.microsoft.com/library/en-us/vccelng/htm/progs_12.asp
 493     result = []
 494     needquote = False
 495     for arg in seq:
 496         bs_buf = []
 497
 498         # Add a space to separate this argument from the others
 499         if result:
 500             result.append(' ')
 501
 502         needquote = (" " in arg) or ("\t" in arg)
 503         if needquote:
 504             result.append('"')
 505
 506         for c in arg:
 507             if c == '\\':
 508                 # Don't know if we need to double yet.
 509                 bs_buf.append(c)
 510             elif c == '"':
 511                 # Double backspaces.
 512                 result.append('\\' * len(bs_buf)*2)
 513                 bs_buf = []
 514                 result.append('\\"')
 515             else:
 516                 # Normal char
 517                 if bs_buf:
 518                     result.extend(bs_buf)
 519                     bs_buf = []
 520                 result.append(c)
 521
 522         # Add remaining backspaces, if any.
 523         if bs_buf:
 524             result.extend(bs_buf)
 525
 526         if needquote:
 527             result.extend(bs_buf)
 528             result.append('"')
 529
 530     return ''.join(result)
 531
 532
 533 class Popen(object):
 534     def __init__(self, args, bufsize=0, executable=None,
 535                  stdin=None, stdout=None, stderr=None,
 536                  preexec_fn=None, close_fds=False, shell=False,
 537                  cwd=None, env=None, universal_newlines=False,
 538                  startupinfo=None, creationflags=0):
 539         """Create new Popen instance."""
 540         _cleanup()
 541
 542         self._child_created = False
 543         if not isinstance(bufsize, (int, long)):
 544             raise TypeError("bufsize must be an integer")
 545
 546         if mswindows:
 547             if preexec_fn is not None:
 548                 raise ValueError("preexec_fn is not supported on Windows "
 549                                  "platforms")
 550             if close_fds:
 551                 raise ValueError("close_fds is not supported on Windows "
 552                                  "platforms")
 553         else:
 554             # POSIX
 555             if startupinfo is not None:
 556                 raise ValueError("startupinfo is only supported on Windows "
 557                                  "platforms")
 558             if creationflags != 0:
 559                 raise ValueError("creationflags is only supported on Windows "
 560                                  "platforms")
 561
 562         self.stdin = None
 563         self.stdout = None
 564         self.stderr = None
 565         self.pid = None
 566         self.returncode = None
 567         self.universal_newlines = universal_newlines
 568
 569         # Input and output objects. The general principle is like
 570         # this:
 571         #
 572         # Parent                   Child
 573         # ------                   -----
 574         # p2cwrite   ---stdin--->  p2cread
 575         # c2pread    <--stdout---  c2pwrite
 576         # errread    <--stderr---  errwrite
 577         #
 578         # On POSIX, the child objects are file descriptors.  On
 579         # Windows, these are Windows file handles.  The parent objects
 580         # are file descriptors on both platforms.  The parent objects
 581         # are None when not using PIPEs. The child objects are None
 582         # when not redirecting.
 583
 584         (p2cread, p2cwrite,
 585          c2pread, c2pwrite,
 586          errread, errwrite) = self._get_handles(stdin, stdout, stderr)
 587
 588         self._execute_child(args, executable, preexec_fn, close_fds,
 589                             cwd, env, universal_newlines,
 590                             startupinfo, creationflags, shell,
 591                             p2cread, p2cwrite,
 592                             c2pread, c2pwrite,
 593                             errread, errwrite)
 594
 595         if p2cwrite:
 596             self.stdin = os.fdopen(p2cwrite, 'wb', bufsize)
 597         if c2pread:
 598             if universal_newlines:
 599                 self.stdout = os.fdopen(c2pread, 'rU', bufsize)
 600             else:
 601                 self.stdout = os.fdopen(c2pread, 'rb', bufsize)
 602         if errread:
 603             if universal_newlines:
 604                 self.stderr = os.fdopen(errread, 'rU', bufsize)
 605             else:
 606                 self.stderr = os.fdopen(errread, 'rb', bufsize)
 607
 608
 609     def _translate_newlines(self, data):
 610         data = data.replace("\r\n", "\n")
 611         data = data.replace("\r", "\n")
 612         return data
 613
 614
 615     def __del__(self):
 616         if not self._child_created:
 617             # We didn't get to successfully create a child process.
 618             return
 619         # In case the child hasn't been waited on, check if it's done.
 620         self.poll(_deadstate=sys.maxint)
 621         if self.returncode is None and _active is not None:
 622             # Child is still running, keep us alive until we can wait on it.
 623             _active.append(self)
 624
 625
 626     def communicate(self, input=None):
 627         """Interact with process: Send data to stdin.  Read data from
 628         stdout and stderr, until end-of-file is reached.  Wait for
 629         process to terminate.  The optional input argument should be a
 630         string to be sent to the child process, or None, if no data
 631         should be sent to the child.
 632
 633         communicate() returns a tuple (stdout, stderr)."""
 634
 635         # Optimization: If we are only using one pipe, or no pipe at
 636         # all, using select() or threads is unnecessary.
 637         if [self.stdin, self.stdout, self.stderr].count(None) >= 2:
 638             stdout = None
 639             stderr = None
 640             if self.stdin:
 641                 if input:
 642                     self.stdin.write(input)
 643                 self.stdin.close()
 644             elif self.stdout:
 645                 stdout = self.stdout.read()
 646             elif self.stderr:
 647                 stderr = self.stderr.read()
 648             self.wait()
 649             return (stdout, stderr)
 650
 651         return self._communicate(input)
 652
 653
 654     if mswindows:
 655         #
 656         # Windows methods
 657         #
 658         def _get_handles(self, stdin, stdout, stderr):
 659             """Construct and return tupel with IO objects:
 660             p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
 661             """
 662             if stdin is None and stdout is None and stderr is None:
 663                 return (None, None, None, None, None, None)
 664
 665             p2cread, p2cwrite = None, None
 666             c2pread, c2pwrite = None, None
 667             errread, errwrite = None, None
 668
 669             if stdin is None:
 670                 p2cread = GetStdHandle(STD_INPUT_HANDLE)
 671             elif stdin == PIPE:
 672                 p2cread, p2cwrite = CreatePipe(None, 0)
 673                 # Detach and turn into fd
 674                 p2cwrite = p2cwrite.Detach()
 675                 p2cwrite = msvcrt.open_osfhandle(p2cwrite, 0)
 676             elif isinstance(stdin, int):
 677                 p2cread = msvcrt.get_osfhandle(stdin)
 678             else:
 679                 # Assuming file-like object
 680                 p2cread = msvcrt.get_osfhandle(stdin.fileno())
 681             p2cread = self._make_inheritable(p2cread)
 682
 683             if stdout is None:
 684                 c2pwrite = GetStdHandle(STD_OUTPUT_HANDLE)
 685             elif stdout == PIPE:
 686                 c2pread, c2pwrite = CreatePipe(None, 0)
 687                 # Detach and turn into fd
 688                 c2pread = c2pread.Detach()
 689                 c2pread = msvcrt.open_osfhandle(c2pread, 0)
 690             elif isinstance(stdout, int):
 691                 c2pwrite = msvcrt.get_osfhandle(stdout)
 692             else:
 693                 # Assuming file-like object
 694                 c2pwrite = msvcrt.get_osfhandle(stdout.fileno())
 695             c2pwrite = self._make_inheritable(c2pwrite)
 696
 697             if stderr is None:
 698                 errwrite = GetStdHandle(STD_ERROR_HANDLE)
 699             elif stderr == PIPE:
 700                 errread, errwrite = CreatePipe(None, 0)
 701                 # Detach and turn into fd
 702                 errread = errread.Detach()
 703                 errread = msvcrt.open_osfhandle(errread, 0)
 704             elif stderr == STDOUT:
 705                 errwrite = c2pwrite
 706             elif isinstance(stderr, int):
 707                 errwrite = msvcrt.get_osfhandle(stderr)
 708             else:
 709                 # Assuming file-like object
 710                 errwrite = msvcrt.get_osfhandle(stderr.fileno())
 711             errwrite = self._make_inheritable(errwrite)
 712
 713             return (p2cread, p2cwrite,
 714                     c2pread, c2pwrite,
 715                     errread, errwrite)
 716
 717
 718         def _make_inheritable(self, handle):
 719             """Return a duplicate of handle, which is inheritable"""
 720             return DuplicateHandle(GetCurrentProcess(), handle,
 721                                    GetCurrentProcess(), 0, 1,
 722                                    DUPLICATE_SAME_ACCESS)
 723
 724
 725         def _find_w9xpopen(self):
 726             """Find and return absolut path to w9xpopen.exe"""
 727             w9xpopen = os.path.join(os.path.dirname(GetModuleFileName(0)),
 728                                     "w9xpopen.exe")
 729             if not os.path.exists(w9xpopen):
 730                 # Eeek - file-not-found - possibly an embedding
 731                 # situation - see if we can locate it in sys.exec_prefix
 732                 w9xpopen = os.path.join(os.path.dirname(sys.exec_prefix),
 733                                         "w9xpopen.exe")
 734                 if not os.path.exists(w9xpopen):
 735                     raise RuntimeError("Cannot locate w9xpopen.exe, which is "
 736                                        "needed for Popen to work with your "
 737                                        "shell or platform.")
 738             return w9xpopen
 739
 740
 741         def _execute_child(self, args, executable, preexec_fn, close_fds,
 742                            cwd, env, universal_newlines,
 743                            startupinfo, creationflags, shell,
 744                            p2cread, p2cwrite,
 745                            c2pread, c2pwrite,
 746                            errread, errwrite):
 747             """Execute program (MS Windows version)"""
 748
 749             if not isinstance(args, types.StringTypes):
 750                 args = list2cmdline(args)
 751
 752             # Process startup details
 753             if startupinfo is None:
 754                 startupinfo = STARTUPINFO()
 755             if None not in (p2cread, c2pwrite, errwrite):
 756                 startupinfo.dwFlags |= STARTF_USESTDHANDLES
 757                 startupinfo.hStdInput = p2cread
 758                 startupinfo.hStdOutput = c2pwrite
 759                 startupinfo.hStdError = errwrite
 760
 761             if shell:
 762                 startupinfo.dwFlags |= STARTF_USESHOWWINDOW
 763                 startupinfo.wShowWindow = SW_HIDE
 764                 comspec = os.environ.get("COMSPEC", "cmd.exe")
 765                 args = comspec + " /c " + args
 766                 if (GetVersion() >= 0x80000000L or
 767                         os.path.basename(comspec).lower() == "command.com"):
 768                     # Win9x, or using command.com on NT. We need to
 769                     # use the w9xpopen intermediate program. For more
 770                     # information, see KB Q150956
 771                     # (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp)
 772                     w9xpopen = self._find_w9xpopen()
 773                     args = '"%s" %s' % (w9xpopen, args)
 774                     # Not passing CREATE_NEW_CONSOLE has been known to
 775                     # cause random failures on win9x.  Specifically a
 776                     # dialog: "Your program accessed mem currently in
 777                     # use at xxx" and a hopeful warning about the
 778                     # stability of your system.  Cost is Ctrl+C wont
 779                     # kill children.
 780                     creationflags |= CREATE_NEW_CONSOLE
 781
 782             # Start the process
 783             try:
 784                 hp, ht, pid, tid = CreateProcess(executable, args,
 785                                          # no special security
 786                                          None, None,
 787                                          # must inherit handles to pass std
 788                                          # handles
 789                                          1,
 790                                          creationflags,
 791                                          env,
 792                                          cwd,
 793                                          startupinfo)
 794             except pywintypes.error, e:
 795                 # Translate pywintypes.error to WindowsError, which is
 796                 # a subclass of OSError.  FIXME: We should really
 797                 # translate errno using _sys_errlist (or simliar), but
 798                 # how can this be done from Python?
 799                 raise WindowsError(*e.args)
 800
 801             # Retain the process handle, but close the thread handle
 802             self._child_created = True
 803             self._handle = hp
 804             self.pid = pid
 805             ht.Close()
 806
 807             # Child is launched. Close the parent's copy of those pipe
 808             # handles that only the child should have open.  You need
 809             # to make sure that no handles to the write end of the
 810             # output pipe are maintained in this process or else the
 811             # pipe will not close when the child process exits and the
 812             # ReadFile will hang.
 813             if p2cread is not None:
 814                 p2cread.Close()
 815             if c2pwrite is not None:
 816                 c2pwrite.Close()
 817             if errwrite is not None:
 818                 errwrite.Close()
 819
 820
 821         def poll(self, _deadstate=None):
 822             """Check if child process has terminated.  Returns returncode
 823             attribute."""
 824             if self.returncode is None:
 825                 if WaitForSingleObject(self._handle, 0) == WAIT_OBJECT_0:
 826                     self.returncode = GetExitCodeProcess(self._handle)
 827             return self.returncode
 828
 829
 830         def wait(self):
 831             """Wait for child process to terminate.  Returns returncode
 832             attribute."""
 833             if self.returncode is None:
 834                 obj = WaitForSingleObject(self._handle, INFINITE)
 835                 self.returncode = GetExitCodeProcess(self._handle)
 836             return self.returncode
 837
 838
 839         def _readerthread(self, fh, buffer):
 840             buffer.append(fh.read())
 841
 842
 843         def _communicate(self, input):
 844             stdout = None # Return
 845             stderr = None # Return
 846
 847             if self.stdout:
 848                 stdout = []
 849                 stdout_thread = threading.Thread(target=self._readerthread,
 850                                                  args=(self.stdout, stdout))
 851                 stdout_thread.setDaemon(True)
 852                 stdout_thread.start()
 853             if self.stderr:
 854                 stderr = []
 855                 stderr_thread = threading.Thread(target=self._readerthread,
 856                                                  args=(self.stderr, stderr))
 857                 stderr_thread.setDaemon(True)
 858                 stderr_thread.start()
 859
 860             if self.stdin:
 861                 if input is not None:
 862                     self.stdin.write(input)
 863                 self.stdin.close()
 864
 865             if self.stdout:
 866                 stdout_thread.join()
 867             if self.stderr:
 868                 stderr_thread.join()
 869
 870             # All data exchanged.  Translate lists into strings.
 871             if stdout is not None:
 872                 stdout = stdout[0]
 873             if stderr is not None:
 874                 stderr = stderr[0]
 875
 876             # Translate newlines, if requested.  We cannot let the file
 877             # object do the translation: It is based on stdio, which is
 878             # impossible to combine with select (unless forcing no
 879             # buffering).
 880             if self.universal_newlines and hasattr(file, 'newlines'):
 881                 if stdout:
 882                     stdout = self._translate_newlines(stdout)
 883                 if stderr:
 884                     stderr = self._translate_newlines(stderr)
 885
 886             self.wait()
 887             return (stdout, stderr)
 888
 889     else:
 890         #
 891         # POSIX methods
 892         #
 893         def _get_handles(self, stdin, stdout, stderr):
 894             """Construct and return tupel with IO objects:
 895             p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
 896             """
 897             p2cread, p2cwrite = None, None
 898             c2pread, c2pwrite = None, None
 899             errread, errwrite = None, None
 900
 901             if stdin is None:
 902                 pass
 903             elif stdin == PIPE:
 904                 p2cread, p2cwrite = os.pipe()
 905             elif isinstance(stdin, int):
 906                 p2cread = stdin
 907             else:
 908                 # Assuming file-like object
 909                 p2cread = stdin.fileno()
 910
 911             if stdout is None:
 912                 pass
 913             elif stdout == PIPE:
 914                 c2pread, c2pwrite = os.pipe()
 915             elif isinstance(stdout, int):
 916                 c2pwrite = stdout
 917             else:
 918                 # Assuming file-like object
 919                 c2pwrite = stdout.fileno()
 920
 921             if stderr is None:
 922                 pass
 923             elif stderr == PIPE:
 924                 errread, errwrite = os.pipe()
 925             elif stderr == STDOUT:
 926                 errwrite = c2pwrite
 927             elif isinstance(stderr, int):
 928                 errwrite = stderr
 929             else:
 930                 # Assuming file-like object
 931                 errwrite = stderr.fileno()
 932
 933             return (p2cread, p2cwrite,
 934                     c2pread, c2pwrite,
 935                     errread, errwrite)
 936
 937
 938         def _set_cloexec_flag(self, fd):
 939             try:
 940                 cloexec_flag = fcntl.FD_CLOEXEC
 941             except AttributeError:
 942                 cloexec_flag = 1
 943
 944             old = fcntl.fcntl(fd, fcntl.F_GETFD)
 945             fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag)
 946
 947
 948         def _close_fds(self, but):
 949             for i in xrange(3, MAXFD):
 950                 if i == but:
 951                     continue
 952                 try:
 953                     os.close(i)
 954                 except:
 955                     pass
 956
 957
 958         def _execute_child(self, args, executable, preexec_fn, close_fds,
 959                            cwd, env, universal_newlines,
 960                            startupinfo, creationflags, shell,
 961                            p2cread, p2cwrite,
 962                            c2pread, c2pwrite,
 963                            errread, errwrite):
 964             """Execute program (POSIX version)"""
 965
 966             if isinstance(args, types.StringTypes):
 967                 args = [args]
 968
 969             if shell:
 970                 args = ["/bin/sh", "-c"] + args
 971
 972             if executable is None:
 973                 executable = args[0]
 974
 975             # For transferring possible exec failure from child to parent
 976             # The first char specifies the exception type: 0 means
 977             # OSError, 1 means some other error.
 978             errpipe_read, errpipe_write = os.pipe()
 979             self._set_cloexec_flag(errpipe_write)
 980
 981             self.pid = os.fork()
 982             self._child_created = True
 983             if self.pid == 0:
 984                 # Child
 985                 try:
 986                     # Close parent's pipe ends
 987                     if p2cwrite:
 988                         os.close(p2cwrite)
 989                     if c2pread:
 990                         os.close(c2pread)
 991                     if errread:
 992                         os.close(errread)
 993                     os.close(errpipe_read)
 994
 995                     # Dup fds for child
 996                     if p2cread:
 997                         os.dup2(p2cread, 0)
 998                     if c2pwrite:
 999                         os.dup2(c2pwrite, 1)
1000                     if errwrite:
1001                         os.dup2(errwrite, 2)
1002
1003                     # Close pipe fds.  Make sure we don't close the same
1004                     # fd more than once, or standard fds.
1005                     if p2cread:
1006                         os.close(p2cread)
1007                     if c2pwrite and c2pwrite not in (p2cread,):
1008                         os.close(c2pwrite)
1009                     if errwrite and errwrite not in (p2cread, c2pwrite):
1010                         os.close(errwrite)
1011
1012                     # Close all other fds, if asked for
1013                     if close_fds:
1014                         self._close_fds(but=errpipe_write)
1015
1016                     if cwd is not None:
1017                         os.chdir(cwd)
1018
1019                     if preexec_fn:
1020                         apply(preexec_fn)
1021
1022                     if env is None:
1023                         os.execvp(executable, args)
1024                     else:
1025                         os.execvpe(executable, args, env)
1026
1027                 except:
1028                     exc_type, exc_value, tb = sys.exc_info()
1029                     # Save the traceback and attach it to the exception object
1030                     exc_lines = traceback.format_exception(exc_type,
1031                                                            exc_value,
1032                                                            tb)
1033                     exc_value.child_traceback = ''.join(exc_lines)
1034                     os.write(errpipe_write, pickle.dumps(exc_value))
1035
1036                 # This exitcode won't be reported to applications, so it
1037                 # really doesn't matter what we return.
1038                 os._exit(255)
1039
1040             # Parent
1041             os.close(errpipe_write)
1042             if p2cread and p2cwrite:
1043                 os.close(p2cread)
1044             if c2pwrite and c2pread:
1045                 os.close(c2pwrite)
1046             if errwrite and errread:
1047                 os.close(errwrite)
1048
1049             # Wait for exec to fail or succeed; possibly raising exception
1050             data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB
1051             os.close(errpipe_read)
1052             if data != "":
1053                 os.waitpid(self.pid, 0)
1054                 child_exception = pickle.loads(data)
1055                 raise child_exception
1056
1057
1058         def _handle_exitstatus(self, sts):
1059             if os.WIFSIGNALED(sts):
1060                 self.returncode = -os.WTERMSIG(sts)
1061             elif os.WIFEXITED(sts):
1062                 self.returncode = os.WEXITSTATUS(sts)
1063             else:
1064                 # Should never happen
1065                 raise RuntimeError("Unknown child exit status!")
1066
1067
1068         def poll(self, _deadstate=None):
1069             """Check if child process has terminated.  Returns returncode
1070             attribute."""
1071             if self.returncode is None:
1072                 try:
1073                     pid, sts = os.waitpid(self.pid, os.WNOHANG)
1074                     if pid == self.pid:
1075                         self._handle_exitstatus(sts)
1076                 except os.error:
1077                     if _deadstate is not None:
1078                         self.returncode = _deadstate
1079             return self.returncode
1080
1081
1082         def wait(self):
1083             """Wait for child process to terminate.  Returns returncode
1084             attribute."""
1085             if self.returncode is None:
1086                 pid, sts = os.waitpid(self.pid, 0)
1087                 self._handle_exitstatus(sts)
1088             return self.returncode
1089
1090
1091         def _communicate(self, input):
1092             read_set = []
1093             write_set = []
1094             stdout = None # Return
1095             stderr = None # Return
1096
1097             if self.stdin:
1098                 # Flush stdio buffer.  This might block, if the user has
1099                 # been writing to .stdin in an uncontrolled fashion.
1100                 self.stdin.flush()
1101                 if input:
1102                     write_set.append(self.stdin)
1103                 else:
1104                     self.stdin.close()
1105             if self.stdout:
1106                 read_set.append(self.stdout)
1107                 stdout = []
1108             if self.stderr:
1109                 read_set.append(self.stderr)
1110                 stderr = []
1111
1112             while read_set or write_set:
1113                 rlist, wlist, xlist = select.select(read_set, write_set, [])
1114
1115                 if self.stdin in wlist:
1116                     # When select has indicated that the file is writable,
1117                     # we can write up to PIPE_BUF bytes without risk
1118                     # blocking.  POSIX defines PIPE_BUF >= 512
1119                     bytes_written = os.write(self.stdin.fileno(), input[:512])
1120                     input = input[bytes_written:]
1121                     if not input:
1122                         self.stdin.close()
1123                         write_set.remove(self.stdin)
1124
1125                 if self.stdout in rlist:
1126                     data = os.read(self.stdout.fileno(), 1024)
1127                     if data == "":
1128                         self.stdout.close()
1129                         read_set.remove(self.stdout)
1130                     stdout.append(data)
1131
1132                 if self.stderr in rlist:
1133                     data = os.read(self.stderr.fileno(), 1024)
1134                     if data == "":
1135                         self.stderr.close()
1136                         read_set.remove(self.stderr)
1137                     stderr.append(data)
1138
1139             # All data exchanged.  Translate lists into strings.
1140             if stdout is not None:
1141                 stdout = ''.join(stdout)
1142             if stderr is not None:
1143                 stderr = ''.join(stderr)
1144
1145             # Translate newlines, if requested.  We cannot let the file
1146             # object do the translation: It is based on stdio, which is
1147             # impossible to combine with select (unless forcing no
1148             # buffering).
1149             if self.universal_newlines and hasattr(file, 'newlines'):
1150                 if stdout:
1151                     stdout = self._translate_newlines(stdout)
1152                 if stderr:
1153                     stderr = self._translate_newlines(stderr)
1154
1155             self.wait()
1156             return (stdout, stderr)
1157
1158
1159 def _demo_posix():
1160     #
1161     # Example 1: Simple redirection: Get process list
1162     #
1163     plist = Popen(["ps"], stdout=PIPE).communicate()[0]
1164     print "Process list:"
1165     print plist
1166
1167     #
1168     # Example 2: Change uid before executing child
1169     #
1170     if os.getuid() == 0:
1171         p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
1172         p.wait()
1173
1174     #
1175     # Example 3: Connecting several subprocesses
1176     #
1177     print "Looking for 'hda'..."
1178     p1 = Popen(["dmesg"], stdout=PIPE)
1179     p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
1180     print repr(p2.communicate()[0])
1181
1182     #
1183     # Example 4: Catch execution error
1184     #
1185     print
1186     print "Trying a weird file..."
1187     try:
1188         print Popen(["/this/path/does/not/exist"]).communicate()
1189     except OSError, e:
1190         if e.errno == errno.ENOENT:
1191             print "The file didn't exist.  I thought so..."
1192             print "Child traceback:"
1193             print e.child_traceback
1194         else:
1195             print "Error", e.errno
1196     else:
1197         print >>sys.stderr, "Gosh.  No error."
1198
1199
1200 def _demo_windows():
1201     #
1202     # Example 1: Connecting several subprocesses
1203     #
1204     print "Looking for 'PROMPT' in set output..."
1205     p1 = Popen("set", stdout=PIPE, shell=True)
1206     p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
1207     print repr(p2.communicate()[0])
1208
1209     #
1210     # Example 2: Simple execution of program
1211     #
1212     print "Executing calc..."
1213     p = Popen("calc")
1214     p.wait()
1215
1216
1217 if __name__ == "__main__":
1218     if mswindows:
1219         _demo_windows()
1220     else:
1221         _demo_posix()