subprocess.py

Wxpython Implemented on Windows CE, Source code

            stdout = None # Return
            stderr = None # Return

            if self.stdout:
                stdout = []
                stdout_thread = threading.Thread(target=self._readerthread,
                                                 args=(self.stdout, stdout))
                stdout_thread.setDaemon(True)
                stdout_thread.start()
            if self.stderr:
                stderr = []
                stderr_thread = threading.Thread(target=self._readerthread,
                                                 args=(self.stderr, stderr))
                stderr_thread.setDaemon(True)
                stderr_thread.start()

            if self.stdin:
                if input != 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 != None:
                stdout = stdout[0]
            if stderr != None:
                stderr = stderr[0]

            # Translate newlines, if requested.  We cannot let the file
            # object do the translation: It is based on stdio, which is
            # impossible to combine with select (unless forcing no
            # buffering).
            if self.universal_newlines and hasattr(open, 'newlines'):
                if stdout:
                    stdout = self._translate_newlines(stdout)
                if stderr:
                    stderr = self._translate_newlines(stderr)

            self.wait()
            return (stdout, stderr)

    else:
        #
        # POSIX methods
        #
        def _get_handles(self, stdin, stdout, stderr):
            """Construct and return tupel with IO objects:
            p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
            """
            p2cread, p2cwrite = None, None
            c2pread, c2pwrite = None, None
            errread, errwrite = None, None

            if stdin == None:
                pass
            elif stdin == PIPE:
                p2cread, p2cwrite = os.pipe()
            elif type(stdin) == types.IntType:
                p2cread = stdin
            else:
                # Assuming file-like object
                p2cread = stdin.fileno()

            if stdout == None:
                pass
            elif stdout == PIPE:
                c2pread, c2pwrite = os.pipe()
            elif type(stdout) == types.IntType:
                c2pwrite = stdout
            else:
                # Assuming file-like object
                c2pwrite = stdout.fileno()

            if stderr == None:
                pass
            elif stderr == PIPE:
                errread, errwrite = os.pipe()
            elif stderr == STDOUT:
                errwrite = c2pwrite
            elif type(stderr) == types.IntType:
                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):
            for i in range(3, MAXFD):
                if i == but:
                    continue
                try:
                    os.close(i)
                except:
                    pass


        def _execute_child(self, args, executable, preexec_fn, close_fds,
                           cwd, env, universal_newlines,
                           startupinfo, creationflags, shell,
                           p2cread, p2cwrite,
                           c2pread, c2pwrite,
                           errread, errwrite):
            """Execute program (POSIX version)"""

            if isinstance(args, types.StringTypes):
                args = [args]

            if shell:
                args = ["/bin/sh", "-c"] + args

            if executable == None:
                executable = args[0]

            # For transferring possible exec failure from child to parent
            # The first char specifies the exception type: 0 means
            # OSError, 1 means some other error.
            errpipe_read, errpipe_write = os.pipe()
            self._set_cloexec_flag(errpipe_write)

            self.pid = os.fork()
            if self.pid == 0:
                # Child
                try:
                    # Close parent's pipe ends
                    if p2cwrite:
                        os.close(p2cwrite)
                    if c2pread:
                        os.close(c2pread)
                    if errread:
                        os.close(errread)
                    os.close(errpipe_read)

                    # Dup fds for child
                    if p2cread:
                        os.dup2(p2cread, 0)
                    if c2pwrite:
                        os.dup2(c2pwrite, 1)
                    if errwrite:
                        os.dup2(errwrite, 2)

                    # Close pipe fds.  Make sure we doesn't close the same
                    # fd more than once.
                    if p2cread:
                        os.close(p2cread)
                    if c2pwrite and c2pwrite not in (p2cread,):
                        os.close(c2pwrite)
                    if errwrite and errwrite not in (p2cread, c2pwrite):
                        os.close(errwrite)

                    # Close all other fds, if asked for
                    if close_fds:
                        self._close_fds(but=errpipe_write)

                    if cwd != None:
                        os.chdir(cwd)

                    if preexec_fn:
                        apply(preexec_fn)

                    if env == None:
                        os.execvp(executable, args)
                    else:
                        os.execvpe(executable, args, env)

                except:
                    exc_type, exc_value, tb = sys.exc_info()
                    # Save the traceback and attach it to the exception object
                    exc_lines = traceback.format_exception(exc_type,
                                                           exc_value,
                                                           tb)
                    exc_value.child_traceback = ''.join(exc_lines)
                    os.write(errpipe_write, pickle.dumps(exc_value))

                # This exitcode won't be reported to applications, so it
                # really doesn't matter what we return.
                os._exit(255)

            # Parent
            os.close(errpipe_write)
            if p2cread and p2cwrite:
                os.close(p2cread)
            if c2pwrite and c2pread:
                os.close(c2pwrite)
            if errwrite and errread:
                os.close(errwrite)

            # Wait for exec to fail or succeed; possibly raising exception
            data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB
            os.close(errpipe_read)
            if data != "":
                child_exception = pickle.loads(data)
                raise child_exception


        def _handle_exitstatus(self, sts):
            if os.WIFSIGNALED(sts):
                self.returncode = -os.WTERMSIG(sts)
            elif os.WIFEXITED(sts):
                self.returncode = os.WEXITSTATUS(sts)
            else:
                # Should never happen
                raise RuntimeError("Unknown child exit status!")

            _active.remove(self)


        def poll(self):
            """Check if child process has terminated.  Returns returncode
            attribute."""
            if self.returncode == None:
                try:
                    pid, sts = os.waitpid(self.pid, os.WNOHANG)
                    if pid == self.pid:
                        self._handle_exitstatus(sts)
                except os.error:
                    pass
            return self.returncode


        def wait(self):
            """Wait for child process to terminate.  Returns returncode
            attribute."""
            if self.returncode == None:
                pid, sts = os.waitpid(self.pid, 0)
                self._handle_exitstatus(sts)
            return self.returncode


        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)."""
            read_set = []
            write_set = []
            stdout = None # Return
            stderr = None # Return

            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 input:
                    write_set.append(self.stdin)
                else:
                    self.stdin.close()
            if self.stdout:
                read_set.append(self.stdout)
                stdout = []
            if self.stderr:
                read_set.append(self.stderr)
                stderr = []

            while read_set or write_set:
                rlist, wlist, xlist = select.select(read_set, write_set, [])

                if self.stdin in wlist:
                    # When select has indicated that the file is writable,
                    # we can write up to PIPE_BUF bytes without risk
                    # blocking.  POSIX defines PIPE_BUF >= 512
                    bytes_written = os.write(self.stdin.fileno(), input[:512])
                    input = input[bytes_written:]
                    if not input:
                        self.stdin.close()
                        write_set.remove(self.stdin)

                if self.stdout in rlist:
                    data = os.read(self.stdout.fileno(), 1024)
                    if 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 data == "":
                        self.stderr.close()
                        read_set.remove(self.stderr)
                    stderr.append(data)

            # All data exchanged.  Translate lists into strings.
            if stdout != None:
                stdout = ''.join(stdout)
            if stderr != None:
                stderr = ''.join(stderr)

            # Translate newlines, if requested.  We cannot let the file
            # object do the translation: It is based on stdio, which is
            # impossible to combine with select (unless forcing no
            # buffering).
            if self.universal_newlines and hasattr(open, 'newlines'):
                if stdout:
                    stdout = self._translate_newlines(stdout)
                if stderr:
                    stderr = self._translate_newlines(stderr)

            self.wait()
            return (stdout, stderr)


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, 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 >>sys.stderr, "Gosh.  No error."


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()