This adds a new library on top of subprocess which permits access to the subprocess output as it is being generated. We can therefore give the illusion that a process is running independently, but still monitor its output so that we know what is going on.
It is possible to display output on a terminal as it is generated (a little like tee). The supplied output function is called with all stdout/stderr data as it arrives.
Signed-off-by: Simon Glass sjg@chromium.org --- Changes in v2: None
tools/patman/cros_subprocess.py | 397 +++++++++++++++++++++++++++++++++++++++ 1 files changed, 397 insertions(+), 0 deletions(-) create mode 100644 tools/patman/cros_subprocess.py
diff --git a/tools/patman/cros_subprocess.py b/tools/patman/cros_subprocess.py new file mode 100644 index 0000000..0fc4a06 --- /dev/null +++ b/tools/patman/cros_subprocess.py @@ -0,0 +1,397 @@ +# Copyright (c) 2012 The Chromium OS Authors. +# Use of this source code is governed by a BSD-style license that can be +# found in the LICENSE file. +# +# Copyright (c) 2003-2005 by Peter Astrand astrand@lysator.liu.se +# Licensed to PSF under a Contributor Agreement. +# See http://www.python.org/2.4/license for licensing details. + +"""Subprocress execution + +This module holds a subclass of subprocess.Popen with our own required +features, mainly that we get access to the subprocess output while it +is running rather than just at the end. This makes it easiler to show +progress information and filter output in real time. +""" + +import errno +import os +import pty +import select +import subprocess +import sys +import unittest + + +# Import these here so the caller does not need to import subprocess also. +PIPE = subprocess.PIPE +STDOUT = subprocess.STDOUT +PIPE_PTY = -3 # Pipe output through a pty +stay_alive = True + + +class Popen(subprocess.Popen): + """Like subprocess.Popen with ptys and incremental output + + This class deals with running a child process and filtering its output on + both stdout and stderr while it is running. We do this so we can monitor + progress, and possibly relay the output to the user if requested. + + The class is similar to subprocess.Popen, the equivalent is something like: + + Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE) + + But this class has many fewer features, and two enhancement: + + 1. Rather than getting the output data only at the end, this class sends it + to a provided operation as it arrives. + 2. We use pseudo terminals so that the child will hopefully flush its output + to us as soon as it is produced, rather than waiting for the end of a + line. + + Use CommunicateFilter() to handle output from the subprocess. + + """ + + def __init__(self, args, stdin=None, stdout=PIPE_PTY, stderr=PIPE_PTY, + shell=False, cwd=None, env=None, **kwargs): + """Cut-down constructor + + Args: + args: Program and arguments for subprocess to execute. + stdin: See subprocess.Popen() + stdout: See subprocess.Popen(), except that we support the sentinel + value of cros_subprocess.PIPE_PTY. + stderr: See subprocess.Popen(), except that we support the sentinel + value of cros_subprocess.PIPE_PTY. + shell: See subprocess.Popen() + cwd: Working directory to change to for subprocess, or None if none. + env: Environment to use for this subprocess, or None to inherit parent. + kwargs: No other arguments are supported at the moment. Passing other + arguments will cause a ValueError to be raised. + """ + stdout_pty = None + stderr_pty = None + + if stdout == PIPE_PTY: + stdout_pty = pty.openpty() + stdout = os.fdopen(stdout_pty[1]) + if stderr == PIPE_PTY: + stderr_pty = pty.openpty() + stderr = os.fdopen(stderr_pty[1]) + + super(Popen, self).__init__(args, stdin=stdin, + stdout=stdout, stderr=stderr, shell=shell, cwd=cwd, env=env, + **kwargs) + + # If we're on a PTY, we passed the slave half of the PTY to the subprocess. + # We want to use the master half on our end from now on. Setting this here + # does make some assumptions about the implementation of subprocess, but + # those assumptions are pretty minor. + + # Note that if stderr is STDOUT, then self.stderr will be set to None by + # this constructor. + if stdout_pty is not None: + self.stdout = os.fdopen(stdout_pty[0]) + if stderr_pty is not None: + self.stderr = os.fdopen(stderr_pty[0]) + + # Insist that unit tests exist for other arguments we don't support. + if kwargs: + raise ValueError("Unit tests do not test extra args - please add tests") + + def CommunicateFilter(self, output): + """Interact with process: Read data from stdout and stderr. + + This method runs until end-of-file is reached, then waits for the + subprocess to terminate. + + The output function is sent all output from the subprocess and must be + defined like this: + + def Output([self,] stream, data) + Args: + stream: the stream the output was received on, which will be + sys.stdout or sys.stderr. + data: a string containing the data + + Note: The data read is buffered in memory, so do not use this + method if the data size is large or unlimited. + + Args: + output: Function to call with each fragment of output. + + Returns: + A tuple (stdout, stderr, combined) which is the data received on + stdout, stderr and the combined data (interleaved stdout and stderr). + + Note that the interleaved output will only be sensible if you have + set both stdout and stderr to PIPE or PIPE_PTY. Even then it depends on + the timing of the output in the subprocess. If a subprocess flips + between stdout and stderr quickly in succession, by the time we come to + read the output from each we may see several lines in each, and will read + all the stdout lines, then all the stderr lines. So the interleaving + may not be correct. In this case you might want to pass + stderr=cros_subprocess.STDOUT to the constructor. + + This feature is still useful for subprocesses where stderr is + rarely used and indicates an error. + + Note also that if you set stderr to STDOUT, then stderr will be empty + and the combined output will just be the same as stdout. + """ + + 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 and self.stderr != self.stdout: + read_set.append(self.stderr) + stderr = [] + combined = [] + + input_offset = 0 + while read_set or write_set: + try: + rlist, wlist, _ = select.select(read_set, write_set, [], 0.2) + except select.error, e: + if e.args[0] == errno.EINTR: + continue + raise + + if not stay_alive: + self.terminate() + + 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 + chunk = input[input_offset : input_offset + 512] + bytes_written = os.write(self.stdin.fileno(), chunk) + input_offset += bytes_written + if input_offset >= len(input): + self.stdin.close() + write_set.remove(self.stdin) + + if self.stdout in rlist: + data = "" + # We will get an error on read if the pty is closed + try: + data = os.read(self.stdout.fileno(), 1024) + except OSError: + pass + if data == "": + self.stdout.close() + read_set.remove(self.stdout) + else: + stdout.append(data) + combined.append(data) + if output: + output(sys.stdout, data) + if self.stderr in rlist: + data = "" + # We will get an error on read if the pty is closed + try: + data = os.read(self.stderr.fileno(), 1024) + except OSError: + pass + if data == "": + self.stderr.close() + read_set.remove(self.stderr) + else: + stderr.append(data) + combined.append(data) + if output: + output(sys.stderr, data) + + # All data exchanged. Translate lists into strings. + if stdout is not None: + stdout = ''.join(stdout) + else: + stdout = '' + if stderr is not None: + stderr = ''.join(stderr) + else: + stderr = '' + combined = ''.join(combined) + + # 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(file, 'newlines'): + if stdout: + stdout = self._translate_newlines(stdout) + if stderr: + stderr = self._translate_newlines(stderr) + + self.wait() + return (stdout, stderr, combined) + + +# Just being a unittest.TestCase gives us 14 public methods. Unless we +# disable this, we can only have 6 tests in a TestCase. That's not enough. +# +# pylint: disable=R0904 + +class TestSubprocess(unittest.TestCase): + """Our simple unit test for this module""" + + class MyOperation: + """Provides a operation that we can pass to Popen""" + def __init__(self, input_to_send=None): + """Constructor to set up the operation and possible input. + + Args: + input_to_send: a text string to send when we first get input. We will + add \r\n to the string. + """ + self.stdout_data = '' + self.stderr_data = '' + self.combined_data = '' + self.stdin_pipe = None + self._input_to_send = input_to_send + if input_to_send: + pipe = os.pipe() + self.stdin_read_pipe = pipe[0] + self._stdin_write_pipe = os.fdopen(pipe[1], 'w') + + def Output(self, stream, data): + """Output handler for Popen. Stores the data for later comparison""" + if stream == sys.stdout: + self.stdout_data += data + if stream == sys.stderr: + self.stderr_data += data + self.combined_data += data + + # Output the input string if we have one. + if self._input_to_send: + self._stdin_write_pipe.write(self._input_to_send + '\r\n') + self._stdin_write_pipe.flush() + + def _BasicCheck(self, plist, oper): + """Basic checks that the output looks sane.""" + self.assertEqual(plist[0], oper.stdout_data) + self.assertEqual(plist[1], oper.stderr_data) + self.assertEqual(plist[2], oper.combined_data) + + # The total length of stdout and stderr should equal the combined length + self.assertEqual(len(plist[0]) + len(plist[1]), len(plist[2])) + + def test_simple(self): + """Simple redirection: Get process list""" + oper = TestSubprocess.MyOperation() + plist = Popen(['ps']).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + + def test_stderr(self): + """Check stdout and stderr""" + oper = TestSubprocess.MyOperation() + cmd = 'echo fred >/dev/stderr && false || echo bad' + plist = Popen([cmd], shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], 'bad\r\n') + self.assertEqual(plist [1], 'fred\r\n') + + def test_shell(self): + """Check with and without shell works""" + oper = TestSubprocess.MyOperation() + cmd = 'echo test >/dev/stderr' + self.assertRaises(OSError, Popen, [cmd], shell=False) + plist = Popen([cmd], shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(len(plist [0]), 0) + self.assertEqual(plist [1], 'test\r\n') + + def test_list_args(self): + """Check with and without shell works using list arguments""" + oper = TestSubprocess.MyOperation() + cmd = ['echo', 'test', '>/dev/stderr'] + plist = Popen(cmd, shell=False).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], ' '.join(cmd[1:]) + '\r\n') + self.assertEqual(len(plist [1]), 0) + + oper = TestSubprocess.MyOperation() + + # this should be interpreted as 'echo' with the other args dropped + cmd = ['echo', 'test', '>/dev/stderr'] + plist = Popen(cmd, shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], '\r\n') + + def test_cwd(self): + """Check we can change directory""" + for shell in (False, True): + oper = TestSubprocess.MyOperation() + plist = Popen('pwd', shell=shell, cwd='/tmp').CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], '/tmp\r\n') + + def test_env(self): + """Check we can change environment""" + for add in (False, True): + oper = TestSubprocess.MyOperation() + env = os.environ + if add: + env ['FRED'] = 'fred' + cmd = 'echo $FRED' + plist = Popen(cmd, shell=True, env=env).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], add and 'fred\r\n' or '\r\n') + + def test_extra_args(self): + """Check we can't add extra arguments""" + self.assertRaises(ValueError, Popen, 'true', close_fds=False) + + def test_basic_input(self): + """Check that incremental input works + + We set up a subprocess which will prompt for name. When we see this prompt + we send the name as input to the process. It should then print the name + properly to stdout. + """ + oper = TestSubprocess.MyOperation('Flash') + prompt = 'What is your name?: ' + cmd = 'echo -n "%s"; read name; echo Hello $name' % prompt + plist = Popen([cmd], stdin=oper.stdin_read_pipe, + shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(len(plist [1]), 0) + self.assertEqual(plist [0], prompt + 'Hello Flash\r\r\n') + + def test_isatty(self): + """Check that ptys appear as terminals to the subprocess""" + oper = TestSubprocess.MyOperation() + cmd = ('if [ -t %d ]; then echo "terminal %d" >&%d; ' + 'else echo "not %d" >&%d; fi;') + both_cmds = '' + for fd in (1, 2): + both_cmds += cmd % (fd, fd, fd, fd, fd) + plist = Popen(both_cmds, shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], 'terminal 1\r\n') + self.assertEqual(plist [1], 'terminal 2\r\n') + + # Now try with PIPE and make sure it is not a terminal + oper = TestSubprocess.MyOperation() + plist = Popen(both_cmds, stdout=subprocess.PIPE, stderr=subprocess.PIPE, + shell=True).CommunicateFilter(oper.Output) + self._BasicCheck(plist, oper) + self.assertEqual(plist [0], 'not 1\n') + self.assertEqual(plist [1], 'not 2\n') + +if __name__ == '__main__': + unittest.main()