Minor robustness/speed improvements to process handling

IPython/utils/_process_posix.py

@@ -1,192 +1,194 b''
 """Posix-specific implementation of process utilities.
 
 This file is only meant to be imported by process.py, not by end-users.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 # Stdlib
 import subprocess as sp
 import sys
 
 # Third-party
 # We ship our own copy of pexpect (it's a single file) to minimize dependencies
 # for users, but it's only used if we don't find the system copy.
 try:
     import pexpect
 except ImportError:
     from IPython.external import pexpect
 
 # Our own
 from .autoattr import auto_attr
 from ._process_common import getoutput
 
 #-----------------------------------------------------------------------------
 # Function definitions
 #-----------------------------------------------------------------------------
 
 def _find_cmd(cmd):
     """Find the full path to a command using which."""
 
     return sp.Popen(['/usr/bin/env', 'which', cmd],
                     stdout=sp.PIPE).communicate()[0]
 
 
 class ProcessHandler(object):
     """Execute subprocesses under the control of pexpect.
     """
     # Timeout in seconds to wait on each reading of the subprocess' output.
     # This should not be set too low to avoid cpu overusage from our side,
     # since we read in a loop whose period is controlled by this timeout.
     read_timeout = 0.05
 
     # Timeout to give a process if we receive SIGINT, between sending the
     # SIGINT to the process and forcefully terminating it.
     terminate_timeout = 0.2
 
     # File object where stdout and stderr of the subprocess will be written
     logfile = None
 
     # Shell to call for subprocesses to execute
     sh = None
 
     @auto_attr
     def sh(self):
         sh = pexpect.which('sh')
         if sh is None:
             raise OSError('"sh" shell not found')
         return sh
 
     def __init__(self, logfile=None, read_timeout=None, terminate_timeout=None):
         """Arguments are used for pexpect calls."""
         self.read_timeout = (ProcessHandler.read_timeout if read_timeout is
                              None else read_timeout)
         self.terminate_timeout = (ProcessHandler.terminate_timeout if
                                   terminate_timeout is None else
                                   terminate_timeout)
         self.logfile = sys.stdout if logfile is None else logfile
 
     def getoutput(self, cmd):
         """Run a command and return its stdout/stderr as a string.
 
         Parameters
         ----------
         cmd : str
           A command to be executed in the system shell.
 
         Returns
         -------
         output : str
           A string containing the combination of stdout and stderr from the
         subprocess, in whatever order the subprocess originally wrote to its
         file descriptors (so the order of the information in this string is the
         correct order as would be seen if running the command in a terminal).
         """
         pcmd = self._make_cmd(cmd)
         try:
             return pexpect.run(pcmd).replace('\r\n', '\n')
         except KeyboardInterrupt:
             print('^C', file=sys.stderr, end='')
 
     def getoutput_pexpect(self, cmd):
         """Run a command and return its stdout/stderr as a string.
 
         Parameters
         ----------
         cmd : str
           A command to be executed in the system shell.
 
         Returns
         -------
         output : str
           A string containing the combination of stdout and stderr from the
         subprocess, in whatever order the subprocess originally wrote to its
         file descriptors (so the order of the information in this string is the
         correct order as would be seen if running the command in a terminal).
         """
         pcmd = self._make_cmd(cmd)
         try:
             return pexpect.run(pcmd).replace('\r\n', '\n')
         except KeyboardInterrupt:
             print('^C', file=sys.stderr, end='')
 
     def system(self, cmd):
         """Execute a command in a subshell.
 
         Parameters
         ----------
         cmd : str
           A command to be executed in the system shell.
 
         Returns
         -------
         None : we explicitly do NOT return the subprocess status code, as this
         utility is meant to be used extensively in IPython, where any return
         value would trigger :func:`sys.displayhook` calls.
         """
         pcmd = self._make_cmd(cmd)
         # Patterns to match on the output, for pexpect.  We read input and
         # allow either a short timeout or EOF
         patterns = [pexpect.TIMEOUT, pexpect.EOF]
         # the index of the EOF pattern in the list.
         EOF_index = 1  # Fix this index if you change the list!!
         # The size of the output stored so far in the process output buffer.
         # Since pexpect only appends to this buffer, each time we print we
         # record how far we've printed, so that next time we only print *new*
         # content from the buffer.
         out_size = 0
         try:
             # Since we're not really searching the buffer for text patterns, we
             # can set pexpect's search window to be tiny and it won't matter.
             # We only search for the 'patterns' timeout or EOF, which aren't in
             # the text itself.
-            child = pexpect.spawn(pcmd, searchwindowsize=1)
+            #child = pexpect.spawn(pcmd, searchwindowsize=1)
+            child = pexpect.spawn(pcmd)
             flush = sys.stdout.flush
             while True:
                 # res is the index of the pattern that caused the match, so we
                 # know whether we've finished (if we matched EOF) or not
                 res_idx = child.expect_list(patterns, self.read_timeout)
                 print(child.before[out_size:], end='')
                 flush()
-                # Update the pointer to what we've already printed
-                out_size = len(child.before)
                 if res_idx==EOF_index:
                     break
+                # Update the pointer to what we've already printed
+                out_size = len(child.before)
         except KeyboardInterrupt:
             # We need to send ^C to the process.  The ascii code for '^C' is 3
             # (the character is known as ETX for 'End of Text', see
             # curses.ascii.ETX).
             child.sendline(chr(3))
             # Read and print any more output the program might produce on its
             # way out.
             try:
                 out_size = len(child.before)
                 child.expect_list(patterns, self.terminate_timeout)
                 print(child.before[out_size:], end='')
+                sys.stdout.flush()
             except KeyboardInterrupt:
                 # Impatient users tend to type it multiple times
                 pass
             finally:
                 # Ensure the subprocess really is terminated
                 child.terminate(force=True)
 
     def _make_cmd(self, cmd):
         return '%s -c "%s"' % (self.sh, cmd)
 
 
 # Make system() with a functional interface for outside use.  Note that we use
 # getoutput() from the _common utils, which is built on top of popen(). Using
 # pexpect to get subprocess output produces difficult to parse output, since
 # programs think they are talking to a tty and produce highly formatted output
 # (ls is a good example) that makes them hard.
 system = ProcessHandler().system