Add --proc option to %%script

This change allows, for example, user to terminate the process started
by %%script cell magic.

IPython/core/magics/script.py

@@ -1,216 +1,224 b''
 """Magic functions for running cells in various scripts."""
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012 The IPython Development Team.
 #
 #  Distributed under the terms of the Modified BSD License.
 #
 #  The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Stdlib
 import os
 import re
 import sys
 from subprocess import Popen, PIPE
 
 # Our own packages
 from IPython.config.configurable import Configurable
 from IPython.core import magic_arguments
 from IPython.core.error import UsageError
 from IPython.core.magic import  (
     Magics, magics_class, line_magic, cell_magic
 )
 from IPython.lib.backgroundjobs import BackgroundJobManager
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import py3compat
 from IPython.utils.process import find_cmd, FindCmdError, arg_split
 from IPython.utils.traitlets import List, Dict
 
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
 
 def script_args(f):
     """single decorator for adding script args"""
     args = [
         magic_arguments.argument(
             '--out', type=str,
             help="""The variable in which to store stdout from the script.
             If the script is backgrounded, this will be the stdout *pipe*,
             instead of the stderr text itself.
             """
         ),
         magic_arguments.argument(
             '--err', type=str,
             help="""The variable in which to store stderr from the script.
             If the script is backgrounded, this will be the stderr *pipe*,
             instead of the stderr text itself.
             """
         ),
         magic_arguments.argument(
             '--bg', action="store_true",
             help="""Whether to run the script in the background.
             If given, the only way to see the output of the command is
             with --out/err.
             """
         ),
+        magic_arguments.argument(
+            '--proc', type=str,
+            help="""The variable in which to store Popen instance.
+            This is used only when --bg option is given.
+            """
+        ),
     ]
     for arg in args:
         f = arg(f)
     return f
 
 @magics_class
 class ScriptMagics(Magics, Configurable):
     """Magics for talking to scripts
     
     This defines a base `%%script` cell magic for running a cell
     with a program in a subprocess, and registers a few top-level
     magics that call %%script with common interpreters.
     """
     script_magics = List(config=True,
         help="""Extra script cell magics to define
         
         This generates simple wrappers of `%%script foo` as `%%foo`.
         
         If you want to add script magics that aren't on your path,
         specify them in script_paths
         """,
     )
     def _script_magics_default(self):
         """default to a common list of programs if we find them"""
         
         defaults = []
         to_try = []
         if os.name == 'nt':
             defaults.append('cmd')
             to_try.append('powershell')
         to_try.extend([
             'sh',
             'bash',
             'perl',
             'ruby',
             'python3',
             'pypy',
         ])
         
         for cmd in to_try:
             if cmd in self.script_paths:
                 defaults.append(cmd)
             else:
                 try:
                     find_cmd(cmd)
                 except FindCmdError:
                     # command not found, ignore it
                     pass
                 except ImportError:
                     # Windows without pywin32, find_cmd doesn't work
                     pass
                 else:
                     defaults.append(cmd)
         return defaults
     
     script_paths = Dict(config=True,
         help="""Dict mapping short 'ruby' names to full paths, such as '/opt/secret/bin/ruby'
         
         Only necessary for items in script_magics where the default path will not
         find the right interpreter.
         """
     )
     
     def __init__(self, shell=None):
         Configurable.__init__(self, config=shell.config)
         self._generate_script_magics()
         Magics.__init__(self, shell=shell)
         self.job_manager = BackgroundJobManager()
     
     def _generate_script_magics(self):
         cell_magics = self.magics['cell']
         for name in self.script_magics:
             cell_magics[name] = self._make_script_magic(name)
     
     def _make_script_magic(self, name):
         """make a named magic, that calls %%script with a particular program"""
         # expand to explicit path if necessary:
         script = self.script_paths.get(name, name)
         
         @magic_arguments.magic_arguments()
         @script_args
         def named_script_magic(line, cell):
             # if line, add it as cl-flags
             if line:
                  line = "%s %s" % (script, line)
             else:
                 line = script
             return self.shebang(line, cell)
         
         # write a basic docstring:
         named_script_magic.__doc__ = \
         """%%{name} script magic
         
         Run cells with {script} in a subprocess.
         
         This is a shortcut for `%%script {script}`
         """.format(**locals())
         
         return named_script_magic
     
     @magic_arguments.magic_arguments()
     @script_args
     @cell_magic("script")
     def shebang(self, line, cell):
         """Run a cell via a shell command
         
         The `%%script` line is like the #! line of script,
         specifying a program (bash, perl, ruby, etc.) with which to run.
         
         The rest of the cell is run by that program.
         
         Examples
         --------
         ::
         
             In [1]: %%script bash
                ...: for i in 1 2 3; do
                ...:   echo $i
                ...: done
             1
             2
             3
         """
         argv = arg_split(line, posix = not sys.platform.startswith('win'))
         args, cmd = self.shebang.parser.parse_known_args(argv)
 
         p = Popen(cmd, stdout=PIPE, stderr=PIPE, stdin=PIPE)
         
         cell = cell.encode('utf8', 'replace')
         if args.bg:
             if args.out:
                 self.shell.user_ns[args.out] = p.stdout
             if args.err:
                 self.shell.user_ns[args.err] = p.stderr
             self.job_manager.new(self._run_script, p, cell)
+            if args.proc:
+                self.shell.user_ns[args.proc] = p
             return
         
         out, err = p.communicate(cell)
         out = py3compat.bytes_to_str(out)
         err = py3compat.bytes_to_str(err)
         if args.out:
             self.shell.user_ns[args.out] = out
         else:
             sys.stdout.write(out)
             sys.stdout.flush()
         if args.err:
             self.shell.user_ns[args.err] = err
         else:
             sys.stderr.write(err)
             sys.stderr.flush()
     
     def _run_script(self, p, cell):
         """callback for running the script in the background"""
         p.stdin.write(cell)
         p.stdin.close()
         p.wait()