[pr6953-docs] update docstrings/whatsnew/shell.rst for env/set_env magic

docs/source/whatsnew/pr/env_magic.md

@@ -0,0 +1,1 b''
+* Enhanced support for `env` magic.  As before, `env` with no arguments displays all environment variables and values.  Additionally, `env` can be used to get or set individual environment variables.  To display an individual value, use the `env var` syntax.  To set a value, use `env var val` or `env var=val`.  Python value expansion using `$` works as usual.

IPython/core/magics/osm.py

@@ -1,785 +1,796 b''
 """Implementation of magic functions for interaction with the OS.
 
 Note: this module is named 'osm' instead of 'os' to avoid a collision with the
 builtin.
 """
 from __future__ import print_function
 #-----------------------------------------------------------------------------
 #  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 io
 import os
 import re
 import sys
 from pprint import pformat
 
 # Our own packages
 from IPython.core import magic_arguments
 from IPython.core import oinspect
 from IPython.core import page
 from IPython.core.alias import AliasError, Alias
 from IPython.core.error import UsageError
 from IPython.core.magic import  (
     Magics, compress_dhist, magics_class, line_magic, cell_magic, line_cell_magic
 )
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils.openpy import source_to_unicode
 from IPython.utils.path import unquote_filename
 from IPython.utils.process import abbrev_cwd
 from IPython.utils import py3compat
 from IPython.utils.py3compat import unicode_type
 from IPython.utils.terminal import set_term_title
 
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
 @magics_class
 class OSMagics(Magics):
     """Magics to interact with the underlying OS (shell-type functionality).
     """
 
     @skip_doctest
     @line_magic
     def alias(self, parameter_s=''):
         """Define an alias for a system command.
 
         '%alias alias_name cmd' defines 'alias_name' as an alias for 'cmd'
 
         Then, typing 'alias_name params' will execute the system command 'cmd
         params' (from your underlying operating system).
 
         Aliases have lower precedence than magic functions and Python normal
         variables, so if 'foo' is both a Python variable and an alias, the
         alias can not be executed until 'del foo' removes the Python variable.
 
         You can use the %l specifier in an alias definition to represent the
         whole line when the alias is called.  For example::
 
           In [2]: alias bracket echo "Input in brackets: <%l>"
           In [3]: bracket hello world
           Input in brackets: <hello world>
 
         You can also define aliases with parameters using %s specifiers (one
         per parameter)::
 
           In [1]: alias parts echo first %s second %s
           In [2]: %parts A B
           first A second B
           In [3]: %parts A
           Incorrect number of arguments: 2 expected.
           parts is an alias to: 'echo first %s second %s'
 
         Note that %l and %s are mutually exclusive.  You can only use one or
         the other in your aliases.
 
         Aliases expand Python variables just like system calls using ! or !!
         do: all expressions prefixed with '$' get expanded.  For details of
         the semantic rules, see PEP-215:
         http://www.python.org/peps/pep-0215.html.  This is the library used by
         IPython for variable expansion.  If you want to access a true shell
         variable, an extra $ is necessary to prevent its expansion by
         IPython::
 
           In [6]: alias show echo
           In [7]: PATH='A Python string'
           In [8]: show $PATH
           A Python string
           In [9]: show $$PATH
           /usr/local/lf9560/bin:/usr/local/intel/compiler70/ia32/bin:...
 
         You can use the alias facility to acess all of $PATH.  See the %rehash
         and %rehashx functions, which automatically create aliases for the
         contents of your $PATH.
 
         If called with no parameters, %alias prints the current alias table."""
 
         par = parameter_s.strip()
         if not par:
             aliases = sorted(self.shell.alias_manager.aliases)
             # stored = self.shell.db.get('stored_aliases', {} )
             # for k, v in stored:
             #     atab.append(k, v[0])
 
             print("Total number of aliases:", len(aliases))
             sys.stdout.flush()
             return aliases
 
         # Now try to define a new one
         try:
             alias,cmd = par.split(None, 1)
         except TypeError:
             print(oinspect.getdoc(self.alias))
             return
         
         try:
             self.shell.alias_manager.define_alias(alias, cmd)
         except AliasError as e:
             print(e)
     # end magic_alias
 
     @line_magic
     def unalias(self, parameter_s=''):
         """Remove an alias"""
 
         aname = parameter_s.strip()
         try:
             self.shell.alias_manager.undefine_alias(aname)
         except ValueError as e:
             print(e)
             return
         
         stored = self.shell.db.get('stored_aliases', {} )
         if aname in stored:
             print("Removing %stored alias",aname)
             del stored[aname]
             self.shell.db['stored_aliases'] = stored
 
     @line_magic
     def rehashx(self, parameter_s=''):
         """Update the alias table with all executable files in $PATH.
 
         This version explicitly checks that every entry in $PATH is a file
         with execute access (os.X_OK), so it is much slower than %rehash.
 
         Under Windows, it checks executability as a match against a
         '|'-separated string of extensions, stored in the IPython config
         variable win_exec_ext.  This defaults to 'exe|com|bat'.
 
         This function also resets the root module cache of module completer,
         used on slow filesystems.
         """
         from IPython.core.alias import InvalidAliasError
 
         # for the benefit of module completer in ipy_completers.py
         del self.shell.db['rootmodules_cache']
 
         path = [os.path.abspath(os.path.expanduser(p)) for p in
             os.environ.get('PATH','').split(os.pathsep)]
 
         syscmdlist = []
         # Now define isexec in a cross platform manner.
         if os.name == 'posix':
             isexec = lambda fname:os.path.isfile(fname) and \
                      os.access(fname,os.X_OK)
         else:
             try:
                 winext = os.environ['pathext'].replace(';','|').replace('.','')
             except KeyError:
                 winext = 'exe|com|bat|py'
             if 'py' not in winext:
                 winext += '|py'
             execre = re.compile(r'(.*)\.(%s)$' % winext,re.IGNORECASE)
             isexec = lambda fname:os.path.isfile(fname) and execre.match(fname)
         savedir = py3compat.getcwd()
 
         # Now walk the paths looking for executables to alias.
         try:
             # write the whole loop for posix/Windows so we don't have an if in
             # the innermost part
             if os.name == 'posix':
                 for pdir in path:
                     try:
                         os.chdir(pdir)
                         dirlist = os.listdir(pdir)
                     except OSError:
                         continue
                     for ff in dirlist:
                         if isexec(ff):
                             try:
                                 # Removes dots from the name since ipython
                                 # will assume names with dots to be python.
                                 if not self.shell.alias_manager.is_alias(ff):
                                     self.shell.alias_manager.define_alias(
                                         ff.replace('.',''), ff)
                             except InvalidAliasError:
                                 pass
                             else:
                                 syscmdlist.append(ff)
             else:
                 no_alias = Alias.blacklist
                 for pdir in path:
                     try:
                         os.chdir(pdir)
                         dirlist = os.listdir(pdir)
                     except OSError:
                         continue
                     for ff in dirlist:
                         base, ext = os.path.splitext(ff)
                         if isexec(ff) and base.lower() not in no_alias:
                             if ext.lower() == '.exe':
                                 ff = base
                                 try:
                                     # Removes dots from the name since ipython
                                     # will assume names with dots to be python.
                                     self.shell.alias_manager.define_alias(
                                         base.lower().replace('.',''), ff)
                                 except InvalidAliasError:
                                     pass
                                 syscmdlist.append(ff)
             self.shell.db['syscmdlist'] = syscmdlist
         finally:
             os.chdir(savedir)
 
     @skip_doctest
     @line_magic
     def pwd(self, parameter_s=''):
         """Return the current working directory path.
 
         Examples
         --------
         ::
 
           In [9]: pwd
           Out[9]: '/home/tsuser/sprint/ipython'
         """
         return py3compat.getcwd()
 
     @skip_doctest
     @line_magic
     def cd(self, parameter_s=''):
         """Change the current working directory.
 
         This command automatically maintains an internal list of directories
         you visit during your IPython session, in the variable _dh. The
         command %dhist shows this history nicely formatted. You can also
         do 'cd -<tab>' to see directory history conveniently.
 
         Usage:
 
           cd 'dir': changes to directory 'dir'.
 
           cd -: changes to the last visited directory.
 
           cd -<n>: changes to the n-th directory in the directory history.
 
           cd --foo: change to directory that matches 'foo' in history
 
           cd -b <bookmark_name>: jump to a bookmark set by %bookmark
              (note: cd <bookmark_name> is enough if there is no
               directory <bookmark_name>, but a bookmark with the name exists.)
               'cd -b <tab>' allows you to tab-complete bookmark names.
 
         Options:
 
         -q: quiet.  Do not print the working directory after the cd command is
         executed.  By default IPython's cd command does print this directory,
         since the default prompts do not display path information.
 
         Note that !cd doesn't work for this purpose because the shell where
         !command runs is immediately discarded after executing 'command'.
 
         Examples
         --------
         ::
 
           In [10]: cd parent/child
           /home/tsuser/parent/child
         """
 
         oldcwd = py3compat.getcwd()
         numcd = re.match(r'(-)(\d+)$',parameter_s)
         # jump in directory history by number
         if numcd:
             nn = int(numcd.group(2))
             try:
                 ps = self.shell.user_ns['_dh'][nn]
             except IndexError:
                 print('The requested directory does not exist in history.')
                 return
             else:
                 opts = {}
         elif parameter_s.startswith('--'):
             ps = None
             fallback = None
             pat = parameter_s[2:]
             dh = self.shell.user_ns['_dh']
             # first search only by basename (last component)
             for ent in reversed(dh):
                 if pat in os.path.basename(ent) and os.path.isdir(ent):
                     ps = ent
                     break
 
                 if fallback is None and pat in ent and os.path.isdir(ent):
                     fallback = ent
 
             # if we have no last part match, pick the first full path match
             if ps is None:
                 ps = fallback
 
             if ps is None:
                 print("No matching entry in directory history")
                 return
             else:
                 opts = {}
 
 
         else:
             #turn all non-space-escaping backslashes to slashes,
             # for c:\windows\directory\names\
             parameter_s = re.sub(r'\\(?! )','/', parameter_s)
             opts,ps = self.parse_options(parameter_s,'qb',mode='string')
         # jump to previous
         if ps == '-':
             try:
                 ps = self.shell.user_ns['_dh'][-2]
             except IndexError:
                 raise UsageError('%cd -: No previous directory to change to.')
         # jump to bookmark if needed
         else:
             if not os.path.isdir(ps) or 'b' in opts:
                 bkms = self.shell.db.get('bookmarks', {})
 
                 if ps in bkms:
                     target = bkms[ps]
                     print('(bookmark:%s) -> %s' % (ps, target))
                     ps = target
                 else:
                     if 'b' in opts:
                         raise UsageError("Bookmark '%s' not found.  "
                               "Use '%%bookmark -l' to see your bookmarks." % ps)
 
         # strip extra quotes on Windows, because os.chdir doesn't like them
         ps = unquote_filename(ps)
         # at this point ps should point to the target dir
         if ps:
             try:
                 os.chdir(os.path.expanduser(ps))
                 if hasattr(self.shell, 'term_title') and self.shell.term_title:
                     set_term_title('IPython: ' + abbrev_cwd())
             except OSError:
                 print(sys.exc_info()[1])
             else:
                 cwd = py3compat.getcwd()
                 dhist = self.shell.user_ns['_dh']
                 if oldcwd != cwd:
                     dhist.append(cwd)
                     self.shell.db['dhist'] = compress_dhist(dhist)[-100:]
 
         else:
             os.chdir(self.shell.home_dir)
             if hasattr(self.shell, 'term_title') and self.shell.term_title:
                 set_term_title('IPython: ' + '~')
             cwd = py3compat.getcwd()
             dhist = self.shell.user_ns['_dh']
 
             if oldcwd != cwd:
                 dhist.append(cwd)
                 self.shell.db['dhist'] = compress_dhist(dhist)[-100:]
         if not 'q' in opts and self.shell.user_ns['_dh']:
             print(self.shell.user_ns['_dh'][-1])
 
     @line_magic
     def env(self, parameter_s=''):
-        """List environment variables."""
+        """Get, set, or list environment variables.
+
+        Usage:\\
+
+          %env: lists all environment variables/values
+          %env var: get value for var
+          %env var val: set value for var
+          %env var=val: set value for var
+          %env var=$val: set value for var, using python expansion if possible
+        """
         if parameter_s.strip():
             split = '=' if '=' in parameter_s else ' '
             bits = parameter_s.split(split)
             if len(bits) == 1:
                 key = parameter_s.strip()
                 if key in os.environ:
                     return os.environ[key]
                 else:
                     err = "Environment does not have key: {0}".format(key)
                     raise UsageError(err)
             if len(bits) > 1:
                 return self.set_env(parameter_s)
         return dict(os.environ)
 
     @line_magic
     def set_env(self, parameter_s):
         """Set environment variables.  Assumptions are that either "val" is a
         name in the user namespace, or val is something that evaluates to a
         string.
 
         Usage:\\
-        %set_env var val
+          %set_env var val: set value for var
+          %set_env var=val: set value for var
+          %set_env var=$val: set value for var, using python expansion if possible
         """
         split = '=' if '=' in parameter_s else ' '
         bits = parameter_s.split(split, 1)
         if not parameter_s.strip() or len(bits)<2:
             raise UsageError("usage is 'set_env var=val'")
         var = bits[0].strip()
         val = bits[1].strip()
         if re.match(r'.*\s.*', var):
             # an environment variable with whitespace is almost certainly
             # not what the user intended.  what's more likely is the wrong
             # split was chosen, ie for "set_env cmd_args A=B", we chose
             # '=' for the split and should have chosen ' '.  to get around
             # this, users should just assign directly to os.environ or use
             # standard magic {var} expansion.
             err = "refusing to set env var with whitespace: '{0}'"
             err = err.format(val)
             raise UsageError(err)
         os.environ[py3compat.cast_bytes_py2(var)] = py3compat.cast_bytes_py2(val)
         print('env: {0}={1}'.format(var,val))
 
     @line_magic
     def pushd(self, parameter_s=''):
         """Place the current dir on stack and change directory.
 
         Usage:\\
           %pushd ['dirname']
         """
 
         dir_s = self.shell.dir_stack
         tgt = os.path.expanduser(unquote_filename(parameter_s))
         cwd = py3compat.getcwd().replace(self.shell.home_dir,'~')
         if tgt:
             self.cd(parameter_s)
         dir_s.insert(0,cwd)
         return self.shell.magic('dirs')
 
     @line_magic
     def popd(self, parameter_s=''):
         """Change to directory popped off the top of the stack.
         """
         if not self.shell.dir_stack:
             raise UsageError("%popd on empty stack")
         top = self.shell.dir_stack.pop(0)
         self.cd(top)
         print("popd ->",top)
 
     @line_magic
     def dirs(self, parameter_s=''):
         """Return the current directory stack."""
 
         return self.shell.dir_stack
 
     @line_magic
     def dhist(self, parameter_s=''):
         """Print your history of visited directories.
 
         %dhist       -> print full history\\
         %dhist n     -> print last n entries only\\
         %dhist n1 n2 -> print entries between n1 and n2 (n2 not included)\\
 
         This history is automatically maintained by the %cd command, and
         always available as the global list variable _dh. You can use %cd -<n>
         to go to directory number <n>.
 
         Note that most of time, you should view directory history by entering
         cd -<TAB>.
 
         """
 
         dh = self.shell.user_ns['_dh']
         if parameter_s:
             try:
                 args = map(int,parameter_s.split())
             except:
                 self.arg_err(self.dhist)
                 return
             if len(args) == 1:
                 ini,fin = max(len(dh)-(args[0]),0),len(dh)
             elif len(args) == 2:
                 ini,fin = args
                 fin = min(fin, len(dh))
             else:
                 self.arg_err(self.dhist)
                 return
         else:
             ini,fin = 0,len(dh)
         print('Directory history (kept in _dh)')
         for i in range(ini, fin):
             print("%d: %s" % (i, dh[i]))
 
     @skip_doctest
     @line_magic
     def sc(self, parameter_s=''):
         """Shell capture - run shell command and capture output (DEPRECATED use !).
 
         DEPRECATED. Suboptimal, retained for backwards compatibility.
 
         You should use the form 'var = !command' instead. Example:
 
          "%sc -l myfiles = ls ~" should now be written as
 
          "myfiles = !ls ~"
 
         myfiles.s, myfiles.l and myfiles.n still apply as documented
         below.
 
         --
         %sc [options] varname=command
 
         IPython will run the given command using commands.getoutput(), and
         will then update the user's interactive namespace with a variable
         called varname, containing the value of the call.  Your command can
         contain shell wildcards, pipes, etc.
 
         The '=' sign in the syntax is mandatory, and the variable name you
         supply must follow Python's standard conventions for valid names.
 
         (A special format without variable name exists for internal use)
 
         Options:
 
           -l: list output.  Split the output on newlines into a list before
           assigning it to the given variable.  By default the output is stored
           as a single string.
 
           -v: verbose.  Print the contents of the variable.
 
         In most cases you should not need to split as a list, because the
         returned value is a special type of string which can automatically
         provide its contents either as a list (split on newlines) or as a
         space-separated string.  These are convenient, respectively, either
         for sequential processing or to be passed to a shell command.
 
         For example::
 
             # Capture into variable a
             In [1]: sc a=ls *py
 
             # a is a string with embedded newlines
             In [2]: a
             Out[2]: 'setup.py\\nwin32_manual_post_install.py'
 
             # which can be seen as a list:
             In [3]: a.l
             Out[3]: ['setup.py', 'win32_manual_post_install.py']
 
             # or as a whitespace-separated string:
             In [4]: a.s
             Out[4]: 'setup.py win32_manual_post_install.py'
 
             # a.s is useful to pass as a single command line:
             In [5]: !wc -l $a.s
               146 setup.py
               130 win32_manual_post_install.py
               276 total
 
             # while the list form is useful to loop over:
             In [6]: for f in a.l:
               ...:      !wc -l $f
               ...:
             146 setup.py
             130 win32_manual_post_install.py
 
         Similarly, the lists returned by the -l option are also special, in
         the sense that you can equally invoke the .s attribute on them to
         automatically get a whitespace-separated string from their contents::
 
             In [7]: sc -l b=ls *py
 
             In [8]: b
             Out[8]: ['setup.py', 'win32_manual_post_install.py']
 
             In [9]: b.s
             Out[9]: 'setup.py win32_manual_post_install.py'
 
         In summary, both the lists and strings used for output capture have
         the following special attributes::
 
             .l (or .list) : value as list.
             .n (or .nlstr): value as newline-separated string.
             .s (or .spstr): value as space-separated string.
         """
 
         opts,args = self.parse_options(parameter_s, 'lv')
         # Try to get a variable name and command to run
         try:
             # the variable name must be obtained from the parse_options
             # output, which uses shlex.split to strip options out.
             var,_ = args.split('=', 1)
             var = var.strip()
             # But the command has to be extracted from the original input
             # parameter_s, not on what parse_options returns, to avoid the
             # quote stripping which shlex.split performs on it.
             _,cmd = parameter_s.split('=', 1)
         except ValueError:
             var,cmd = '',''
         # If all looks ok, proceed
         split = 'l' in opts
         out = self.shell.getoutput(cmd, split=split)
         if 'v' in opts:
             print('%s ==\n%s' % (var, pformat(out)))
         if var:
             self.shell.user_ns.update({var:out})
         else:
             return out
 
     @line_cell_magic
     def sx(self, line='', cell=None):
         """Shell execute - run shell command and capture output (!! is short-hand).
 
         %sx command
 
         IPython will run the given command using commands.getoutput(), and
         return the result formatted as a list (split on '\\n').  Since the
         output is _returned_, it will be stored in ipython's regular output
         cache Out[N] and in the '_N' automatic variables.
 
         Notes:
 
         1) If an input line begins with '!!', then %sx is automatically
         invoked.  That is, while::
 
           !ls
 
         causes ipython to simply issue system('ls'), typing::
 
           !!ls
 
         is a shorthand equivalent to::
 
           %sx ls
 
         2) %sx differs from %sc in that %sx automatically splits into a list,
         like '%sc -l'.  The reason for this is to make it as easy as possible
         to process line-oriented shell output via further python commands.
         %sc is meant to provide much finer control, but requires more
         typing.
 
         3) Just like %sc -l, this is a list with special attributes:
         ::
 
           .l (or .list) : value as list.
           .n (or .nlstr): value as newline-separated string.
           .s (or .spstr): value as whitespace-separated string.
 
         This is very useful when trying to use such lists as arguments to
         system commands."""
         
         if cell is None:
             # line magic
             return self.shell.getoutput(line)
         else:
             opts,args = self.parse_options(line, '', 'out=')
             output = self.shell.getoutput(cell)
             out_name = opts.get('out', opts.get('o'))
             if out_name:
                 self.shell.user_ns[out_name] = output
             else:
                 return output
 
     system = line_cell_magic('system')(sx)
     bang = cell_magic('!')(sx)
 
     @line_magic
     def bookmark(self, parameter_s=''):
         """Manage IPython's bookmark system.
 
         %bookmark <name>       - set bookmark to current dir
         %bookmark <name> <dir> - set bookmark to <dir>
         %bookmark -l           - list all bookmarks
         %bookmark -d <name>    - remove bookmark
         %bookmark -r           - remove all bookmarks
 
         You can later on access a bookmarked folder with::
 
           %cd -b <name>
 
         or simply '%cd <name>' if there is no directory called <name> AND
         there is such a bookmark defined.
 
         Your bookmarks persist through IPython sessions, but they are
         associated with each profile."""
 
         opts,args = self.parse_options(parameter_s,'drl',mode='list')
         if len(args) > 2:
             raise UsageError("%bookmark: too many arguments")
 
         bkms = self.shell.db.get('bookmarks',{})
 
         if 'd' in opts:
             try:
                 todel = args[0]
             except IndexError:
                 raise UsageError(
                     "%bookmark -d: must provide a bookmark to delete")
             else:
                 try:
                     del bkms[todel]
                 except KeyError:
                     raise UsageError(
                         "%%bookmark -d: Can't delete bookmark '%s'" % todel)
 
         elif 'r' in opts:
             bkms = {}
         elif 'l' in opts:
             bks = sorted(bkms)
             if bks:
                 size = max(map(len, bks))
             else:
                 size = 0
             fmt = '%-'+str(size)+'s -> %s'
             print('Current bookmarks:')
             for bk in bks:
                 print(fmt % (bk, bkms[bk]))
         else:
             if not args:
                 raise UsageError("%bookmark: You must specify the bookmark name")
             elif len(args)==1:
                 bkms[args[0]] = py3compat.getcwd()
             elif len(args)==2:
                 bkms[args[0]] = args[1]
         self.shell.db['bookmarks'] = bkms
 
     @line_magic
     def pycat(self, parameter_s=''):
         """Show a syntax-highlighted file through a pager.
 
         This magic is similar to the cat utility, but it will assume the file
         to be Python source and will show it with syntax highlighting.
 
         This magic command can either take a local filename, an url,
         an history range (see %history) or a macro as argument ::
 
         %pycat myscript.py
         %pycat 7-27
         %pycat myMacro
         %pycat http://www.example.com/myscript.py
         """
         if not parameter_s:
             raise UsageError('Missing filename, URL, input history range, '
                              'or macro.')
 
         try :
             cont = self.shell.find_user_code(parameter_s, skip_encoding_cookie=False)
         except (ValueError, IOError):
             print("Error: no such file, variable, URL, history range or macro")
             return
 
         page.page(self.shell.pycolorize(source_to_unicode(cont)))
 
     @magic_arguments.magic_arguments()
     @magic_arguments.argument(
         '-a', '--append', action='store_true', default=False,
         help='Append contents of the cell to an existing file. '
              'The file will be created if it does not exist.'
     )
     @magic_arguments.argument(
         'filename', type=unicode_type,
         help='file to write'
     )
     @cell_magic
     def writefile(self, line, cell):
         """Write the contents of the cell to a file.
         
         The file will be overwritten unless the -a (--append) flag is specified.
         """
         args = magic_arguments.parse_argstring(self.writefile, line)
         filename = os.path.expanduser(unquote_filename(args.filename))
         
         if os.path.exists(filename):
             if args.append:
                 print("Appending to %s" % filename)
             else:
                 print("Overwriting %s" % filename)
         else:
             print("Writing %s" % filename)
         
         mode = 'a' if args.append else 'w'
         with io.open(filename, mode, encoding='utf-8') as f:
             f.write(cell)

docs/source/interactive/shell.rst

@@ -1,201 +1,213 b''
 .. _ipython_as_shell:
 
 =========================
 IPython as a system shell
 =========================
 
 
 
 Overview
 ========
 
 It is possible to adapt IPython for system shell usage. In the past, IPython
 shipped a special 'sh' profile for this purpose, but it had been quarantined
 since 0.11 release, and in 1.0 it was removed altogether. Nevertheless, much
 of this section relies on machinery which does not require a custom profile.
 
 You can set up your own 'sh' :ref:`profile <Profiles>` to be different from
 the default profile such that:
 
  * Prompt shows the current directory (see `Prompt customization`_)
  * Make system commands directly available (in alias table) by running the
    ``%rehashx`` magic. If you install new programs along your PATH, you might
    want to run ``%rehashx`` to update the alias table
  * turn ``%autocall`` to full mode
 
 
+Environment variables
+=====================
+
+Rather than manipulating os.environ directly, you may like to use the magic
+`%env` command.  With no arguments, this displays all environment variables
+and values.  To get the value of a specific variable, use `%env var`.  To set
+the value of a specific variable, use `%env foo bar`, `%env foo=bar`.  By
+default values are considered to be strings so quoting them is unnecessary.
+However, python variables are expanded as usual in the magic command, so
+`%env foo=$bar` means "set the environment variable foo to the value of the
+python variable `bar`".
+
 Aliases
 =======
 
 Once you run ``%rehashx``, all of your $PATH has been loaded as IPython aliases,
 so you should be able to type any normal system command and have it executed.
 See ``%alias?``  and ``%unalias?`` for details on the alias facilities. See also
 ``%rehashx?`` for details on the mechanism used to load $PATH.
 
 
 Directory management
 ====================
 
 Since each command passed by ipython to the underlying system is executed
 in a subshell which exits immediately, you can NOT use !cd to navigate
 the filesystem.
 
 IPython provides its own builtin ``%cd`` magic command to move in the
 filesystem (the % is not required with automagic on). It also maintains
 a list of visited directories (use ``%dhist`` to see it) and allows direct
 switching to any of them. Type ``cd?`` for more details.
 
 ``%pushd``, ``%popd`` and ``%dirs`` are provided for directory stack handling.
 
 
 Prompt customization
 ====================
 
 Here are some prompt configurations you can try out interactively by using the
 ``%config`` magic::
     
     %config PromptManager.in_template = r'{color.LightGreen}\u@\h{color.LightBlue}[{color.LightCyan}\Y1{color.LightBlue}]{color.Green}|\#> '
     %config PromptManager.in2_template = r'{color.Green}|{color.LightGreen}\D{color.Green}> '
     %config PromptManager.out_template = r'<\#> '
 
 
 You can change the prompt configuration to your liking permanently by editing
 ``ipython_config.py``::
     
     c.PromptManager.in_template = r'{color.LightGreen}\u@\h{color.LightBlue}[{color.LightCyan}\Y1{color.LightBlue}]{color.Green}|\#> '
     c.PromptManager.in2_template = r'{color.Green}|{color.LightGreen}\D{color.Green}> '
     c.PromptManager.out_template = r'<\#> '
 
 Read more about the :ref:`configuration system <config_overview>` for details
 on how to find ``ipython_config.py``.
 
 .. _string_lists:
 
 String lists
 ============
 
 String lists (IPython.utils.text.SList) are handy way to process output
 from system commands. They are produced by ``var = !cmd`` syntax.
 
 First, we acquire the output of 'ls -l'::
 
     [Q:doc/examples]|2> lines = !ls -l
      ==
     ['total 23',
      '-rw-rw-rw- 1 ville None 1163 Sep 30  2006 example-demo.py',
      '-rw-rw-rw- 1 ville None 1927 Sep 30  2006 example-embed-short.py',
      '-rwxrwxrwx 1 ville None 4606 Sep  1 17:15 example-embed.py',
      '-rwxrwxrwx 1 ville None 1017 Sep 30  2006 example-gnuplot.py',
      '-rwxrwxrwx 1 ville None  339 Jun 11 18:01 extension.py',
      '-rwxrwxrwx 1 ville None  113 Dec 20  2006 seteditor.py',
      '-rwxrwxrwx 1 ville None  245 Dec 12  2006 seteditor.pyc']
 
 Now, let's take a look at the contents of 'lines' (the first number is
 the list element number)::
 
     [Q:doc/examples]|3> lines
                     <3> SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
 
     0: total 23
     1: -rw-rw-rw- 1 ville None 1163 Sep 30  2006 example-demo.py
     2: -rw-rw-rw- 1 ville None 1927 Sep 30  2006 example-embed-short.py
     3: -rwxrwxrwx 1 ville None 4606 Sep  1 17:15 example-embed.py
     4: -rwxrwxrwx 1 ville None 1017 Sep 30  2006 example-gnuplot.py
     5: -rwxrwxrwx 1 ville None  339 Jun 11 18:01 extension.py
     6: -rwxrwxrwx 1 ville None  113 Dec 20  2006 seteditor.py
     7: -rwxrwxrwx 1 ville None  245 Dec 12  2006 seteditor.pyc
 
 Now, let's filter out the 'embed' lines::
 
     [Q:doc/examples]|4> l2 = lines.grep('embed',prune=1)
     [Q:doc/examples]|5> l2
                     <5> SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
 
     0: total 23
     1: -rw-rw-rw- 1 ville None 1163 Sep 30  2006 example-demo.py
     2: -rwxrwxrwx 1 ville None 1017 Sep 30  2006 example-gnuplot.py
     3: -rwxrwxrwx 1 ville None  339 Jun 11 18:01 extension.py
     4: -rwxrwxrwx 1 ville None  113 Dec 20  2006 seteditor.py
     5: -rwxrwxrwx 1 ville None  245 Dec 12  2006 seteditor.pyc
 
 Now, we want strings having just file names and permissions::
 
     [Q:doc/examples]|6> l2.fields(8,0)
                     <6> SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
 
     0: total
     1: example-demo.py -rw-rw-rw-
     2: example-gnuplot.py -rwxrwxrwx
     3: extension.py -rwxrwxrwx
     4: seteditor.py -rwxrwxrwx
     5: seteditor.pyc -rwxrwxrwx
 
 Note how the line with 'total' does not raise IndexError.
 
 If you want to split these (yielding lists), call fields() without
 arguments::
 
     [Q:doc/examples]|7> _.fields()
                     <7>
     [['total'],
      ['example-demo.py', '-rw-rw-rw-'],
      ['example-gnuplot.py', '-rwxrwxrwx'],
      ['extension.py', '-rwxrwxrwx'],
      ['seteditor.py', '-rwxrwxrwx'],
      ['seteditor.pyc', '-rwxrwxrwx']]
 
 If you want to pass these separated with spaces to a command (typical
 for lists if files), use the .s property::
 
 
     [Q:doc/examples]|13> files = l2.fields(8).s
     [Q:doc/examples]|14> files
                     <14> 'example-demo.py example-gnuplot.py extension.py seteditor.py seteditor.pyc'
     [Q:doc/examples]|15> ls $files
     example-demo.py  example-gnuplot.py  extension.py  seteditor.py  seteditor.pyc
 
 SLists are inherited from normal python lists, so every list method is
 available::
 
     [Q:doc/examples]|21> lines.append('hey')
 
 
 Real world example: remove all files outside version control
 ------------------------------------------------------------
 
 First, capture output of "hg status"::
 
     [Q:/ipython]|28> out = !hg status
      ==
     ['M IPython\\extensions\\ipy_kitcfg.py',
      'M IPython\\extensions\\ipy_rehashdir.py',
     ...
      '? build\\lib\\IPython\\Debugger.py',
      '? build\\lib\\IPython\\extensions\\InterpreterExec.py',
      '? build\\lib\\IPython\\extensions\\InterpreterPasteInput.py',
     ...
 
 (lines starting with ? are not under version control).
 
 ::
 
     [Q:/ipython]|35> junk = out.grep(r'^\?').fields(1)
     [Q:/ipython]|36> junk
                 <36> SList (.p, .n, .l, .s, .grep(), .fields() availab
     ...
     10: build\bdist.win32\winexe\temp\_ctypes.py
     11: build\bdist.win32\winexe\temp\_hashlib.py
     12: build\bdist.win32\winexe\temp\_socket.py
 
 Now we can just remove these files by doing 'rm $junk.s'. 
 
 The .s, .n, .p properties
 -------------------------
 
 The ``.s`` property returns one string where lines are separated by
 single space (for convenient passing to system commands). The ``.n``
 property return one string where the lines are separated by a newline
 (i.e. the original output of the function). If the items in string
 list are file names, ``.p`` can be used to get a list of "path" objects
 for convenient file manipulation.