Index: Doc/library/subprocess.rst
===================================================================
--- Doc/library/subprocess.rst	(revision 77827)
+++ Doc/library/subprocess.rst	(working copy)
@@ -48,14 +48,37 @@
 
    On Unix, with *shell=False* (default): In this case, the Popen class uses
    :meth:`os.execvp` to execute the child program. *args* should normally be a
-   sequence.  A string will be treated as a sequence with the string as the only
-   item (the program to execute).
-
-   On Unix, with *shell=True*: If args is a string, it specifies the command string
-   to execute through the shell.  If *args* is a sequence, the first item specifies
-   the command string, and any additional items will be treated as additional shell
+   sequence.  If a string is specified for *args*, it will be used as the name
+   of the program to execute; this will only work if the program takes no
    arguments.
 
+   .. note::
+
+      :meth:`shlex.split` can be useful when determining the correct
+      tokenization for *args*, especially in complex cases::
+
+         >>> import shlex
+         >>> command_line = raw_input()
+         /bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "python -c 'print __name__'"
+         >>> shlex.split(command_line)
+         ['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "python -c 'print __name__'"]
+
+      Note in particular that options and arguments that are separated
+      by whitespace in the shell go in separate list elements, while
+      arguments that need quoting when used in the shell (such as
+      filenames containing spaces or the python command shown above)
+      are single list elements.
+
+   On Unix, with *shell=True*:  If args is a string, it specifies the command
+   string to execute through the shell.  This means that the string must be
+   formatted exactly as it would be when typed at the shell prompt.  This
+   includes, for example, quoting filenames with spaces in them.  Additional
+   quoting may be required because the entire string is a Python string.  It
+   may be useful to use a Python raw string in complex cases.  If *args* is a
+   sequence, the first item specifies the command string, and any additional
+   items will be treated as additional arguments to the shell itself, following
+   the "-c" and the specified command string in the call to the shell.
+
    On Windows: the :class:`Popen` class uses CreateProcess() to execute the child
    program, which operates on strings.  If *args* is a sequence, it will be
    converted to a string using the :meth:`list2cmdline` method.  Please note that