On 03/06/2017 03:18 AM, Markus Armbruster wrote:
> Nir Soffer <nir...@gmail.com> writes:
>
>> On Fri, Mar 3, 2017 at 9:29 PM, John Snow <js...@redhat.com> wrote:
>>>
>>>
>>> On 03/03/2017 02:26 PM, Nir Soffer wrote:
>>>> On Fri, Mar 3, 2017 at 8:54 PM, John Snow <js...@redhat.com> wrote:
>>>>> Use the existing readline history function we are utilizing
>>>>> to provide persistent command history across instances of qmp-shell.
>>>>>
>>>>> This assists entering debug commands across sessions that may be
>>>>> interrupted by QEMU sessions terminating, where the qmp-shell has
>>>>> to be relaunched.
>>>>>
>>>>> Signed-off-by: John Snow <js...@redhat.com>
>>>>> ---
>>>>>
>>>>> v2: Adjusted the errors to whine about non-ENOENT errors, but still
>>>>> intercept all errors as non-fatal.
>>>>> Save history atexit() to match bash standard behavior
>>>>>
>>>>> scripts/qmp/qmp-shell | 19 +++++++++++++++++++
>>>>> 1 file changed, 19 insertions(+)
>>>>>
>>>>> diff --git a/scripts/qmp/qmp-shell b/scripts/qmp/qmp-shell
>>>>> index 0373b24..55a8285 100755
>>>>> --- a/scripts/qmp/qmp-shell
>>>>> +++ b/scripts/qmp/qmp-shell
>>>>> @@ -70,6 +70,9 @@ import json
>>>>> import ast
>>>>> import readline
>>>>> import sys
>>>>> +import os
>>>>> +import errno
>>>>> +import atexit
>>>>>
>>>>> class QMPCompleter(list):
>>>>> def complete(self, text, state):
>>>>> @@ -109,6 +112,7 @@ class QMPShell(qmp.QEMUMonitorProtocol):
>>>>> self._pretty = pretty
>>>>> self._transmode = False
>>>>> self._actions = list()
>>>>> + self._histfile = os.path.join(os.path.expanduser('~'),
>>>>> '.qmp_history')
>
> I selfishly object to this filename, because I'm using it with
>
> $ socat UNIX:/work/armbru/images/test-qmp
> READLINE,history=$HOME/.qmp_history,prompt='QMP> '
>
> Just kidding. But seriously, shouldn't this be named after the
> *application* (qmp-shell) rather than the protocol (qmp)?
>
Seeing as the history itself is the qmp-shell syntax, you are correct.
(Hey, it would be interesting to store the generated QMP into the
qmp_history, though...!)
>>>>>
>>>>> def __get_address(self, arg):
>>>>> """
>>>>> @@ -137,6 +141,21 @@ class QMPShell(qmp.QEMUMonitorProtocol):
>>>>> # XXX: default delimiters conflict with some command names (eg.
>>>>> query-),
>>>>> # clearing everything as it doesn't seem to matter
>>>>> readline.set_completer_delims('')
>>>>> + try:
>>>>> + readline.read_history_file(self._histfile)
>>>>> + except Exception as e:
>>>>> + if isinstance(e, IOError) and e.errno == errno.ENOENT:
>>>>> + # File not found. No problem.
>>>>> + pass
>>>>> + else:
>>>>> + print "Failed to read history '%s'; %s" %
>>>>> (self._histfile, e)
>>>>
>>>> I would handle only IOError, since any other error means a bug in this code
>>>> or in the underlying readline library, and the best way to handle this is
>>>> to
>>>> let it fail loudly.
>>>>
>>>
>>> Disagree. No reason to stop the shell from working because a QOL feature
>>> didn't initialize correctly.
>>>
>>> The warning will be enough to solicit reports and fixes if necessary.
>>
>> I agree, the current solution is good tradeoff.
>
> For what it's worth, bash seems to silently ignore a history file it
> can't read. Tested by running "HISTFILE=xxx bash", then chmod 0 xxx, da
> capo.
>
Right, done by example.
>> One thing missing, is a call to readline.set_history_length, without
>> it the history
>> will grow without limit, see:
>> https://docs.python.org/2/library/readline.html#readline.set_history_length
>
> Should this be addressed for 2.9?
>
You can add a limit if you want to; I don't have suggestions for which
completely arbitrary limit makes sense, so I left it blank intentionally.
>>>>> + atexit.register(self.__save_history)
>>>>> +
>>>>> + def __save_history(self):
>>>>> + try:
>>>>> + readline.write_history_file(self._histfile)
>>>>> + except Exception as e:
>>>>> + print "Failed to save history file '%s'; %s" %
>>>>> (self._histfile, e)
>>>>>
>>>>> def __parse_value(self, val):
>>>>> try:
>>>>
>>>> But I think this is good enough and useful as is.
>>>>
>>>> Reviewed-by: Nir Soffer <nir...@gmail.com>
>>>>
