John Snow <js...@redhat.com> writes:
> 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...!)
Hah! Saving it would be easy enough, but reloading it... okay, call it
a "backup" and declare victory when saving works.
>>>>>>
>>>>>> 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.
For what it's worth, bash defaults HISTSIZE to 500.
GNU Readline lets users configure it in ~/.inputrc. Conditional
configuration is possible, i.e. something like
$if Qmp-shell
set history-size 5000
$endif
should work, provided qmp-shell sets rl_readline_name as it should.
>>>>>> + 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>
>>>>>
