2012/12/16 Cheer Xiao <xiaqq...@gmail.com>:
> Hi Ray,
>
> I left a message on GTalk, but in case someone else is interested too:
>
> 2012/12/14 Ray <i...@maskray.me>:
>> Hi all,
>>
>> I'm a new fish user escaping from the zsh camp :)
>>
>> autojump is a productivity boost tool to chdir quickly
>> (https://github.com/joelthelion/autojump/wiki).
>>
>> j proj -> ~/to/long/dont/read/projects
>>
>> fasd absorbs autojump's idea and makes it convenient to reference file in a
>> similar manner on the command line.
>>
>> v often-accessed-file -> vim
>> ~/a/very/long/path/containing/an/often-accessed-file
>> o may-be-a-web-page -> xdg-open
>> ~/i/am/a/haskell/enthusiast/may-be-a-web-page
>>
>> I know that the chdir feature (initiated by autojump) can be worked around
>> by fish_prompt, however,
>> it seems difficult to emulate the file-reference feature (v
>> often-accessed-file) without some hooks.
>>
>
> Instead of hacking fish_prompt, you can bind a function to the event
> with the same name:
>
> function save_pwd --on-event fish_prompt
> ...
> end
>
>> As far as I know, fish does not have such preexec hook (zsh's preexec).
>> Have you considered adding such hooks or implement this functionality in
>> the core (it's very slow for fasd to use many awk scripts and others).
>
> Since you are already abusing the fish_prompt event, you can emulate
> preexec by peeking at $history[1] in a function bound to the
> fish_prompt event, which always contain the last executed command. The
> trigger for fish_prompt is roughly equivalent to that of precmd in
> zsh, and I think the difference between precmd and preexec doesn't
> make much difference here.
>
> Judging by zshmisc(1):
>
> preexec
> Executed just after a command has been read and is about
> to be exe‐
> cuted. If the history mechanism is active (and the
> line was not
> discarded from the history buffer), the string that the
> user typed
> is passed as the first argument, otherwise it is an
> empty string.
> The actual command that will be executed
> (including expanded
> aliases) is passed in two different forms: the second
> argument is a
> single-line, size-limited version of the command (with
> things like
> function bodies elided); the third argument contains the
> full text
> that is being executed.
>
> $history[1] seems pretty close.
>
After a little experimentation, it seems $history[1] doesn't do the trick:
xiaq ~> function --on-event fish_prompt foo
echo $history[1]
end
vim .xinitrc
xiaq ~> echo 1
1
function -e fish_prompt foo
echo $history[1]
end
xiaq ~> echo 2
2
echo 1
xiaq ~> echo 3
3
echo 2
xiaq ~> sleep 1
echo 3
Instead of the last executed command, $history[1] contains *last but
one* executed command. I doubted that this is related to the fact that
history saving is done in another thread in parallel with command
evaluation, so that there is chance that when fish_prompt gets called,
history saving is not yet finished. However, that doesn't seem to be
the case, as after a command that takes rather long (the last `sleep
1`), $history[1] is still the last but one executed command.
> However, I think preexec can be made much better if individual tokens
> (instead of whole command lines) are passed to the hook function, so
> that after defining foo like (supposing a "preexec" event is
> implemented in fish):
>
> function foo --on-event preexec
> ...
> end
>
> Typing a command "echo a b c" results in foo gets called with 3
> arguments, 'echo', 'a' and 'b' instead of 'echo a b' bundled together.
> Whether tokens are expanded before being passed still needs to be
> considered - typing "echo a{b,c}" might call foo with 'echo' and
> 'a{b,c}', or 'echo', 'ab' and 'ac'. I'm not sure which is more useful.
>
> One last little point - I think preexec is a pretty bad name. There is
> an exec builtin, and preexec might lead one to believe that it is
> called before exec is executed. (precmd is even worse; fish_prompt is
> way better that precmd.) I wish fish can use better names for similar
> functionalities.
--
Regards,
Cheer Xiao
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