history sharing between ttys

history sharing between ttys

[Herb Maeder]

While we are on the subject of history...  I seem to remember from using a
version of ksh way back when, that it was possible to set it up so that you
can share history between multiple ttys.  So if I typed a command in one
window, I could retrieve and execute it from another window.  

I imagine there is some overhead for doing this, since I believe that it was
just done by maintaining one common history file that was updated after each
command.  But it was really quite useful since it reduces the need to cut
and paste and is especially useful for retrieving those long, interesting
commands when you log on from a different machine. 

Is it currently possible to do something like this in zsh?  If not, are
there plans to support it in the future?

Herb.

Re: history sharing between ttys

[Steve Reid]

> While we are on the subject of history...  I seem to remember from using a
> version of ksh way back when, that it was possible to set it up so that you
> can share history between multiple ttys.  So if I typed a command in one
> window, I could retrieve and execute it from another window.  

Something like this? Last time I tried it (zsh 3.0.2) it didn't work
correctly... I was told that it was because of a bug in the new history
code.

precmd() {
	fc -AI ~$USER/.history;	# Append latest commands
	fc -R ~$USER/.history;	# Read changes from all zsh's
}                                         

I remember using the bash equivalent before I switched to zsh. The only
problem was that it doesn't update the history until after the command
exits, so commands aren't always saved in the correct order.

Ideally, it should be possible to append the command to the history
file immediately after the command is entered. Other running zsh's
should detect the change and read it, so the user doesn't have to hit
enter every time they switch ttys.

Wishlist:
 setopt synchronize_histories

Re: history sharing between ttys

[Bart Schaefer]

On Feb 13,  5:26pm, Steve Reid wrote:
} Subject: Re: history sharing between ttys
}
} > [...] set it up so that you
} > can share history between multiple ttys.  So if I typed a command in one
} > window, I could retrieve and execute it from another window.  
} 
} Something like this? Last time I tried it (zsh 3.0.2) it didn't work
} correctly... I was told that it was because of a bug in the new history
} code.
} 
} precmd() {
} 	fc -AI ~$USER/.history;	# Append latest commands
} 	fc -R ~$USER/.history;	# Read changes from all zsh's
} }                                         

This appears to work fine in zsh 3.0.3-test4 (although I have applied a
couple of other patches, I don't think any of them would affect this).

However, the behavior is a little strange, because you immediately read
back not only everything the other shell wrote, but also everything you
just wrote, which causes the event numbers to jump by large increments at
every command.  The following seems to work a bit better; the event number
jumps only when some other zsh has actually written the file:

    precmd() {
	if [[ ~/.history -nt ~/.history-$HOST-$$ ]]
	then
	    fc -AI ~/.history
	    fc -R ~/.history
	else
	    fc -AI ~/.history
	fi
	<~/.history >| ~/.history-$HOST-$$
    }

} Ideally, it should be possible to append the command to the history
} file immediately after the command is entered.

Write a zsh 3.1 module that fronts for the `accept-line' ZLE action ...

} Other running zsh's
} should detect the change and read it, so the user doesn't have to hit
} enter every time they switch ttys.

That's almost doable:	TMOUT=10 ; trap precmd ALRM

-- 
Bart Schaefer                             Brass Lantern Enterprises
http://www.well.com/user/barts            http://www.nbn.com/people/lantern