Shell Programming and Scripting

I'm basically looking for the ksh equivalent of bash's PROMPT_COMMAND="history -r", where simply redrawing the command prompt in a terminal will cause ksh to reload the history file.

At the risk of sounding incredibly lazy (in which case I would be guilty as charged), I've noticed that if I have two terminals open--call them terminal A and terminal B--and run some commands in terminal A, I can only see those commands in terminal B (while scrolling up and down through the history) after I execute a command in terminal B. What I would like is for me to be able to just press enter at the command prompt in terminal B--without having to execute a command--and then be able to see the commands from terminal A.

Is there a setting in .kshrc that would force the shell to reload the history file each time the command prompt is drawn?

You might have better luck getting a reply from our ksh experts after the holidays.

Did you try searching the forums?

I did try searching, but no luck. I guess nobody using ksh as their interactive shell is as lazy as I am.

Hopefully one of the ksh experts will get back to me after holidays. In the meantime, I realized that ksh does not actually need to execute a command in order to reload the history file: While typing Enter by itself does not trigger a reload, typing anything (even just a semicolon) followed by Enter does.

So it seems that ksh's default behavior when it comes to the history file is "append then reload". My question for the experts is whether there is a command does "just reload". I've already looked at the ksh man page and snooped around for options to the fc command, no luck. If there is such a command, adding it to my prompt_commands function (see my "On korn shell, how to share history..." thread--apparently I'm still too new here to share the link) should do the trick.

Try:

Code:

alias r='fc -e -'

in ksh 88. I'm not quite sure what you meant by refresh, history -r is "recall" the way we used it, anyway. Using r alias:
r somecommand # recall a command, to edit the command you see, you need to have previously exported the EDITOR variable export EDITOR=vi Use the up arrow to scroll in reverse time order (from newest to oldest) from the point the r alias finds for you.

Code:

# start recall from last command issued.
r

Thank you, Jim, that is a useful alias but not what I'm looking for. I'll try to explain it differently:

When I'm working, I often have multiple terminal emulators open at once. If I pick any one of them and start pressing the up and down arrows, I don't see the commands recently run in the other open terminals. I'm looking for something to put in ~/.kshrc that will cause terminals to re-parse/reload my HISTFILE just by pressing Enter at a command prompt (without having to type anything at the prompt). This way, whenever I am jumping between terminals, when I pick a random one I can simply press Enter and then pressing the up and down arrows show me all the commands in my HISTFILE.

Hope that's more clear.

-- Post updated at 03:36 AM ---

Perhaps most succinctly: Is there a command that flushes korn shell's history buffer and replaces it with contents of HISTFILE?

I am not really sure what you mean by that, but first let us be precise: are you talking about ksh88 (as it is found as the default shell in AIX and HP-UX) or ksh93?

Second, as far as i know there is no "history buffer" - apart from the history file - in ksh. You can have a separate history file for each shell instance (actually i like it that way because usually i need in a certain session the commands i used there before again, not the ones i used elsewhere, but that is a matter of personal taste) or you can have all sessions share a common history file. In each case "history" in the Korn shell is what is in this history file, nothing more, nothing less.

I hope this helps.

bakunin

Hi, bakunin. I'm finding that it is not so simple. If I have ksh running in a terminal emulator and manually edit the history file while the emulator is running, lines that I add to the HISTFILE will be picked up by the emulator. However, lines that I delete from the HISTFILE continue to show up in the terminal emulator's history. So it seems that the shell's idea of the history (which I'm calling its "history buffer") and what's actually in the HISTFILE are two different things. The only way for deleted lines to stop showing is to close the terminal emulator and open a new one.

Maybe my terminal emulator is introducing some unexpected behavior? I'll try a different emulator.

Thank you Jim and Neo. Yes, I'm finding that the only way to understand exactly what's going on will be to look at the source code. Alas, while my sh/bash, python, and perl kung fu is strong, C/C++ looks like gibberish to me, but I'll give it a shot anyway. If switching terminal emulators and/or recompiling ksh don't give me exactly the behavior I want, I may just go back to bash, which feels much more comfortable.

P.S. I'm using the public domain korn shell v5.2.14 (the default shell in OpenBSD 6.4).