Shell Programming and Scripting

Well, pdksh is famous for being barely compatible with any real ksh, so i'd like to put what i said above in perspective: it was meant about "real" ksh-versions, mainly about ksh88 as found in AIX and ksh93 as found in AIX and Linux. The (real, AST) Korn shell was made open source IIRC 2005, so there is IMHO no reason to work with rather inept look-alikes (or, rather, look-similars) like the pdksh at all. Drop it and get a real Korn shell from github or kornshell.com.

I hope this helps.

bakunin

I recommend you open the C/C++ source code in a modern code editor, and having said that, I strongly recommend Visual Studio Code with the CPP extension:

C++ programming with Visual Studio Code

VSC also has extensions to prettify (format, beautify), indent, and to color matching brackets, braces and parens so all of this "cool stuff" makes code easier to read (and colorful, LOL)

Having the IntelliSense for CPP will help you understand the code. I write mostly in Javascript, PHP, CSS and HTML these days (nearly every day). VSC saves me a lot of time debugging syntax and keeping things moving along in a brisk development pace.

Got it. Do not put a leading dot on the history file name, which means you have to declare HISTFILE. (ksh93). This lets you get buffering and then writing to the history file without erasing the contents. As an aside a lot of command C code evaluates environment variables. It may also set some.
Try:

Code:

strings/usr/bin/ksh | egrep '(HIST|FILE|SIZ)'

Then try dinking around with some of the variables. If the shell you use will not get updated like bash does, this can be one way to get custom behaviors.
Alternatively, if you can read C, consider spending some time read the source code for ksh93 if that is your shell. The code is now on github.
See: Building ksh from Source Code (Learning the Korn Shell, 2nd Edition)

This is immensely important for technical people who are pushing the envelope or working on custom behaviors.

It's always best to go to the source code, when available, to understand what is going on under-the-hood and to add custom code.

Arguably, reading C or C++ code is a lot more difficult than reading PHP or Javascript or Python or C#, etc. at least for me, I find C or C++ is too down-in-the-weeds to easily grasp the functionality of the code.

I spend a lot of time coding, I mean a LOT Of time coding, and at least for me, writing code is a kind of digital artistic poetry, where bug hunting makes me smile and odd behavioral issues turn me into a kind of Sherlock Holmes for code.

Side story:

I was in truck riding along in the mountains with a US-born web developer turned real-estate agent recently. We were talking about coding and he told me he often slams the keyboard down or yells at his computer when coding and doing IT. He looked at me for affirmation of his frustration. I told in in reply that I mostly get joy from IT and coding, and often find myself smiling when bug hunting and when things do not go as expected. In fact, I told him that I find it hard to have any emotions when coding and problem solving, except for joy, and when I wake up in the morning, I am really excited to have that cup of java and login and code solutions my mind figured out when I was asleep.

Sometimes even here, I see people getting emotional over something (recently a moderator threatened to quit because they don't like some of my code changes and the transitions I am working on here). I am surprised by this and this has led to be believe I've been working in IT for so long, that writing code brings me truly great joy. Negative emotions are not really useful and so I don't have them over anything. However, I see a lot of IT people carry around with them a lot of frustration and anger and emotions related to IT and technology (mostly the middle aged and much older IT people, not the younger generation).

Anyway, I'm well off topic.

My point is that IT is a joy, coding is not some "geeky thing for losers" but it is a blessing and a great way to use your mind. Jim was right on to suggest looking at the ksh source for DevuanFan's custom ideas; and I hope DevuanFan will read the source and post back the code, the details he learned and his proposed solution

If you are in IT and do not love to code, search code, read code, write code, you are in the wrong business or hobby!

Thanks, bakunin. I'm new to the Korn shell, so had no idea about these nuances. I see that ksh93 is in the OpenBSD package repository, so I'll install it and see how it's different from pdksh.

Neo, I will give VSC/IntelliSense a try. If it makes CPP easier to read and work with, I will probably really like it.

In the meantime, I'm back to bash for when I want to work and not play/explore. I find that having this in my .bashrc gives me exactly the behavior I expect (namely, any time I press Enter in a terminal, the shell's idea of the history matches exactly what is in my HISTFILE--no more, no less):

Code:

PROMPT_COMMAND="history -a; history -c; history -r"

Thank you all very much. Happy hacking!

OK, i might be a bit slow but now i get what you want. If this is what you want you can have that in ksh too. There is no PROMPT_COMMAND variable in ksh but the shell prompt itself is capable of executing commands:

Code:

PS1='$(command; command; command; ...) <rest of your prompt here>'

Notice that editing the commad history needs the variable HISTEDIT (in ksh93) or FCEDIT (in ksh88) to be set to your preferred editor, otherwise you end up in ed. The history comamnd in ksh is hist, which by default is aliased to fc and r (for "repeat"). You can search and replace when repeating commands like this:

Code:

r old=new x

which will re-run the last command line starting with "x" but the instances of "old" replaced with "new".

I hope this helps.

bakunin

I had tried that, but apparently pdksh there is no history command: 'history' is just an alias for 'fc -l'

So you're saying the "real" ksh has 'history' command with these flags? Nice! I'm sorry about the ksh version mixup. It's tough being a noob!