Ticket #3748 (new enhancement)

Opened 8 years ago

Last modified 11 days ago

mksh as a subshell

Reported by: gloomyquazar Owned by:
Priority: minor Milestone: 4.8.33
Component: mc-core Version: master
Keywords: subshell mksh Cc:
Blocked By: #3692 Blocking:
Branch state: no branch Votes for changeset:

Description

Hello.

On my desktop and notebook I use FreeBSD together with mksh, which I like for it's small size, robustness, security... Recently I got to know that MC supports only bash, (t)csh, zsh and something else as main shells, hence my mksh doesn't work as a subshell, I can't just switch with Ctrl+O and work there, so I had to postpone using MC for now. Is there a way to add mksh for supported shells? Without a subshell working in MC gets very unconvenient.

With regards,
Sergey P.

Attachments

mc-mksh-subshell.patch (2.8 KB) - added by gloomyquazar 8 years ago.
mc-mksh-subshell-v2.patch (2.8 KB) - added by gloomyquazar 8 years ago.

Change History

comment:1 follow-up: ↓ 2 Changed 8 years ago by gloomyquazar

It would be nice to also add support for general Bourne /bin/sh as a subshell.

comment:2 in reply to: ↑ 1 Changed 8 years ago by andrew_b

  • Blocked By 3692 added
  • Milestone changed from 4.8.19 to Future Releases

Replying to gloomyquazar:

It would be nice to also add support for general Bourne /bin/sh as a subshell.

#3658

comment:3 Changed 8 years ago by zaytsev

If mksh has an equivalent of precmd (which, I think, it does) and you can cook up a patch to support it that is not impossible.

comment:4 Changed 8 years ago by gloomyquazar

Maybe the function like this will do?

function precmd {

<put something here>

}

PS1="$(precmd) $PS1 "

comment:5 Changed 8 years ago by zaytsev

As I said, if you manage to provide a clean working patch, we might eventually get it in.

Changed 8 years ago by gloomyquazar

comment:6 Changed 8 years ago by gloomyquazar

Could you please check this patch? It works OK for me.

Changed 8 years ago by gloomyquazar

comment:7 Changed 7 years ago by woodsb02

Any progress on this?
The v2 patch looks simple enough.

Last edited 7 years ago by woodsb02 (previous) (diff)

comment:8 follow-up: ↓ 9 Changed 4 weeks ago by zaytsev

comment:9 in reply to: ↑ 8 Changed 4 weeks ago by d3m3t3r

Replying to zaytsev:

Somebody turned this in a PR:

https://github.com/MidnightCommander/mc/pull/209

Added support for ksh/oksh/mksh Korn shell variants.

comment:10 Changed 4 weeks ago by zaytsev

  • Milestone changed from Future Releases to 4.8.33

I assume you tested it and it works for you?

  • I'm surprised that the "precmd" part was so simple. Is that due to static prompt? Is supporting user prompt impossible / problematic?
  • I'm not sure that ksh supports HISTCONTROL... Does it really? If yes, good news.

comment:11 Changed 4 weeks ago by d3m3t3r

I need to fix it for mksh which is actually dumber than other pdksh/openbsd based variants. mksh doesn't support HISTCONTROL either \x placeholders in PS1 and recognizes not just ENV but $HOME/.mkshrc too.

Couldn't find any "precmd" like functionality in any variant so I suppose user prompt is not possible.

Since mksh seems to be quite different from other variants, would you recommend using distinct SHELL_KSH and SHELL_MKSH types? Or perhaps use single SHELL_KSH type but specific mc_shell->name?

comment:12 Changed 4 weeks ago by zaytsev

Since mksh seems to be quite different from other variants

I would add SHELL_MKSH if it's different enough, and SHELL_OKSH / SHELL_PDKSH (whichever official names make sense, didn't look into it) for clarity - you can use multiple enum values for the same case.

Couldn't find any "precmd" like functionality in any variant so I suppose user prompt is not possible.

It would be great to have this as a comment. Otherwise our children will wonder...

mksh doesn't support HISTCONTROL

But the others do, or everything is trashed with our cd commands?

comment:13 Changed 4 weeks ago by d3m3t3r

First, thanks much for the feedback. I've split mksh support under its own SHELL_MKSH type since its features differ so much it makes sense to handle it separately.

Some overview: There seems to be several implementations of ksh around but all but mksh (MirBSD ksh https://github.com/MirBSD/mksh) are based on pdksh (Public Domain ksh), in particular ports of OpenBSD ksh, e.g. https://github.com/dimkr/loksh and https://github.com/ibara/oksh. pdksh supports \x codes, variable and command substitution in PS1, HISTCONTROL (ignorespace & ignoredups) and ENV variable for interactive shell rc-file. mksh, on the other hand, doesn't support \x codes in PS1 either HISTCONTROL. It supports ENV variable for interactive shell rc-file but if it's not set the shell also tries ~/.mkshrc.

comment:14 Changed 4 weeks ago by d3m3t3r

  • Cc d3m3t3r@… added

comment:15 Changed 2 weeks ago by d3m3t3r

  • Cc d3m3t3r@… removed

comment:16 Changed 2 weeks ago by zaytsev

Sorry, I still don't have time to look into it deeper... but I wonder, can actually the plain POSIX sh be supported with the fallback? Maybe you have the answer since you looked deeper into it.

comment:17 Changed 12 days ago by d3m3t3r

but I wonder, can actually the plain POSIX sh be supported with the fallback? Maybe you have the answer since you looked deeper into it.

I don't think the precmd fallback emulation in mc supports the plain POSIX shell because it relies on the command substitution in PS1 which according to the specification (https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_05_03) is unspecified.

comment:18 Changed 11 days ago by d3m3t3r

There's summary of the changes in my PR:

  1. Add support for mksh - uses fallback precmd emulation.
  2. Add support for pdksh-based ksh (e.g. OpenBSD's ksh) - supports user prompt.
  3. Enhance fallback precmd emulation to support user prompt (affect ash/dash/mksh).

I tested on Alpine Linux with busybox, dash, mksh, oksh (OpenBSD's ksh port) and loksh (another OpenBSD's ksh port) packages.

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