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(First posting to Plänet Commandline! Tag: pcli)

Vutral asked in IRC how to synchronise two shells’ environment while they’re running. As you may know, POSIX systems cannot change a process’ environment vector after it has been started, only the process itself can. Well, the shell can, and we’ll use a variety of things for this.

This trick assumes you have $HISTFILE set to the same pathname in both shells (obviously, they run under the same user). It uses export -p to render the current list of exported variables, then transforms the list from newline-separated to a single big one-line export statement.
Then it transforms all remaining newlines (which will be part of a single-quoted string, since that’s mksh(1)’s export format) into the sequence '$'\n'' which means: terminate current single-quoted string, append $'\n' and open up a new single-quoted string immediately; concatenate these three.
Now, $'\n' is just a fancy way of saying newline, and part of mksh because David Korn (yes, the Korn in Korn Shell) strongly suggested to me that this functionality be included – but, as we can see here, it pays off.
Finally, the so transformed string is prepended by unset \$(export); which, when executed, will cause the shell to unset (and unexport) all currently exported variables. The shell parameters that are not exported, i.e. not in the environment, are not affected by this code (except for $x and $nl, but… whatever).
This string is then passed to read -s (plus -r and clearing IFS to enable raw mode), which means, read into the parameter $REPLY (which we conveniently don’t use – but it’s trashed too, thus) but store into history at the same time.

Ah hah! Now, the persistent history feature comes into effect! After running the below statement in the “source” shell, switch into the terminal running the “destination” shell, press Enter once on the empty line (Ctrl-U to empty it if it wasn’t), then Cursor-Up (↑) to recall… voilà, an insanely large line with the previously created string sorta expanded… and press Enter again to run it. Now your set of exported parameters is the exact same (minus if you exported IFS, nl, x or REPLY) as in the “source” shell.

I’ve added extra spaces and a linewrap below, this is really just one big line:

nl=$'\n'; x=$(export -p); x=${x//${nl}export/}; IFS= read -rs <<<"unset \\\$(export);${x//$nl/\'\$\'\\\\n\'\'}"

Of course, this makes a nice function, for your ~/.mkshrc or somesuch.

mksh-current has just gained an experimental recursive parser for command substitutions, fixing RedHat BZ#496791 and decades-old complaints about the pdksh codebase, compared to AT&T ksh93. (GNU bash could also do the example, but not some other things mksh(1) parses fine now.)

This means that things like the following work now.

	# POSIX, should “always” work
	echo $(case 1 in (1) echo yes;; (2) echo no;; esac)
	# POSIX optional, works now in mksh, works in GNU bash
	echo $(case 1 in 1) echo yes;; 2) echo no;; esac)
	# GNU bash seems to choke on comments ending with backslash
	# a comment with " ' \
	echo yes
	# a comment with " ' \
	# No non-recursive COMSUB parser can pass all of the above
	# tests and these below at the same time (some extensions)
	echo $(typeset -i10 x=16#20; echo $x)
	echo $(typeset -Uui16 x=16#$(id -u)
	) .
	echo $(c=1; d=1
	typeset -Uui16 a=36#foo; c=2
	typeset -Uui16 b=36 #foo; d=2
	echo $a $b $c $d)
	# the ‘#’ is especially tricky, that’s why the above cases

Next on my TODO is the complete rewrite of the read built-in command, as well as its documentation. I think that the (reduced) goals for mksh R40 will have been met by then, except porting to LynxOS and MPE, but we’re working on it, and re-testing Syllable and Plan 9). Of course, a release implies testing on a lot of the supposedly supported platforms, so it won’t be out “immediately”. Though, associative arrays have been removed from the R40 goals, so that I can at least get a new release out. Note that Debian and OpenSuSE Buildservice users have been provided with somewhat well-tested mksh-current snapshots for a while already, and Gentoo users can use the “live ebuild”; there’s always compiling from source too…

(Free)BSD vs. Linux

03.03.2011 by tg@
Tags: debian event ill mksh rant

Warning: this is a rant against BSD (specifically FreeBSD®, but don’t let me get started on DragonFly, who think it’s wise to drop all shells except ash from the base system and rely on pkgsrc® – yay let’s compile a dozen packages just to get a shell with tab completion, not to mention boxen with no network access – for the task – although others seem to go into that direction too…; you know, there’s BSD, and then there’s FreeBSD…) – don’t like, don’t read.

If you want to change something in the BSD world, you gotta fork your own BSD – no other way around the thickheads. Ok, back then, I ran into a particularily thick one, but others tend to not be much better. Users share the thickness. If you want to change something in the GNU/Linux world, just make a package, have someone upload it, prod (or pay, Hanno got a Radler) people to do it, or just upload it yourself.

At the BSD booth at FOSDEM, despite me bringing the Windows® Mobile 6 Professional devive, strictly for Geocaching mind you, Macintosh boxen had a share of more than 50% – I didn’t manage to tip the scale. At the Debian booth, almost everyone had a “I want to buy a new laptop some day, but it just keeps on working and doesn’t break” pre-Lenovo IBM laptop. No hyping of Google either. (Last year’s CLT saw BSD people advocating pro-Schily – the guy with the broken encoding in his name – shockingly.)

Honestly, tcsh, FreeBSD® people? Sorry. While I agree that there is merit on having the same script and interactive shell, as someone has pointed out (copy-paste examples into the command line), there’s those zsh users who use mksh or GNU bash for scripting. Or just POSIX shell. And that’s with an interactive shell which can be used for scripting. On the other hand, the C shell (both csh and tcsh) cannot.

And what’s with pretending the accent gravis is non-combining, called “backtick” (such a thing does not exist); and advocating it? Sorry, if your csh/tcsh doesn’t handle the POSIX $(…) you should just drop it. (By the way, there is a convention that example command lines are prefixed with for csh and for sh (or but we write $ sudo  instead, these days). Use it. Or leave it. If you have examples that substitute another process’ output, be specific.) It’s funny to see how one person tries to defuse my arguments against csh by telling me “it’s just an interactive shell”, while the other argues that people copy-paste between them, to which that was my response. Read the thread!

And please, get your facts right. “I would prefer that the standard shell be at least Bourne-compatible.” You don’t want Bourne (“^” instead of “|” for pipes), you want POSIX. That GNU bash is called the Bourne-Again Shell in one of their usual semi-bad puns doesn’t help the global perception of such things any. Also, the root shell and /bin/sh are disjunct.

(Plus, why change the root shell, use sudo(8), plain and simple.)

ObNote: in jupp (should I package that for Debian, btw? rather upload, packages are ready…) the ‘`’ key is used as præfix for Ctrl-X (`X) or to directly enter numerical (decimal, octal, sedecimal/hexadecadic) ASCII, 8-bit or Unicode codepoints. Yay!
And even the FSF has seen the light; for a few releases already, GCC uses “'…'” instead of “`…'” for quoting in messages, even without locales. Great job there! (LC_MESSAGES=en_GB.UTF-8 usually works, too, though.)

ObDisclaimer: I have an (yes, Google…) Alert on the word “mksh”, so I know when it’s being discussed. This obviously includes certain fora. Also, I’m a shell implementer and bound to know a certain amount of details. Plus, mksh’s build script runs with pretty much any Bourne/POSIX/Z Shell which has functions and not too many bugs. I wrote it. Go figure. No lowly trolling.

FWIW, mksh(1) has the cat(1) builtin both because Android has no cat(1), and as speed hack. Almost all other shells have worse speed hacks, like a printf(1) builtin. And recently, builtins have become direct-callable, so this actually reduces the overall system footprint. (Its inclusion also provides for some other possibilities, internally.) And as two final side notes, if you haven’t seen this: determine which shell we are run under (CVS) and I still offer a prompt conversion service (send me any GNU bash or oksh $PS1 and I’ll send that to you in mksh(1) syntax – optionally with adjustments/improvements, like cwd uses only up to 1/3 of screen width).

Eh. Why does mksh built with (a patched: mkstemp(3) added) klibc work suddenly, unexpectedly?

To reproduce, I just uploaded mksh_39.3.20110218-1.dsc and you can run DEB_BUILD_OPTIONS=mksh-static=klibc,dietlibc,eglibc dpkg-buildpackage -rfakeroot to verify it, once you have mkstemp(3). (I will probably send a smaller implementation of that in, later.) I have that and the open fix and the m68k patch applied, nothing else… where did my bug go?

ObQuestion: what’s the legal (copyright/trademark) status of the Atari logo (the one in rainbow colours, with three things going up, right and left “leg” looking like an umbrella stand’s)?

FOSDEM was a blast!

13.02.2011 by tg@

I just need to work more on bilocality. While I did find two geocaches, one at the South/Noon Train Station (taalverwarringen…), one in the buurt of the University, I did manage to miss the AW building completely and utterly. Wow. Except, that Haiku guy came over to talk for a bit (nice). And I drew. An Atari logo with swirl, for that weird stuff I recently have been found doing.

More mksh-current news coming soon, stay tuned. In the meanwhile, I met bonsaikitten IRL (at FOSDEM, yes, too) who kindly made a “live ebuild”, i.e. a source package building -current.

Finally let’s say a big thank you to the person mostly manning our booth, gecko2, and to Benny for talking to people, getting That Other Packaging Thingy working, and pimping the website a bit.

mksh wins

28.01.2011 by tg@
Tags: debian mksh

The Android 3.0 (Honeycomb) Preview [German news] comes with a much more sensible /system/bin/sh than previous released versions… Android-x86 and AOSP have had it for a while, but this sees the general adoption of mksh(1) as the only POSIX/Korn Shell on the Android OS! Thanks to those who helped to make this reality.

I’ve just prepared an ISO for FOSDEM Ⅺ which we might export on BitTorrent soon. Benny has provided an upgraded desktop background image, thanks.

The next mksh release… well I’ll bite the sour apple and will release it without associative arrays but hope I get around to hack a few things (especially the read and sleep builtins) before releasing. One lession learned, don’t brag with oh-so-big plans when you haven’t got a deliverable yet. Real Life will interfere. Oh, and Murphy, of course. (mksh R41 might have the associative arrays then. But mksh-current has ${foo@#} which is hash($foo).

FOSDEM, the Free and Open Source Software Developers' European Meeting

❧ Who’s not? ☺ Same procedure as every year.

(okay, lolando prefers skiïng but…)

Anyway. A cow‐orker told me that Belgium again/still has no gouvernment, and they have been asked to grow out their beards until they do. I found “evidence” on the ’net but won’t link it here, also it’s on German… anyway. Let’s all join in. (Besides, I now have an excuse to not shave, maybe even my grandmother will accept this one…)

RT said on IRC that mksh will probably work on MSYS.

My Debian/m68k stuff is coming around nicely, but I still haven’t gotten around to do everything planned, plus I need to grow a new kernel and eglibc, after the latest uploads, and the 2.6.37 based one panics. Also I’ve got to take care to not overwork myself. (And make a MirBSD ISO for FOSDEM.) But hey, it’s been not working for some time and better now. And slow anyway ☺ yet we’re progressing. Does anyone know how to debug that a C programme only calling res_init(3) segfaults?

Benny is apparently not just working on making NetBSD® pkgsrc® available on MirOS BSD (picking up my work from 4+ years ago) but also replacing The MirPorts Framework with it. Sad, as I got a request for a gajim MirPort over a cocktail just this evening…

I’m almost finished with “sort of re-bootstrapping” Debian/m68k (I can use etch-m68k as well as what was in unstable at the moment as dependencies, so it was not that much, still, 305 binary packages build from 84 source packages, most for unstable (very few for unreleased, with very responsive maintainers, thanks all, who will include the patches in their next uploads) is a bit… including rebuilds with newer versions, more patches, more testing or newer dependencies installed. I’ll probably upload on Sunday evening, as I’ll be off for 2-4 days at least from then (see below). Ingo tried to test on real hardware, but as Murphy wants a hard disc failed… we’ll still try to get something done over the weekend. If you want to have a look, see my repository index (sources.txt contains a sample sources.list file, 0-NOTE.txt some hints, including the right debootstrap/cowbuilder magic and speed tricks). I’ll need to learn how to use LVM and set up a buildd now…

I’ve not been in much of a hacking mood recently – all these visits to the dentist leave me in unrest and disturb my equilibrium. Hence, not much activity even in mksh even if there was need, almost none in MirBSD. This is only temporary, but I won’t attend OpenRheinRuhr, or, if I come at all, it’ll be for socialising only and probably only one day. Benny’s done with his Doctor (in France, no idea whether it’s one in Germany as well) of Chemistry and has returned to hacking some (World of) Google-Go(o) code. I expect MirBSD activity to slowly raise once we can come back. Please accept our apologies.

mksh, encodings, MirBSD, BitTorrent, WinCE

28.08.2010 by tg@
Tags: android debian geocache hardware mksh news release snapshot

mksh was merged into Android (both AOSP and Google’s internal master tree) in the night 24/25th August, and is expected to be the one shell to rule them all, for Gingerbread.

mksh(1) now also has a cat builtin, for here documents mostly. It calls the cat(1) command if it receives any options. The shell is nevertheless smaller than yesterday because of improved string pooling.

There’s another reason to use the MirOS OPTU-16 encoding instead of PEP 383, on which I already wrote: try passing a wide-char filename to a function such as MessageBoxW, or create a filename on a system using wide chars, such as FAT’s LFN or ISO 9660’s Joliet, or one that only allows Unicode (canonically decomposed – ü → ü – out of all things) like HFS+. OPTU-8 at least maps to somewhat reserved codepoints (would, of course, be better to get an official 128 codepoint block, but the chance’s small of getting that in the BMP). Still.

Oh well, the torrents. I’ve remade them all, using one DHT seed node and OpenBitTorrent as tracker and put them on a very rudimentary BT page that will be completely redone soonish. Please re-download them. I currently do not believe will return.

Finally, I fell victim to a selling-out and may have just bought a Windows Mobile 6 based phone (Glofiish X650) and an SDHC card and an extra battery with double capacity. Well, at least it’s said to run CacheWolf well. I still would like to have something like Interix, Cygwin, UWIN, coLinux, or maybe some qemu-for-WinCE variant that runs Android, Maemo, Debian/armhf (or armel or arm) at near-native speed (and is usable – the device sadly doesn’t have a hardware keyboard, but it comes with SiRFstar Ⅲ GPSr). It only has 64 MiB RAM, like the Zaurus SL-C3200 and the jesusPhone, though. ☹ Any chance to get MirWorldDomination onto that device as well?

Tomorrow, eight years ago, is the date we now use as birthing point for MirOS. The thing is, we did not really want to create a BSD of our own, fork, or whatnot. We were mostly happy OpenBSD users (really happy before the first eMail exchange with its developers, where Theo de Raadt did indeed stand out but was not the only one – just the one with the authority to deny us), improved it locally and submitted patches and ports. We were flamed for that or, worse, ignored. I begun putting up my “OpenBSD patchkit” on my homepage (back then, at Tripod) and still tried to feed things to upstream and OpenBSD. Then, at some point, Theo de Raadt made it clear he did not want me and the patch kit had grown (from one 4M file into several of them), so I ended up doing a “cvs -d /cvs init” and went from there. Benny’s story is similar – he laughed at me while trying to get ports added to OpenBSD, then discovered his ports were added to the MirPorts Framework and getting commit access there was easier than getting some random developer to commit something of his to OpenBSD. (This trend ended there though… every single person I approached since has become OpenBSD ports committer – I wonder whether they used my invitation letter to blackmail Theo?) It’s often thought that there was a clash of opinions between Theo and me. I think while we might disagree in certain aspects or priorities things should have, in the end we both wanted the same thing, I just was promised to never become a member of the OpenBSD project, so it’s really just “them” being uncooperative. (They (Henning and others) did burn the T-Shirt I gave Theo as a gift some day for making OpenBSD what it was. I won’t comment on that, again, now.)

FrOSCon was a blast. I had two booths of my own – MirBSD and FreeWRT – as well as shares of Debian and Grml. Well, MirBSD was run by Benny and gecko2 because I just didn’t have any time for it, despite XTaran’s help with the FreeWRT booth. All I did was the initial setup of both booths, while at the same time answering about three questions regarding FreeWRT in parallel. Wow. What a little small, open hardware can do to you. XTaran and I had fun and we’ll do FreeWRT booths again; I managed to flash my two FON2100 devices (“La Fonera” – the FON2200 can use the same image, says nbd of OpenWrt) and will fix the port’s remaining few bugs I found; XTaran will try to push the WL-500gPv2 development. The social part was nice as well, although I think the greek restaurant in the city will not be visited by me again. Anyway, if you didn’t attend FrOSCon, your own fault…

Since the BitTorrent tracker used by MirOS is down, here’s the link to the [updated 2010-08-28] [deleted 2014-05013] current (FrOSCon 2010 Edition) snapshot’s torrent, Triforce as usual. We’ll probably rewrite torrent files for all our ISOs and publish them on the MirBSD website. I’m currently considering OpenBitTorrent plus one or two DHT seed nodes with no statistics. Maybe with webseed. (Need to update the libtorrent/rtorrent MirPorts first, though…) Other options would be different trackers or running one of our own. I will announce the outcome as news entry, once done.

On the plus side, the review process of mksh(1) in Android continues, and I fixed the realpath builtin to behave even more POSIX-ish.

Well, I suppose I should be happy that mksh is actually used…

  • [tg] Correct shf buffer I/O routines to avoid a memory corruption bug discovered by Waldemar Brodkorb and other bad effects
  • [tg] Fix NULL pointer dereference during iteration loop when checking for alias recursion; discovered by Michal Hlavinka

That’s OpenADK (Waldemar’s fork of FreeWRT, which is Waldemar’s fork of OpenWrt), and Red Hat Enterprise Linux, respectively. Popcon in Debian and its derivates is also pleasant.

I could use some help bugfixing this though:

	(sleep 3; exit 12) &
	sleep 6
	# background process is done by now
	wait $bgprocpid
	# POSIX mandates that, since $! was asked
	# for, wait is to reply its errorlevel

Somehow, JF_KNOWN is never set – and I can’t debug this with gdb(1).

(There’s also a dashism in some *buntu start scripts that does pretty much the same except it uses “wait %1” there. In fact it doesn’t even seem to use $! – no idea whether we can support that at all in a POSIX shell – which dash clearly isn’t… – without keeping track of background processes forever.)

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