busybox VS coreutils

Also known as Dash in Debian (it's satandard POSIX shell) and sh in Busybox that sadly tainted the original BSD source file with GPL2.

https://github.com/mirror/busybox/blob/master/shell/ash.c

More Good projects to learn from:

  - Busybox (https://github.com/mirror/busybox)

Also, it's barebones POSIX, and not the Linux extensions you commonly think of. But, that means the processes are a lot simpler, and the code is often less complex. So it's a good place for a beginner to dip into to see how .e.g mv works, compared to GNU mv.

Sure... There are symlinks in the installation, and there's a small main() function that dispatches execution to the appropriate function based on argv[0], but that doesn't significantly impact the C implementation of each individual tool. Those seem pretty straightforward, to me. A developer reading.. e.g. chmod.c isn't going to see any evidence of symlinks, and minimal impact from the external main() function.

BusyBox: https://github.com/mirror/busybox/blob/master/coreutils/ls.c

true false

Ok here is my followup. I didn't go into detail about kea hooks [0] because I didn't write any kea hook before, but from what I can tell it should cover all your needs. You have to write c code which I find absurd tbh, but if it has the functionality you are looking for it could be a solution.

I already posted my dnsmasq "solution" so I will skip this. If you want a code example I could whip you one up.

Then there is coredhcp [1] and you can write plugins written in go for it.

From time to time some hobby dhcp server pop up, but most fade away since (I guess) the existing solutions are "good enough". I for instance implement a automatic provisioning and configurating dhcp setup with tftp and pxe boot using dnsmasq. It automatically creates pxe configs based on the mac address and some other stuff (tm). Kea seemed overkill for this usecase and I'm quite happy with what I got.

Your use case of automatically fixing hostnames through ISC seems a bit overkill to me as well to be frank. My home network has a few VLANs and every device in it is managed manually. It's a one time setup and most automation is unnecessary (and some devices in my network flatout ignore some dhcp options....). Aaaaanyway I still think that most dhcp servers out there support some form of scripting (heck even udhcpcd has a lease notify script that could be hacked to offer some of that functionality even though this gets only executed after the fact so a bit useless [2]).

> oh wait, I wonder how much ISC was paid … to do exactly this EOL … by these major ISPs?

I don't know. Nothing?

> Plausible future: I can envision a special DHCP vendor-specific OPTION to use time-based blockchain hash to further solidify their hold.

Reading your cynic banter I'm quite happy of not having your DHCP problems. Looking through your github repositories I can find a bunch of configuration files for dhclient, but not much in form of ISC configs (only the nintendo fix you posted in your first post). Would be really interested in your setup.

[0] https://kea.readthedocs.io/en/latest/arm/hooks.html

[1] https://github.com/coredhcp/coredhcp

[2] https://github.com/mirror/busybox/blob/master/examples/udhcp...

https://github.com/mirror/busybox/blob/121b02d6b6c9f276e7f8da560e5996d3e389cd63/networking/ntpd.c#L175

https://github.com/coreutils/coreutils/commit/fcfba90d0d27a1...

A summary of other changes just released in GNU coreutils 9.5 are:

* mv accepts --exchange to swap files

> some are simple like yes(1)

Not that simple: https://github.com/coreutils/coreutils/blob/master/src/yes.c

The -S / --split-string option[1] of /usr/bin/env is a relatively recent addition to GNU Coreutils. It's available starting from GNU Coreutils 8.30[2], released on 2018-07-01.

Beware of portability: it relies on a non-standard behavior from some operating systems. It only works for OS's that treat all the text after the first space as argument(s) to the shebanged executable; rather than just treating the whole string as an executable path (that can happen to contain spaces).

Fortunately this non-standard behavior is more the norm than the exception: it works at least on modern GNU/Linux, BSDs, and macOS.

[1] https://www.gnu.org/software/coreutils/manual/html_node/env-...

[2] https://github.com/coreutils/coreutils/blob/b09dc6306e7affaf...

> building a cat from scratch

> That would be an interesting project.

Here is the source code of the OpenBSD implementation of cat:

> https://github.com/openbsd/src/blob/master/bin/cat/cat.c

and here of the GNU coreutils implementation:

> https://github.com/coreutils/coreutils/blob/master/src/cat.c

Thus: I don't think building a cat from scratch or creating a tutorial about that topic is particularly hard (even though the HN audience would likely be interested in it). :-)

the yes command, writing to /dev/null, is making IO calls, which interfere with predictable scheduling.

If you look at the source code for yes, https://github.com/coreutils/coreutils/blob/master/src/yes.c

it builds a buffer of output and then writes that in a for loop

  while (full_write (STDOUT_FILENO, buf, bufused) == bufused)

Looking at the source of nohup, if the execvp() of the child happens then it _must_ have already done the signal (SIGHUP, SIG_IGN) so - WTF?

This got me wondering so I went and looked and it seems like lo and behold there was actually a commit to the GNU ls source just 2 weeks ago.

https://github.com/coreutils/coreutils/blob/master/src/ls.c

"maint: prefer char32_t to wchar_t"

even an empty file? Yes. so now it was a file with a copyright disclaimer and nothing else. And the koan-like question comes to mind is "Can you copyright nothing?" well AT&T sure tried.

Then somebody said our programs should be well defined and not depend on a fluke of unix, which at this point was probable a good idea. so it became "exit 0"

Then somebody said we should write our system utilities in C instead of shell so it runs faster. openbsd still has a good example of how this would look.

http://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/usr....

At some point gnu bureaucracy got involved and said all programs must support the '-h' flag. so that got added, then they said all programs must support locale so that got added. now days gnu true is an astonishing 80 lines long.

https://github.com/coreutils/coreutils/blob/master/src/true....

http://trillian.mit.edu/~jc/humor/ATT_Copyright_true.html

> Yes, ls is maintained. Although, maintained is a very strong word. It exists.

Why would it be a strong word? Here it is, in src/ls.c: https://github.com/coreutils/coreutils

It is then packaged by tens of operating system distributions, who themselves maintain extra patchsets, some of which are then upstreamed.

It is installed and used on millions (billions?) of devices, for 3 decades.

It's a very reliable and trusty "sharp stick of metal" :)