core utilities

Most systems (other than BSD based ones) use GNU's core utilities. It's used by most Linux distributions. Cygwin, MinGW and gnuwin32 run ported versions of the GNU applications as well. Even Microsoft's SFU/SUA included some of the GNU utilities. However, the GNU core utilities are typically more bloated and have more feature creep than other versions of standard Unix utility programs. BSD systems have their versions of core utilities. The latest version of Minix has adopted the BSD utilities. They tend to be less bloated than the GNU versions, but are still more bloated than other options out there. The BSD utilities also tend toward adding new features similar to but not to the same extent as the GNU utilities. Also, some of their utilities aren't as well optimized as the GNU versions. Busybox seems like the most viable option for a lightweight but still comprehensive version of core utilities. I'm currently using it on my Debian system instead of the GNU core utilities. Toybox is a similar alternative to Busybox. It has a better license option than Busybox, but it's lacking some features and tools that Busybox has.

Here are some links to core utility collections:

Earlier Minix alternatives
http://www.minix-vmd.org/cgi-bin/raw/source/std/1.7.5/src/commands/simple/
Earlier versions of Minix put together an interesting collection of lightweight utilities from various sources.

Busybox
https://busybox.net/
Windows ports of Busybox:
https://frippery.org/busybox/
https://github.com/rmyorston/busybox-w32
https://github.com/realthunder/busybox-w32

Toybox
http://landley.net/toybox/

Heirloom Project
http://heirloom.sourceforge.net/
Based on traditional implementations of standard Unix utilities. Not very portable to non-POSIX systems. Not as bloated as GNU or BSD core utilities.

OBase
https://github.com/chneukirchen/obase
Port of OpenBSD userland to Linux.

SBase
http://git.suckless.org/sbase
This started out as a discussion on one of the suckless.org mailing lists of how to write efficient core utilites that weren't all part of one executable like Busybox or Toybox. Some good examples were posted and the project was started. Then project development was quiet for a while. The project became active again and one of the main goals besides efficiency was UTF-8/internationalization support. Looks like they've borrowed some UTF-8 support concepts (such as Runes) from Plan 9. It's not designed to be portable to non-POSIX systems. However, it does look like they've covered replacing most of the basic core utilities with lightweight, efficient versions.

Other alternatives:
https://github.com/jbruchon/elks/tree/master/elkscmd
https://github.com/EtchedPixels/FUZIX/tree/master/Applications
https://github.com/Orc/bin
https://github.com/eltanin-os/utilchest
https://github.com/eltanin-os/cbase
https://github.com/rofl0r/hardcore-utils
http://git.musl-libc.org/cgit/noxcuse/tree/
https://github.com/pikhq/pikhq-coreutils
http://www.fefe.de/embutils/
http://skarnet.org/software/s6-portable-utils/
https://github.com/dimkr/lazy-utils
https://github.com/arsv/minitools
http://git.suckless.org/ubase
https://github.com/dcantrell/bsdutils
https://github.com/cheusov/nbase
https://github.com/rswier/swieros
https://github.com/minoca/swiss
https://github.com/mentos-team/MentOS/tree/master/programs

my core utilities

I've listed some core utilities options besides GNU. I thought I'd share something about what utilities I personally prefer to use. My main requirement in a good set of core utilities is portability. This is rather hard to find. You would think that if a utility was efficient and lightweight, it would be easy to port. However, that's not necessarily so. Many utilities that are designed for efficiency take advantage of features of a particular operating system which makes them harder to port.

At first, I considered starting with sbase which had stated goals similar to what I was looking for, but it didn't have enough features to effectively replace the GNU core utilities when developing and building programs. While newer versions of sbase have added a lot of functionality, they've become much less portable.

My favorite source for inspiration is Minix. Earlier versions provided some interesting and fairly portable versions of a variety of utilites:
https://www.minix-vmd.org/cgi-bin/raw/source/std/1.7.5/src/commands/simple/
Some of the utilities don't have sufficient UTF-8 support or lack some newer functionality found in GNU utilities that makes them fail when attempting to build applications. However, they make a useful starting point.

In some cases, the OBase or BSD utilities do a better job than the older Minix ones and still do that job efficiently. I particularly like the version of patch found on BSD systems. It's an earlier variant of the Free Software Foundation's patch program. Unlike the FSF's version of patch which uses the GNU license, it uses a BSD style license.

For some utilities, I've consulted the POSIX standards ( http://pubs.opengroup.org/onlinepubs/9699919799/idx/utilities.html ) and rewritten them from scratch.

Rather than trying to port utilities such as the Free Software Foundations coreutils, I thought having a lightweight, efficient, highly portable option would be a useful alternative. Many of the FSF developers have little interest in portability making it hard to get later versions of their programs working on non-POSIX systems. I was surprised at how little interest most users have in developing portable alternatives to the core utilities that could be used to build software. Not only was their little interest, some people posted extremely negative comments when anyone suggested creating alternatives to the FSF software. I was also surprised by some of the negative reactions I read about wonderful projects like SBase.

I have a growing collection of public domain, BSD and MIT licensed alternatives to the GNU core utilities. For now, I just use them for my own projects. If you have an interest in portable utilities and tools, would like to see a viable portable alternative to the FSF's GNU coreutils or would like to further discuss related topics in a positive light, feel free to contact me. I'd enjoy talking with other developers and utility users on the topic.

You'll find some added information on my utilities and information on how to discuss the topic further at:
http://www.distasis.com/cpp/lmbld.htm