s6-linux-utils is a set of minimalistic Linux-specific system utilities.
s6-linux-utils is free software. It is available under the ISC license.
git clone git://git.skarnet.org/s6-linux-utils
All these commands exit 111 if they encounter a temporary error, and 100 if they encounter a permanent error - such as a misuse. They exit 127 if they're trying to execute into a program and cannot find it, and 126 if they fail to execute into a program for another reason.
There are several good projects aiming to provide a minimal userspace environment for Linux, suitable for embedded systems. Among them, for instance:
Most of the time, these projects aim to implement standard commands in a lightweight way, and they do it well enough. So, although some standard reimplentation already exists in s6-linux-utils and its sibling package s6-portable-utils, it is an explicit non-goal of those packages to duplicate the work of those projects, and no more rewriting of standard commands will occur.