I have been a Software Engineer for 20 years. The vast majority of my work has been in the Unix and Linux environments. I have also been a deal of work using the Data General operating systems R-DOS, AOS, and AOS/VS, as well as a small amount of work using the MicroSoft environments. Systems Programming is my strong suit. Tool kits, language design, compiler writing, sockets programming and client/server systems make up just a part of what I have done.
Also, in the early 1980's I formed my own company, SuperUser Software, and did systems consulting and developed my own database management system. This system was called Dataman. It was a C-ISAM type of database whose commands were patterened after the verbs of the old Nixdorf programming language EDITOR. This package was sold to some clients at that time, and was in use for several years. In 2002 it was time for Dataman to come out of the stone age, and it was updated to be a fully multi-threaded database server. This server maintains the application source code compatibility of the original Dataman, while updating it to use the components of todays computing environment; Multiple local or remote network connections, database thread and record locking, user level protections, and more.
In the last very short while, I have taken up HTML and java programming. Admitedly, this website is very young, it was done with only about 4 hours of html study. But while the number of jobs for systems level engineers have been diminishing, this particular field still seems to still enjoy some robustness.