New paper: Word expansion supports POSIX shell interactivity

I’ve been thinking about and working on the POSIX shell for a little bit over a year now. I wrote a paper for OBT 2017, titled Understanding the POSIX Shell as a Programming Language, outlining why I think the shell is worthy of study.

For some time I’ve had the conviction that word expansion—the process that includes globbing with * but also things like command substitution with backticks—is somehow central to the shell’s interactivity. I’m pleased to have finally expressed my conviction in more detail: Word expansion supports POSIX shell interactivity will appear at PX 2018. Here’s the abstract:

The POSIX shell is the standard tool to deploy, control, and maintain systems of all kinds; the shell is used on a sliding scale from one-off commands in an interactive mode all the way to complex scripts managing, e.g., system boot sequences. For all of its utility, the POSIX shell is feared and maligned as a programming language: the shell is feared because of its incredible power, where a single command can destroy not just local but also remote systems; the shell is maligned because its semantics are non-standard, using word expansion where other languages would use evaluation.

I conjecture that word expansion is in fact an essential piece of the POSIX shell’s interactivity; word expansion is well adapted to the shell’s use cases and contributes critically to the shell’s interactive feel.

See you in Nice?