Why Doesn’t the POSIX Shell Standard Include Arrays?

The traditional shell model is centered on running commands, expanding text, handling files, and connecting programs through standard input and output. For those jobs, strings, positional parameters, and newline-delimited command output often cover the common cases. Arrays are useful, but they were not considered essential to the original shell design.

Mostly historical compatibility and minimalism. POSIX had to standardize behavior that existing Unix systems and shells already provided, rather than design a new shell from scratch. The Bourne shell, which became the basis for the standardized sh language, did not have an array data type, so adding one would have introduced compatibility and implementation concerns.

It’s also not accurate to say arrays have no place in automation—they can definitely make scripts safer and easier to structure. They simply were not part of the historical language that POSIX standardized. Shells such as Bash and KornShell later added arrays as extensions, but scripts that need strict POSIX portability generally use positional parameters or carefully managed text instead.