Shell language and builtins

Strands Shell is Bourne-compatible: pipes, lists, loops, functions, subshells, and the expansions you reach for in a script all work. This page is the reference for the shell language itself and the builtins that back it, including where a construct diverges from Bash. For the external commands the shell ships (grep, curl, jq, and the rest), see the command inventory; for lua, see Lua scripting.

Shell language

Feature	Supported
Pipelines and lists	`\|`, `&&`, `\|\|`, `;`
Redirections	`>`, `>>`, `<`, `2>`, `&>`, here-docs `<<`
Conditionals	`if`, `elif`, `else`, `case`
Loops	`for`, `while`, `until`
Functions	definitions, `local` variables, `return`
Grouping	command groups `{ }`, subshells `( )`
Expansion	variables (`${VAR:-default}`, `${VAR%pat}`, `${#VAR}`), command substitution (`cmd`, `$(cmd)`), arithmetic `$(( ))`, globs
Quoting	single, double
Jobs	background `&`
Scripts	`. script.sh`, `source`

Builtins

Builtin	Notable gaps
`test`, `[`	No `[[ ]]`. Non-numeric or empty operands are treated as `0` (succeeds rather than erroring).
`printf`	No floating-point (`%f`, `%e`, `%g` print literally); `%d` does not parse `0x` or octal prefixes.
`read`	No `-a`, `-n`, or `-d`; a prefix `IFS=` is ignored; `-r` is effectively always on.
`set`	No `-o`, so `set -o pipefail` fails; only `e`, `u`, and `x` are supported.
`trap`	`EXIT` works; numeric signals (`trap ... 0`) are ignored; `-p` and `-l` are no-ops.
`alias`	Can be defined and listed, but aliases are never expanded during execution.
`readonly`	Enforced, but a violation returns exit 0; no `-p`.
`local`	Works within functions; silently succeeds when used outside a function.
`type`	No `-t` or `-a`.
`cd`	No `CDPATH`; `-P` and `-L` are not parsed.
`getopts`, `export`, `unset`, `shift`, `umask`, `hash`, `wait`, `:`	Full support.
`$(( ))` arithmetic	Precedence, bitwise, ternary, hex, and octal work correctly. Malformed input returns an incorrect result with exit 0 (`$((2 3))` yields `2`, `$((1/0))` yields `0`). Post-increment `x++`/`x--` returns the value without updating the variable.

Malformed numeric input never raises: test, [, and arithmetic $(( )) treat a non-numeric or empty operand as 0, so a typo in a comparison passes silently rather than erroring.