Language Compatibility Inventory

CJSH is a POSIX-focused shell with selected Bash and Zsh conveniences. It does not claim formal POSIX certification, complete Bash compatibility, or complete Zsh compatibility. This inventory is the source of truth for the extensions that are intentionally supported.

Current support

Area	Status	CJSH behavior
Portable shell syntax	Broad support	Functions, pipelines, redirections, substitutions, control flow, traps, job control, and the standard parameter operators are covered by the shell test suite. --posix disables or rejects CJSH extensions where practical.
Indexed arrays	Supported extension	declare -a, indexed assignment, ${array[index]}, ${array[@]}, ${!array[@]}, and ${#array[@]} are supported.
Associative arrays	Supported extension	declare -A map=([key]=value), element assignment/unset, key/value expansion, length expansion, local scope, and reusable declare -p output are supported.
Namerefs	Supported extension	declare -n/typeset -n/local -n can reference scalars or array elements. Reads, assignments, ${!ref}, normal unset, and unset -n follow Bash-style reference behavior.
Coprocesses	Supported extension	Simple commands, pipelines, unnamed compound commands, and the recommended coproc NAME { command; } form run asynchronously. Descriptors are published in NAME[0]/NAME[1], the PID in NAME_PID, dynamic descriptor redirection is supported, and read -u can consume the output.
Extended globs	Supported, opt-in	Run cjshopt extglob on to enable ?(), *(), +(), @(), and !() in pathname expansion, [[ … ]], case, and parameter patterns. It is off by default and forced off in POSIX mode.
Case continuation	Supported extension	;& executes the next clause body without testing its pattern. ;;& continues testing subsequent patterns. Both are rejected in POSIX mode.
Brace range strides	Supported extension	Numeric and character ranges accept {start..end..stride}. Direction is inferred, and numeric zero padding is preserved.
Pattern replacement	Supported extension	${parameter/pattern/replacement} uses the leftmost-longest wildcard match; // replaces all matches and /#//% anchor a single replacement. Escaped slashes, character classes, and extglobs are supported.

for and select require a literal variable name and an unquoted in keyword before an explicit list. Malformed headers such as for i n 1 2; do ...; done report a syntax error with status 2. Omitting the list (for i; do ...; done) uses positional parameters; an explicit empty for list runs no iterations. Loop lists use normal word expansion, including quoted literals and brace ranges with surrounding or following words.

One-line function bodies are recognized by interactive validation, including CJSH's compact function sayhello {echo hello} form. For conventional shell syntax, use function sayhello { echo hello; }; for POSIX scripts, use sayhello() { echo hello; }.

Function headers may put the opening brace on the next line. Function bodies and command groups support mixed inline and multiline layouts, with quoted and escaped delimiters preserved as literal text. Syntax-only mode (-n) rejects unfinished function bodies and control-flow blocks.

Interactive validation treats then, do, fi, done, and esac as control keywords only where a command can begin. Using those words as arguments, in quotes, or in comments does not complete an unfinished block.

Configuration

CJSH intentionally uses its own option interface rather than implementing Bash's shopt builtin:

cjshopt extglob on
cjshopt extglob off
cjshopt extglob status

Add the desired command to ~/.cjshrc to apply it to future interactive sessions.

Known boundaries

• --posix is a compatibility mode, not a standards certification.
• Only one coprocess connection is retained by the parent shell at a time. Starting another coprocess closes the parent's previous coprocess descriptors.
• Associative-array enumeration is deterministic and key-sorted in CJSH. Scripts should not depend on Bash or Zsh producing the same enumeration order.
• Bash-specific shopt names and the wider Bash option matrix are not aliases for cjshopt.
• Zsh-only parameter modifiers, glob qualifiers, option dialect, modules, and completion language are outside the Bash-style compatibility surface listed above.

For maximally portable scripts, continue to target POSIX sh syntax and test with cjsh --posix.