Skip to content

Language Compatibility Inventory

CJSH is a POSIX-focused shell with native extensions. It does not claim formal POSIX certification or Bash/Zsh emulation. 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 shopt -s extglob to enable ?(), *(), +(), @(), and !() in pathname expansion, [[ … ]], case, and parameter patterns. It is off by default and forced off in POSIX mode.
Case continuation POSIX.1-2024 and extension ;& executes the next clause body without testing its pattern and is available in POSIX mode. ;;& continues testing subsequent patterns and is 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

Language options use shopt; editor configuration and dialect selection use cjshopt:

shopt -s extglob
shopt -u extglob
shopt -p extglob
cjshopt dialect posix
cjshopt dialect status
cjshopt dialect cjsh

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

Known boundaries

  • --posix targets POSIX.1-2024, with explicit extension restrictions and dedicated mode tests. It is 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.
  • cjsh supports its native dialect and strict POSIX mode. It does not provide a Bash compatibility mode. The shopt registry is deliberately limited; unknown options fail.
  • Zsh-only parameter modifiers, glob qualifiers, option dialect, modules, and completion language are outside the supported extensions listed above.

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