Built-in commands compared

This page lists every built-in command of dash, bash, zsh and luish, and for those luish lacks, what to use instead. It complements luish, dash, bash and zsh; Built-in commands documents luish’s own built-ins in full.

The lists are those of dash 0.5.12 (Debian and Ubuntu’s), bash 5.2 (compgen -b), zsh 5.9 (${(k)builtins} with no startup files, which includes the built-ins of modules zsh loads on demand, such as zstyle and the completion system’s) and luish 0.7.0. zsh’s other modules, loaded with zmodload (such as zsh/files, zsh/datetime or zsh/system), add more, and bash can load more with enable -f; those are not listed.

	dash	bash	zsh	luish
Built-ins	38	61	103	54, and 8 more in interactive shells

In the tables, ✓ marks a built-in, – its absence, and i a built-in that luish has only in interactive shells (and their subshells), so that scripts find the same commands as under dash; there, __luish_internal NAME runs it.

POSIX special built-ins

All four shells have these. As POSIX requires, an error in a special built-in exits a non-interactive shell, and assignments before one stay set; luish follows dash in both.

Built-in	dash	bash	zsh	luish	luish compared with bash and zsh
:	✓	✓	✓	✓
.	✓	✓	✓	✓	Further arguments are the positional parameters while the file runs, as in bash and zsh
break	✓	✓	✓	✓
continue	✓	✓	✓	✓
eval	✓	✓	✓	✓
exec	✓	✓	✓	✓	No -a, -c or -l
exit	✓	✓	✓	✓
export	✓	✓	✓	✓	Takes arrays (export a=(x y) sets and exports a); no -n or -f (bash)
readonly	✓	✓	✓	✓	Takes arrays; no -f (bash)
return	✓	✓	✓	✓
set	✓	✓	✓	✓	POSIX’s options, with -o pipefail; luish’s own and zsh-named options go through setopt (or -o NAME)
shift	✓	✓	✓	✓
times	✓	✓	✓	✓
trap	✓	✓	✓	✓	Signals and EXIT; no ERR, DEBUG or RETURN (bash), ZERR or TRAP* functions (zsh), and no -p or -l
unset	✓	✓	✓	✓	-f and -v; elements of arrays (unset 'a[1]')

POSIX regular built-ins and utilities

The commands that POSIX requires to be built in (alias, bg, cd, command, fc, fg, getopts, hash, jobs, kill, read, type, ulimit, umask, unalias, wait), and the utilities that shells build in for speed.

Built-in	dash	bash	zsh	luish	luish compared with bash and zsh
[, test	✓	✓	✓	✓	POSIX’s operators, as dash; -v NAME only in [[ ... ]]
alias	✓	✓	✓	✓	zsh’s options (-g and -s for global and suffix aliases, -r, -m, -L, +); no -p (bash)
bg	✓	✓	✓	✓
cd	✓	✓	✓	✓	-L, -P, -e, cd -, CDPATH, and zsh’s auto_pushd; no cd OLD NEW (zsh)
command	✓	✓	✓	✓	-p, -v, -V
echo	✓	✓	✓	✓	As dash’s: escapes such as \t are always interpreted, and -n is the only option (bash needs -e; zsh interprets them unless BSD_ECHO is set)
false, true	✓	✓	✓	✓
fc	– [1]	✓	✓	✓	-e, -l, -n, -r, -s; no times (zsh’s -d, -i) or zsh’s other options
fg	✓	✓	✓	✓
getopts	✓	✓	✓	✓
hash	✓	✓	✓	✓	-r; no -d, -p, -t, -l. Rarely needed: luish clears the cache itself when a PATH directory changes
jobs	✓	✓	✓	✓	-l, -p, and -i, a menu to act on the jobs; no -r, -s, -n, -x
kill	✓	✓	✓	✓	-s, -SIGNAL, -l, and jobs (%1)
printf	✓	✓	✓	✓	%b; no -v or %q
pwd	✓	✓	✓	✓	-L, -P
read	✓	✓	✓	✓	-r, -p, and arrays with -a (bash) or -A (zsh); no -t, -n, -s, -d, -u, -e or zsh’s -k, -q
type	✓	✓	✓	✓	No options (bash’s -a, -t, -p; zsh’s -a, -w …); names the plugin of a built-in that a plugin added
ulimit	✓	✓	✓	✓	-H, -S, -a and dash’s resource letters
umask	✓	✓	✓	✓	-S
unalias	✓	✓	✓	✓	-a, and zsh’s -m, -s
wait	✓	✓	✓	✓	Jobs and process ids; no -n, -f or -p (bash)

Common extensions

Built-ins outside POSIX that luish has, mostly as zsh has them.

Built-in	dash	bash	zsh	luish	Notes
bindkey	–	–	✓	i	zsh’s, for the emacs keymap and the widgets luish has; keys can also be named (Up, Ctrl-Right). No other keymaps (-M) and no user-defined widgets
builtin	–	✓	✓	✓
caller	–	✓	–	✓	bash’s
chdir	✓	–	✓	✓	The same as cd
declare, typeset	–	✓	✓	✓	-a, -A, -f, -g, -i, -l, -p, -r, -u, -U, -x, and +f; no namerefs (bash’s -n), floating point (zsh’s -E, -F), padding (zsh’s -L, -R, -Z), -t or tied variables (zsh’s -T)
disown	–	✓	✓	✓	As in zsh, with bash’s -a, -r and -h, and process ids
dirs, pushd, popd	–	✓	✓	✓	As in zsh: -q, -L, -P, +n, -n; dirs -l, -p, -v, -c
help	–	✓	–	i	Help for luish’s built-ins, from the pages in Built-in commands
let	–	✓	✓	✓	As in zsh; integers only
local	✓	✓	✓	✓	Special, as in dash. Takes typeset’s options and arrays (local a=(x y)). Without a value, keeps the outer value, as in dash (in bash and zsh it starts unset or empty)
print	–	–	✓	i	zsh’s, with its options except -p (no coprocesses) and -S
setopt, unsetopt	–	–	✓	✓	zsh’s names for the options luish has, and luish’s grouped names (history.share) and NAME=VALUE settings
shopt	–	✓	–	✓	bash’s, setting luish’s options that do the same (glob.star for globstar); the options luish lacks can’t be set
source	–	✓	✓	✓	As in zsh: a name without / is looked for in the current directory first
vared	–	–	✓	i	zsh’s, without its widget options (-i, -f) and -t

Built-ins that luish lacks

In both bash and zsh

Built-in	What it does	In luish
enable (zsh’s also disable)	Turn built-ins off or on	command NAME or a full path runs the program instead
history	List the history	fc -l
logout	Exit a login shell	exit
suspend	Stop the shell	kill -STOP $$

bash only

Built-in	What it does	In luish
bind	readline key bindings	bindkey, or [bindkey] in config.toml
compgen, complete, compopt	Programmable completion	Completers in Rhai, from plugins; std.bash-completion runs bash’s completion scripts
mapfile, readarray	Read lines into an array	A loop: while IFS= read -r l; do a+=("$l"); done

zsh only

Built-in	What it does	In luish
-	Run a command as a login shell would (argv[0] with -)	None
autoload	Define a function to be loaded from fpath on first use	None: . the file in a startup file, which the startup cache makes cheap
bye	Exit	exit
compadd, comparguments, compcall, compdescribe, compfiles, compgroups, compquote, compset, comptags, comptry, compvalues	The completion system (compsys)	Completers in Rhai, from plugins
compctl	The old completion system	As above
echotc, echoti	Terminal capabilities	tput
emulate	Emulate sh, ksh or csh	None: luish is always an sh
float, integer	Floating-point and integer variables	typeset -i for integers; no floating point
functions	List or define functions	typeset -f
getln, pushln	The buffer stack	None
limit, unlimit	csh-style resource limits	ulimit
log	Report logins and logouts (watch)	None
noglob	Run a command without globbing	set -f, or quoting
private	Variables not seen by called functions	local (seen by called functions)
r	Re-run a command	fc -s (alias r='fc -s')
rehash	Clear the command cache	Rarely needed (automatic); hash -r
sched	Run commands at a given time	None
ttyctl	Freeze the terminal’s settings	None
unfunction, unhash	Remove functions, aliases or cached commands	unset -f, unalias, hash -r
whence, where, which	Describe or find commands	type, command -v, command -V. luish’s own where shows where variables were set
zcompile	Compile scripts	None needed for startup files: the startup cache saves their effect
zformat, zparseopts, zregexparse	Formatting and parsing helpers	printf, getopts, [[ =~ ]]
zle	Line editor widgets	bindkey binds keys to luish’s widgets; no user-defined widgets
zmodload	Load modules	Plugins, with extensions in Rhai that can add commands
zstyle	Style settings, mostly for completion	Settings in config.toml and setopt NAME=VALUE

luish’s own

Built-in	What it does
__luish_internal	Subcommands that are not needed often: check-cache (check the startup cache), savestate (print commands that restore the shell’s state), complete (show what Tab would offer), print-git-rev, and the interactive-only built-ins, which work there in scripts too
clipcopy (i)	Put text on the clipboard, through the terminal
plugin (i)	Load, list, add, fetch and update plugins
style (i)	Set or show the styles and colour schemes of the line editor
where (i)	Show where variables were set, with setopt vars.trace (also in scripts, while variables are traced)

Plugins can add further built-ins, written in Rhai (see Extensions).

Reserved words

Some commands that look like built-ins are reserved words, parsed with the command.

Word	dash	bash	zsh	luish	Notes
!, { }, case, for, if, until, while …	✓	✓	✓	✓	POSIX
[[ ]]	–	✓	✓	✓
function	–	✓	✓	✓
time	–	✓	✓	–	Runs the time program instead, which can’t time pipelines or shell functions
select	–	✓	✓	–
coproc	–	✓	✓	–
repeat, foreach, nocorrect	–	–	✓	–
declare, export, local, readonly, typeset, float, integer	–	–	✓	–	In zsh, these are reserved words so that local a=(x y) parses. luish parses such array assignments for its own built-ins, which remain built-ins

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[1]

Debian’s dash is built without a line editor, so it has no fc. Upstream dash built with libedit has one.