Builtins — the reference

Every name built into the shell, grouped the way help groups them, with the same synopses help NAME prints — because this page IS help output: regenerate it with make docs-builtins (tools/gen_builtins_md.py), never edit it by hand. The help table itself is test-enforced against the dispatch table, so neither this page nor help can drift from what actually runs. 72 builtins; anything else on $PATH works as usual — type NAME says which is which.

navigation

cd — cd [-L|-P] [dir] | cd - | cd old new
change directory (honours CDPATH, - goes back)

dirs — dirs [-c]
display the directory stack

popd — popd [+N | -N] [-n]
pop the directory stack and cd there

pushd — pushd [dir | +N | -N] [-n]
push a directory on the stack and cd there

pwd — pwd [-L|-P]
print the working directory

output

echo — echo [-neE] [arg ...]
write arguments (-n no newline, -e escapes)

mapfile — mapfile [-d delim] [-n n] [-O idx] [-s n] [-t] [-u fd] [array]
read lines of input into an array

printf — printf [-v var] format [arg ...]
format and print, like printf(3)

read — read [-r] [-a arr] [-d delim] [-n n] [-N n] [-p str] [-t s] [name ...]
read one line into variables

readarray — readarray [-d delim] [-n n] [-O idx] [-s n] [-t] [-u fd] [array]
same as mapfile

umask — umask [-S] [-p] [mode]
show or set the file-creation mask

variables

declare — declare [-aAfFgiIlnrtux] [-p] [name[=value] ...]
declare variables and give them attributes

export — export [-p] [-n] [name[=value] ...]
put variables into the environment of commands

getopts — getopts optstring name [arg ...]
parse option arguments in a loop

let — let arg [arg ...]
evaluate arithmetic; status 1 if the last is 0

local — local [name[=value] ...]
declare variables local to a function

readonly — readonly [-p] [name[=value] ...]
make variables unassignable and unremovable

typeset — typeset [-aAfFgiIlnrtux] [-p] [name[=value]...]
same as declare

unset — unset [-f|-v] [name ...]
remove variables or functions

jobs

bg — bg [jobspec ...]
resume a stopped job in the background

fg — fg [jobspec]
bring a job to the foreground

jobs — jobs [-l] [-p] [jobspec ...]
list background jobs

kill — kill [-s sig|-n num|-sig] pid|job ... | kill -l
send a signal to a process or job

wait — wait [-n] [id ...]
wait for background jobs to finish

control

break — break [n]
leave a for/while/until loop

continue — continue [n]
start the next turn of a loop

return — return [n]
return from a function or a sourced file

shift — shift [n]
drop the first n positional parameters

commands

alias — alias [-p] [name[=value] ...]
define or list command aliases

builtin — builtin [name [args ...]]
run a shell builtin, bypassing function lookup

command — command [-pVv] name [arg ...]
run a command, ignoring functions and aliases

hash — hash [-lr] [-p path] [-dt] [name ...]
show or change the remembered command paths

type — type [-afptP] name [name ...]
say how a name would be resolved

unalias — unalias [-a] name [name ...]
remove aliases

tests

: — :
do nothing; the classic no-op

[ — [ expr ]
same as test; the closing ] is required

[[ — [[ expr ]]
conditional with pattern and regex matching

false — false
do nothing, unsuccessfully

test — test expr | [ expr ]
evaluate a conditional expression

true — true
do nothing, successfully

history

fc — fc [-e ed] [-lnr] [first] [last] | fc -s [pat=rep]
re-edit and re-run past commands

history — history [-c] [-d n] [n] | history -anrw [file]
show or edit the command history

shell

. — . filename [arguments]
read and run a file in the current shell

compgen — compgen [-abcdfkv] [-A action] [-W wordlist] [word]
print the completions the shell would offer for word

complete — complete [-abcdfkv] [-A action] [-W list] [-F fn] [-pr] name ...
register what to offer when completing an argument of name

compopt — compopt [-o|+o option] [-DEI] [name ...]
change a completion spec's options, or the running one's

eval — eval [arg ...]
join the arguments and run them as a command

exec — exec [command [arg ...]] [redirection ...]
replace the shell, or apply redirections to it

exit — exit [n]
leave the shell with status n

help — help [-s] [topic ...]
this. help NAME explains one topic

pretty — pretty [-p] | list | on NAME... | off NAME... | mode NAME
named presets for the shell's behaviour knobs

set — set [-abefhkmnptuvxCH] [-o opt] [--] [arg ...]
set shell options and positional parameters

shopt — shopt [-pqsu] [-o] [optname ...]
toggle the extra (non-POSIX) shell options

source — source filename [arguments]
same as .

times — times
print user and system time for the shell

trap — trap [-lp] [[action] signal ...]
run an action on a signal or on EXIT

ulimit — ulimit [-SHabcdefiklmnpqrstuvxPT] [limit]
show or set process resource limits

update — update [--now|--check|--version]
check for a newer hellish and install it

syntax

Not builtins — the grammar help also explains, kept here for the same one-stop reason.

for — for NAME [in WORD ...]; do LIST; done
loop over words

select — select NAME [in WORD ...]; do LIST; done
menu loop: number the words on stderr, read a choice into NAME

for(( — for ((exp1; exp2; exp3)); do LIST; done
C-style counting loop

while — while LIST; do LIST; done
loop while a list succeeds

until — until LIST; do LIST; done
loop until a list succeeds

if — if LIST; then LIST; [elif ...] [else LIST] fi
branch on a command's exit status

case — case WORD in PATTERN) LIST ;; ... esac
branch on a pattern match

function — name () { LIST; } | function name { LIST; }
define a function

(( — (( expression ))
arithmetic; status 0 when the value is non-zero

$(( — $(( expression ))
substitute the value of an arithmetic expression

$( — $( LIST ) orLIST``
substitute a command's output

redirection — > < >> 2>&1 <<EOF <<<word /dev/tcp/host/port
send a command's input and output elsewhere

pipeline — cmd1 | cmd2 [!] cmd1 |& cmd2
feed one command's output into the next

zsh

Only reachable when the dialect is armed (set -o zsh, emulate zsh, or sourcing a .zsh file) — see the zsh dialect.

add-zsh-hook — add-zsh-hook hook function
run a function on an event; only chpwd fires here

autoload — autoload [-Uz] name ...
define a function from a file on $fpath

bindkey — bindkey [-M keymap] seq widget
record a key binding for a zle widget

colors — colors
define $fg[..] $bg[..] $fg_bold[..] $reset_color like zsh's colors

compdef — compdef [args ...]
not supported: hellish has no zsh completion system

emulate — emulate [-L] {zsh|sh|ksh|bash}
switch dialect; in a function it reverts on return

is-at-least — is-at-least need [have]
0 when version have (default $ZSH_VERSION) is need or newer

print — print [-nrlP] [--] [arg ...]
zsh's echo: escapes on by default, -r turns them off

setopt — setopt [name ...]
turn on zsh-named shell options

unsetopt — unsetopt [name ...]
turn off zsh-named shell options

vcs_info — vcs_info
fill $vcs_info_msg_0_ with the git branch, zstyle formats honoured

zle — zle -N widget [fn] | zle widget
register a line-editor widget; key dispatch is not wired yet

zmodload — zmodload [args ...]
not supported: hellish has no loadable modules

zstyle — zstyle [pattern style value ...]
vcs_info formats/actionformats are honoured; the rest is stubbed