对于bash shell本身包含的内置命令，我们如何在Linux / Apple OS X / *BSD / 类Unix操作系统上全部列出他们，并且无需查阅大量得bash手册？
shell 内置命令就是一个命令或一个函数，从 shell 中调用，它直接在 shell 中执行。bash shell 直接执行该命令而无需调用其他程序。你可以使用help命令查看bash内置命令的信息。这里有很多种类型的内置命令。
内置命令类型
1.Bourne Shell 内置命令：内置命令继承自 Bourne Shell。
2.Bash内置命令：特定于 Bash 的内置命令表
3.修改 Shell 行为：修改 shell 属性和可选行为的内置命令。
4.特别的内置命令：由 POSIX 特别分类的内置命令。
如何查看bash内置命令
有以下的命令：
$ help
$ help | less
$ help | grep read样例输出：
[root@develop ~]# help
GNU bash, version 4.1.2(2)-release (x86_64-redhat-linux-gnu)
These shell commands are defined internally. Type `help' to see this list.
Type `help name' to find out more about the function `name'.
Use `info bash' to find out more about the shell in general.
Use `man -k' or `info' to find out more about commands not in this list.
A star (*) next to a name means that the command is disabled.
job_spec [&] history [-c] [-d offset] [n] or history -anrw [filename] or history -ps arg [arg...]
(( expression )) if COMMANDS; then COMMANDS; [ elif COMMANDS; then COMMANDS; ]... [ else COMMANDS; ] fi
. filename [arguments] jobs [-lnprs] [jobspec ...] or jobs -x command [args]
: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
[ arg... ] let arg [arg ...]
[[ expression ]] local [option] name[=value] ...
alias [-p] [name[=value] ... ] logout [n]
bg [job_spec ...] mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
bind [-lpvsPVS] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-> popd [-n] [+N | -N]
break [n] printf [-v var] format [arguments]
builtin [shell-builtin [arg ...]] pushd [-n] [+N | -N | dir]
caller [expr] pwd [-LP]
case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac read [-ers] [-a array] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeou>
cd [-L|-P] [dir] readarray [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array>
command [-pVv] command [arg ...] readonly [-af] [name[=value] ...] or readonly -p
compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] > return [n]
complete [-abcdefgjksuv] [-pr] [-DE] [-o option] [-A action] [-G globpat] [-W wordlist] [-> select NAME [in WORDS ... ;] do COMMANDS; done
compopt [-o|+o option] [-DE] [name ...] set [--abefhkmnptuvxBCHP] [-o option-name] [arg ...]
continue [n] shift [n]
coproc [NAME] command [redirections] shopt [-pqsu] [-o] [optname ...]
declare [-aAfFilrtux] [-p] [name[=value] ...] source filename [arguments]
dirs [-clpv] [+N] [-N] suspend [-f]
disown [-h] [-ar] [jobspec ...] test [expr]
echo [-neE] [arg ...] time [-p] pipeline
enable [-a] [-dnps] [-f filename] [name ...] times
eval [arg ...] trap [-lp] [[arg] signal_spec ...]
exec [-cl] [-a name] [command [arguments ...]] [redirection ...] true
exit [n] type [-afptP] name [name ...]
export [-fn] [name[=value] ...] or export -p typeset [-aAfFilrtux] [-p] name[=value] ...
false ulimit [-SHacdefilmnpqrstuvx] [limit]
fc [-e ename] [-lnr] [first] [last] or fc -s [pat=rep] [command] umask [-p] [-S] [mode]
fg [job_spec] unalias [-a] name [name ...]
for NAME [in WORDS ... ] ; do COMMANDS; done unset [-f] [-v] [name ...]
for (( exp1; exp2; exp3 )); do COMMANDS; done until COMMANDS; do COMMANDS; done
function name { COMMANDS ; } or name () { COMMANDS ; } variables - Names and meanings of some shell variables
getopts optstring name [arg] wait [id]
hash [-lr] [-p pathname] [-dt] [name ...] while COMMANDS; do COMMANDS; done
help [-dms] [pattern ...] { COMMANDS ; }
[root@develop ~]#
另外一种选择是使用下列命令：
compgen -b
compgen -b | more查看 Bash 的内置命令信息
运行以下得到详细信息：
help command
help read只显示所有内置命令和简要描述，执行如下：
help -d查找内置命令的语法和其他选项
使用下列语法去找出更多的相关内置命令：
help name
help cd
help fg
help for
help read
help :样例输出：
:: :
Null command.
No effect; the command does nothing.
Exit Status:
Always succeeds找出一个命名时内部（内置）的还是外部的
使用type命令或者command命令：
type -a command-name-here
type -a cd
type -a uname
type -a :
type -a ls或者
type -a cd uname : ls uname样例输出：
cd is a shell builtin
uname is /bin/uname
: is a shell builtin
ls is aliased to `ls --color=auto'
ls is /bin/ls
l is a function
l ()
{
ls --color=auto
}或者
command -V ls
command -V cd
command -V foo[root@develop ~]# help bg
bg: bg [job_spec ...]
Move jobs to the background.
Place the jobs identified by each JOB_SPEC in the background, as if they
had been started with `&'. If JOB_SPEC is not present, the shell's notion
of the current job is used.
Exit Status:
Returns success unless job control is not enabled or an error occurs.
[root@develop ~]# type -a cd
cd is a shell builtin
[root@develop ~]# command -V ls
ls is aliased to `ls --color=auto'
[root@develop ~]#
翻译自：
Linux / Unix Bash Shell List All Builtin Commands
https://www.cyberciti.biz/faq/linux-unix-bash-shell-list-all-builtin-commands/