bash shell本身包含了内置命令。
如何在Linux/Apple OS X/* BSD/Unix等操作系统上列出所有内置的bash命令，而不阅读大型bash手册页？
内置的Shell只是从shell本身直接执行的命令或者从shell调用的函数。

bash shell直接执行命令，而无需调用其他程序。
您可以使用" help"命令查看Bash内置信息。
有不同类型的内置命令。

内置命令类型

• Bourne Shell Builtins：从Bourne Shell继承的构建命令。
• Bash内置文件：特定于Bash的内置文件表。
• 修改Shell行为：内置程序可以修改Shell属性和可选行为。
• 特殊内置函数：POSIX专门分类的内置命令。

如何查看所有bash内置函数

执行以下命令：

$ help
$ help | less
$ help | grep read

输出示例：

GNU bash, version 4.1.5(1)-release (x86_64-pc-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 hist>
(( expression ))                        if COMMANDS; then COMMANDS; [ elif C>
. filename [arguments]                  jobs [-lnprs] [jobspec ...] or jobs >
:                                       kill [-s sigspec | -n signum | -sigs>
[ arg... ]                              let arg [arg ...]
[[ expression ]]                        local [option] name[=value] ...
alias [-p] [name[=value] ... ]          logout [n]
bg [job_spec ...]                       mapfile [-n count] [-O origin] [-s c>
bind [-lpvsPVS] [-m keymap] [-f filen>  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]...)>  read [-ers] [-a array] [-d delim] [->
cd [-L|-P] [dir]                        readarray [-n count] [-O origin] [-s>
command [-pVv] command [arg ...]        readonly [-af] [name[=value] ...] or>
compgen [-abcdefgjksuv] [-o option]  >  return [n]
complete [-abcdefgjksuv] [-pr] [-DE] >  select NAME [in WORDS ... ;] do COMM>
compopt [-o|+o option] [-DE] [name ..>  set [--abefhkmnptuvxBCHP] [-o option>
continue [n]                            shift [n]
coproc [NAME] command [redirections]    shopt [-pqsu] [-o] [optname ...]
declare [-aAfFilrtux] [-p] [name[=val>  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] [na>  times
eval [arg ...]                          trap [-lp] [[arg] signal_spec ...]
exec [-cl] [-a name] [command [argume>  true
exit [n]                                type [-afptP] name [name ...]
export [-fn] [name[=value] ...] or ex>  typeset [-aAfFilrtux] [-p] name[=val>
false                                   ulimit [-SHacdefilmnpqrstuvx] [limit>
fc [-e ename] [-lnr] [first] [last] o>  umask [-p] [-S] [mode]
fg [job_spec]                           unalias [-a] name [name ...]
for NAME [in WORDS ... ] ; do COMMAND>  unset [-f] [-v] [name ...]
for (( exp1; exp2; exp3 )); do COMMAN>  until COMMANDS; do COMMANDS; done
function name { COMMANDS ; } or name >  variables - Names and meanings of so>
getopts optstring name [arg]            wait [id]
hash [-lr] [-p pathname] [-dt] [name >  while COMMANDS; do COMMANDS; done
help [-dms] [pattern ...]               { COMMANDS ; }

另一种选择是使用NA命令：

compgen -b
compgen -b | more

查看内置Bash的信息

要获取详细信息，请运行：

help command
help read

要仅获得带有简短描述的所有内置列表，请执行：

$ help -d

查找内置语法和其他选项

使用以下语法查找有关内置命令的更多信息：

help name
help cd
help fg
help for
help read
help :

输出示例：

:: :
    Null command.
 
    No effect; the command does nothing.
 
    Exit Status:
    Always succeeds

找出命令是内部命令(内置命令)还是外部命令

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

输出示例：

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