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內置命令包含在 bash shell 本身里面。我該如何在 Linux / Apple OS X / *BSD / Unix 類操作系統列出所有的內置 bash 命令，而不用去讀大篇的 bash 操作說明頁？

shell 內置命令就是一個命令或一個函數，從 shell 中調用，它直接在 shell 中執行。 bash shell 直接執行該命令而無需調用其他程序。你可以使用 help 命令查看 Bash 內置命令的信息。以下是幾種不同類型的內置命令。

內置命令的類型

1. Bourne Shell 內置命令：內置命令繼承自 Bourne Shell。
2. Bash 內置命令：特定于 Bash 的內置命令表。
3. 修改 Shell 行為：修改 shell 屬性和可選行為的內置命令。
4. 特別的內置命令：由 POSIX 特別分類的內置命令。

如何查看所有 bash 內置命令

有以下的命令：

$ help
$ help | less
$ help | grep read 

樣例輸出：

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 ; }

另外一種選擇是使用下列命令：

compgen -b
compgen -b | more

查看 Bash 的內置命令信息

運行以下得到詳細信息：

help command
help read

要僅得到所有帶簡短描述的內置命令的列表，執行如下:

$ help -d

查找內置命令的語法和其他選項

使用下列語法去找出更多的相關內置命令：

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

樣例輸出：

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

找出一個命令是內部的（內置）還是外部的

使用 type 命令或 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

樣例輸出：

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

View list bash built-ins command info on Linux or Unix