列出所有Bash Shell内置命令的方法示例

前言

shell有很多内置在其源代码中的命令。这些命令是内置的，所以shell不必到磁盘上搜索它们，执行速度因此加快。不同的shell内置命令有所不同。

内置命令包含在 bash shell 本身里面。我该如何在 linux / apple os x / *bsd / unix 类操作系统列出所有的内置 bash 命令，而不用去读大篇的 bash 操作说明页？

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。以下是几种不同类型的内置命令。

内置命令的类型

• bourne shell 内置命令：内置命令继承自 bourne shell。
• bash 内置命令：特定于 bash 的内置命令表。
• 修改 shell 行为：修改 shell 属性和可选行为的内置命令。
• 特别的内置命令：由 posix 特别分类的内置命令。

如何查看所有 bash 内置命令

有以下的命令：

$ help
$ help | less
$ help | grep read 

样例输出：

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

要仅得到所有带简短描述的内置命令的列表，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

找出一个命令是内部的（内置）还是外部的

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

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

view list bash built-ins command info on linux or unix

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。