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    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

    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,谢谢大家对脚本之家的支持。

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