出自bash的faq，仔細看看。順便翻譯學習一下。

代碼如下:
Section C: Differences from other Unix shells
C：跟其他UNIX shells腳本的區別
C1) How does bash differ from sh, the Bourne shell?
C1） bash和 sh、Bourne shell的區別
This is a non-comprehensive list of features that differentiate bash
from the SVR4.2 shell.  The bash manual page explains these more
completely.
這時一個不全面的bash和SVR4.2 shell特性區別的列表，bash手冊解釋的更詳細
Things bash has that sh does not:
bash特有的功能：
        long invocation options
        長選項的調用
        [+-]O invocation option
        -l invocation option
        `!' reserved word to invert pipeline return value
         ！嘆號保留字對管道返回的值取反
        `time' reserved word to time pipelines and shell builtins
         time保留字測試管道或內建命令耗時情況
        the `function' reserved word
        the `select' compound command and reserved word
        select復合命令和保留字
        arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
        算術命令：for ((expr1 ; expr2; expr3 )); do list; done
        new $'...' and $"..." quoting
        新的引用方法$'...'  $"..."
        the $(...) form of command substitution
        $(...) 命令替代用法
        the $(<filename) form of command substitution, equivalent to
                $(cat filename)
        $(<filename)形式的命令的替換，相當于$(cat filename)
        the ${#param} parameter value length operator
        ${#param} 測試參數param的值的長度
        the ${!param} indirect parameter expansion operator
        ${!param} 間接參數擴展操作
        the ${!param*} prefix expansion operator
        ${!param*} 前綴擴展操作
        the ${param:offset[]} parameter substring operator
       ${param:ffset[]}參數通過偏移量截取子串操作