bash&shell系列文章：http://www.cnblogs.com/f-ck-need-u/p/7048359.html

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有些時候在某些服務管理腳本中看到$"$string"或$"string"，經過一些測試，又發現引號外面的$有和沒有是一樣的。一直也沒去找究竟，剛才有人問了我，于是就去翻了下man bash，找到了解釋。

(1).如果沒有特殊定制bash環境或有特殊需求，$"string"和"string"是完全等價的，使用$""只是為了保證本地化。

以下是man bash關于$""的解釋：

A double-quoted string preceded by a dollar sign ($"string") will cause the string to be translated according to the current locale. Ifthe current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted.

(2).還有$后接單引號的$'string'，這在bash中被特殊對待：會將某些反斜線序列(如\n，\t，\"，\'等)繼續轉義，而不認為它是字面符號(如果沒有$符號，單引號會強制將string翻譯為字面符號，包括反斜線)。簡單的例子：

[root@xuexi ~]# echo 'a\nb' a\nb [root@xuexi ~]# echo $'a\nb' a b

以下是man bash里關于$'的說明：

Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows:\a alert (bell)\b backspace\e\E an escape character\f form feed\n new line\r carriage return\t horizontal tab\v vertical tab\\ backslash\' single quote\" double quote\nnn the eight-bit character whose value is the octal value nnn (one to three digits)\xHH the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)\uHHHH the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)\UHHHHHHHHthe Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight hex digits)\cx a control-x character

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