在字符串外带有 $ 字符的 Bash 回显
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Bash echo with an $ character outside the string
提问by u351545
Can anyone explain what is the difference between
谁能解释一下有什么区别
echo $"Starting $CMD"
and
和
echo "String $CMD"
They seem to look the same.
他们似乎看起来一样。
回答by larsks
Look up the QUOTINGsection of the bashman page:
查看手册页的QUOTING部分bash：
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 an escape character
- \f form feed
- \n new line
- \r carriage return
- \t horizontal tab
- \v vertical tab
- \ backslash
- \' single 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)
- \cx a control-x character
The expanded result is single-quoted, as if the dollar sign had not been present.
表格
$'string'中的词被特殊处理。单词扩展为字符串，并按照 ANSI C 标准的规定替换反斜杠转义字符。反斜杠转义序列（如果存在）按如下方式解码：
- \a 警报（响铃）
- \b 退格
- \e 转义字符
- \f 换页
- \n 换行
- \r 回车
- \t 水平制表符
- \v 垂直制表符
- \ 反斜杠
- \' 单引号
- \nnn 八位字符，其值为八进制值 nnn（一到三位数）
- \xHH 八位字符，其值为十六进制值 HH（一个或两个十六进制数字）
- \cx 一个 control-x 字符
扩展结果是单引号的，就好像美元符号不存在一样。
And note the follow description double quoted strings preceded by $($"string"):
并注意以下以$( $"string")开头的双引号字符串说明：
A double-quoted string preceded by a dollar sign ($) will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted.
以美元符号 ($) 开头的双引号字符串将使字符串根据当前区域设置进行翻译。如果当前语言环境是 C 或 POSIX，则忽略美元符号。如果字符串被翻译和替换，则替换是双引号。
回答by kojiro
$""is a form of quoting that is used for language translation. If you invoke bash with the -Dflag it will print out all such strings. When the locale is Cor POSIX, this form of quotation doesn't do anything.
$""是一种用于语言翻译的引用形式。如果您使用-D标志调用 bash，它将打印出所有此类字符串。当语言环境是Cor 时POSIX，这种形式的引用不做任何事情。
These strings are used by gettextto look up appropriate translations. For example, if your script has the string $"Hello, World"and you have properly installed MO files for translating that string into, say, French, you could execute your script this way:
这些字符串用于gettext查找适当的翻译。例如，如果您的脚本具有字符串$"Hello, World"并且您已正确安装用于将该字符串翻译成法语的 MO 文件，您可以通过以下方式执行您的脚本：
LANGUAGE=fr_FR ./yourscript
and expect all instances of $"Hello, World"to be output as Bonjour, Tout le Monde(assuming that is what is actually in your translation file).
并期望 的所有实例都$"Hello, World"输出为Bonjour、Tout le Monde（假设这就是您的翻译文件中的实际内容）。
Translation is not magic or automatic, so you must provide the translation engine with whatever translation strings it doesn't already have.
翻译不是魔术或自动的，因此您必须向翻译引擎提供它尚未提供的任何翻译字符串。
(PS - the guide I linked to does mention this security bug, but you may miss it if you skim, so I highlight it again here.)
（PS - 我链接的指南确实提到了这个安全漏洞，但如果你略读，你可能会错过它，所以我在这里再次强调它。）
