为什么波浪号 (~) 不在双引号内展开？

Question

我想检查隐藏的.git文件夹是否存在。首先想到的是使用：

if [ -d "~/.git" ]; then
   echo "Do stuff"
fi

但是 -d 显然不会查找隐藏文件夹。

Answer 1

问题与波浪号在双引号内有关。

要展开它，您需要将波浪号放在引号外：

if [ -d ~/".git" ]; then   # note tilde outside double quotes!
   echo "Do stuff"
fi

或者，或者，正如 hek2mgl 在下面评论的那样，使用 $HOME 而不是 ~：

if [ -d "$HOME/.git" ]

来自 Tilde expansion 中的 POSIX：

A "tilde-prefix" consists of an unquoted character at the beginning of a word, followed by all of the characters preceding the first unquoted in the word, or all the characters in the word if there is no .

来自 POSIX Double Quotes:

Enclosing characters in double-quotes ( "" ) shall preserve the literal value of all characters within the double-quotes, with the exception of the characters dollar sign, backquote, and backslash, as follows:

您可以在 Why doesn't the tilde (~) expand inside double quotes? from the Unix & Linux Stack 中找到进一步的解释。