bash [-d: 未找到命令
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[-d: command not found
提问by user886596
As per this answer: Unix Bash Shell Programming if directory exists, I'm trying to check if a directory exists. However, when I run this, I get line 1: [-d: command not found. What am I doing wrong here?
根据这个答案：Unix Bash Shell Programming if directory exists，我正在尝试检查目录是否存在。但是，当我运行它时，我得到line 1: [-d: command not found. 我在这里做错了什么？
if [-d "~/.ssl"]; then
echo '~/.ssl directory already exists'
else
sudo mkdir ~/.ssl/
fi
回答by kojiro
[-d
is not a command.
不是命令。
[ -d
is the testcommand with the -d option.
是test带有 -d 选项的命令。
Space matters.
空间很重要。
(Also, the [command needs to end with a ]parameter, which likewise has to be separated from other arguments by whitespace.)
（此外，该[命令需要以]参数结尾，同样必须用空格将其与其他参数分开。）
That's the crux of the matter. There are a couple of other issues, though:
这就是问题的关键。但是，还有一些其他问题：
- If you quote the tilde, it doesn't expand. (This is one of the rare place where you may want to avoid quotes.) Quotes are great, though, so why not write
"$HOME/.ssl"? (There's a subtle difference between ~ and "$HOME", but it doesn't matter for most uses.) - You probably have your checks reversed – right now you're trying to create the directory only if it already exists.
- 如果你引用波浪号，它不会扩展。（这是您可能希望避免引用的罕见地方之一。）不过，引用很棒，那么为什么不写
"$HOME/.ssl"呢？（ ~ 和 "$HOME" 之间有细微的区别，但对于大多数用途来说并不重要。） - 您可能已经取消了检查 – 现在您仅在目录已经存在的情况下才尝试创建该目录。
Honestly, all you really need is probably:
老实说，您真正需要的可能是：
if mkdir -p ~/.ssl; then
# Do stuff with new directory
else
# Handle failure (but keep in mind `mkdir` will have its own error output)
fi
