为什么要周围有空格＆＃x27; [＆＃x27;和＆＃x27;]＆＃x27;在狂欢中？
我试图编写一个使用语句的bash脚本。
if[$CHOICE -eq 1];
该脚本给我错误，直到我在之前和之后给出一个空间[和
if [ $CHOICE -eq 1 ];
]在狂欢中很重要？
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
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一旦您掌握了
[是 命令 ，一个批次就变得更加清晰了！[是拼写“test”的另一种方法。但是，尽管它们完全相同
test事实证明有一个更详细的帮助页面。检查...以获取更多信息。
此外，请注意，我故意使用
帮助测试而不是MAN TEST。那是因为test和[是如今的壳命令。他们的功能集可能不同于/bin/test和/bin/[的coreutils，这是man页面中所述的命令。Once you grasp that
[is a command, a whole lot becomes clearer![is another way to spell "test".However while they do exactly the same,
testturns out to have a more detailed help page. Check...for more information.
Furthermore note that I'm using, by intention,
help testand notman test. That's becausetestand[are shell builtin commands nowadays. Their feature set might differ from/bin/testand/bin/[from coreutils which are the commands described in themanpages.来自另一个问题：
From another question:
[是命令，$ opeach应该是一个参数，但是通过执行[$ opeach>（之间没有任何空间[和$选择）您正在尝试运行一个名为的命令[$选择。命令的语法是：[is a command and$CHOICEshould be an argument, but by doing[$CHOICE(without any space between[and$CHOICE) you are trying to run a command named[$CHOICE. The syntax for command is:[是test命令。因此需要空间。[is atestcommand. So it requires space.值得注意的是，[也用于地球匹配，这可能会使您陷入困境。
It's worth noting that [ is also used in glob matching, which can get you into trouble.