linux - bash 中的简单 while 循环

Question

我已经开始学习 bash 脚本。我写了简单的 while 循环，但它不起作用。 它说:找不到命令。有人知道为什么吗？ 这是我的代码:

let x=5; while [$x -lt 10];do echo "x is : $x";let x=$x+1; done

Answer 1

添加空格。

while [ $x -lt 10 ];

有关更多信息，请参阅对 How to use double or single bracket, parentheses, curly braces 的回答:

A single bracket ([) usually actually calls a program named [; man test or man [ for more info. Example:

$ VARIABLE=abcdef
$ if [ $VARIABLE == abcdef ] ; then echo yes ; else echo no ; fi
yes

此外，这就是 info test 对此事的看法:

'test' has an alternate form that uses opening and closing square brackets instead a leading 'test'. For example, instead of 'test -d /', you can write '[ -d / ]'. The square brackets must be separate arguments; for example, '[-d /]' does not have the desired effect. Since 'test EXPR' and '[ EXPR ]' have the same meaning, only the former form is discussed below.

因此，等效项如下所示:

let x=5; while test $x -lt 10;do echo "x is : $x";let x=$x+1; done