Bash while 在两次之间循环

Bash while loop between two times

提问by Iz3k34l

I am trying to write a bash script that will loop if the time is after certain time and before a certain time. Here is what i have got but it gives me an error;

我正在尝试编写一个 bash 脚本，如果时间在特定时间之后和特定时间之前将循环。这是我所得到的，但它给了我一个错误；

#!/bin/bash

while [ date +"%T" -gt '06:00:00' && date +"%T" -lt '21:00:00'];
  do
  ##echo `php mainstatquery.php`
  echo "Hello World";
  sleep 5;
done

and this is the error

这是错误

./timer.sh: line 3: [: missing `]'

If anyone could point me in the right direction.

如果有人能指出我正确的方向。

采纳答案by David W.

Here's an easy way to understand your whileproblems:

以下是了解您的while问题的简单方法：

The [is an actual Unix command. Do ls /bin/[and you'll see. It's a link to the /bin/testcommand. Do a man testfrom the command line and see the various teststhat can be done.

这[是一个实际的 Unix 命令。做ls /bin/[，你会看到。这是/bin/test命令的链接。man test从命令行执行 a并查看可以执行的各种测试。

What the whiledoes is execute the command you give it, and if it returns a zero exit status, the whilestatement is considered true and the statement will continue. You can do things like this:

它的while作用是执行您给它的命令，如果它返回零退出状态，则该while语句被认为是正确的，并且该语句将继续。你可以做这样的事情：

while sleep 2
do
   echo "I slept for two seconds"
done

All the testcommand does is do some sort of testing (file tests, tests of equality, etc.) and return a zero if the statement is true and a non-zero otherwise:

所有的test命令确实是做一些测试（文件测试，平等的测试等），并返回一个零，如果该声明是真实的和非否则为零：

$  test 2 -gt 3
$ echo $?
1   <- That statement is false

$ [ 2 -lt 3 ]   #The test command using square brackets
$ echo $?
0  <- That statement is true.

Take a look at the manpage for testand you'll see all valid tests. This:

查看手册页test，您将看到所有有效的测试。这个：

while [ date +"%T" -gt '06:00:00' && date +"%T" -lt '21:00:00']

is the same as

是相同的

while test date +"%T" -gt '06:00:00' && date +"%T" -lt '21:00:00'

Let's go through a few things here:

让我们来看看这里的一些事情：

• date + %T is not a valid operator for the testcommand.

• date + %T 不是test命令的有效运算符。

The testcommand can't execute a command internally. What you need to do is to put that command in $(..)and probably use quotes to play it safe. Thus:

该test命令无法在内部执行命令。您需要做的是将该命令放入$(..)并可能使用引号来确保安全。因此：

while test "$(date +"%T")" -gt '06:00:00' && "$(date +"%T")" -lt '21:00:00'

• The &&is not a valid operator in the testcommand. What you probably want is -awhich is the andconjunctive for stringing together two tests in test.

• 该&&不是在一个有效的操作test命令。你可能想要的是-a这是和连接性在两个测试串在一起test。

This would give you:

这会给你：

while test $(date +"%T") -gt '06:00:00' -a "$(date +"%T")" -lt '21:00:00'

• There are two separate greater thantest operators for comparisons. One is for strings and one is for integers. The -gtis the test for integers. Since you're dealing with strings, you need to use >:

  while test "$(date +"%T")" > '06:00:00' -a "$(date +"%T")" < '21:00:00'

• 有两个单独的大于测试运算符用于比较。一种用于字符串，一种用于整数。这-gt是对整数的测试。由于您正在处理字符串，因此您需要使用>：

  而测试 "$(date +"%T")" > '06:00:00' -a "$(date +"%T")" < '21:00:00'

As an alternative, you could have also used the &&conjunctive instead of -a, but each side of the &&would have to be separate test statements:

作为替代方案，您也可以使用&&连接词代替-a，但 的每一侧&&都必须是单独的测试语句：

while test "$(date +"%T")" > '06:00:00' && test "$(date +"%T")" < '21:00:00'

Now, let's convert the testsyntax back to [...]because it's easier on the eyes

现在，让我们将test语法转换回，[...]因为它看起来更容易

while [ "$(date +"%T")" > '06:00:00' -a "$(date +"%T")" < '21:00:00' ]

OR

或者

while [ "$(date +"%T")" > '06:00:00' ] && [ "$(date +"%T")" < '21:00:00' ]

By the way, the internal [[...]]is better -- especially with the >sign since it can be interpreted by the shell as a file redirect.

顺便说一句，内部[[...]]更好——尤其是带有>符号的，因为它可以被外壳程序解释为文件重定向。

while [[ "$(date +"%T")" > '06:00:00' -a "$(date +"%T")" < '21:00:00' ]]

OR

或者

while [[ "$(date +"%T")" > '06:00:00' ]] && [[ "$(date +"%T")" < '21:00:00' ]]

回答by fedorqui 'SO stop harming'

You cannot compare an entire hour like that.

你不能像那样比较一整个小时。

As you are just checking the hour (6<=x<=21), use date "+%H"to do that:

由于您只是在检查小时 (6<=x<=21)，因此请使用以下date "+%H"方法：

while [ $(date +"%H") -gt 06 ] && [ $(date +"%H") -lt 21 ];
  do
  ##echo `php mainstatquery.php`
  echo "Hello World";
  sleep 5;
done

Also take into consideration that the dateexpression has to be called with $()to make it get the result. And your

还要考虑date到必须调用表达式才能$()获得结果。和你的

while [  date +"%T" -gt '06:00:00'   &&      date +"%T" -lt '21:00:00'];
       $(        )                ]  &&  [  $(        )              ^ need space

Finally, the logical condition is not well written. The best POSIX recommendedway is:

最后，逻辑条件写得不好。最好的POSIX 推荐方法是：

if [ -f $VAR1 ] && [ -f $VAR2 ] && [ -f $VAR3 ]

回答by cforbish

It looks like you only care about the hour so:

看起来你只关心小时，所以：

#!/bin/bash

while [ $(date +"%k") -gt 6 -a $(date +"%k") -lt 21 ];
do
  ##echo `php mainstatquery.php`
  echo "Hello World";
  sleep 5;
done

回答by cforbish

The ]that closes a [command must be a separate argument. Put a space before it.

所述]封闭一个[命令必须是一个单独的参数。在它之前放一个空格。