@:(在符号冒号处)在Makefile中是什么意思?

问题描述：

Makefile中的以下内容是什么?

What does the following do in a Makefile?

rule: $(deps)
    @:

我似乎无法在制作手册中找到它.

I can't seem to find this in the make manual.

答

这表示不要在输出中回显此命令".因此，此规则是说执行shell命令:，不要回显输出.

It means "don't echo this command on the output." So this rule is saying "execute the shell command : and don't echo the output.

当然，shell命令:是无操作的，因此它的意思是什么也不做，不要告诉."

Of course the shell command : is a no-op, so this is saying "do nothing, and don't tell."

为什么?

这里的窍门是，您将两种不同的语法混为一谈. make(1)语法是使用以@开头的动作，它只是不回显命令.像

The trick here is that you've got an obscure combination of two different syntaxes. The make(1) syntax is the use of an action starting with @, which is simply not to echo the command. So a rule like

always:
       @echo this always happens

不会发射

   echo this always happens
   this always happens

现在，规则的操作部分可以是 any shell命令，包括:. Bash帮助可以在任何地方对此进行解释:

Now, the action part of a rule can be any shell command, including :. Bash help explains this as well as anywhere:

$ help :
:: :
    Null command.

    No effect; the command does nothing.

    Exit Status:
    Always succeeds.

@:(在符号冒号处)在Makefile中是什么意思?

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