我无法使Makefile ifeq语法正常工作(检查文件的年龄) [英] I can't get Makefile ifeq syntax to work (checking age of a file)

问题描述

我正在尝试使用一个继承hack (已在起作用)，同时检查文件日期以创建一个一种可重用的，自动更新的基本makefile，多个项目可以从中继承；并使用 git pull 更新父Makefile，但是(这就是我遇到的问题)我只希望它每天尝试一次 git pull ，这样，在没有可用更新的机会几乎没有的情况下，等待git pull不会浪费很多时间.

I am attempting to use an inheritance hack (which is already working) along with checking a file date to create a sort of reusable, auto-updating base makefile from which multiple projects can inherit; and which will update the parent Makefile using a git pull, but (and this is where I'm stuck) I only want it to try the git pull once per day, so that it doesn't add up to a lot of wasted time waiting on a git pull when the chance of updates being available is almost nothing.

基本思想是:

baseMakefilePath=../../baseMakefile

do_some_work: .check-for-update
    @echo "working..."

.check-for-update:
    # is the file > 24 hours old?
    ifeq ( $(find . -mtime +24h -name '.check-makefile-update'), ./.check-makefile-update )
        @make .update
    else
        # if the file doesn't exist at all yet, pull the update
        ifeq ( $(find . -name '.check-makefile-update'), '' )
            @make .update
        else
            @echo "last update was recent, not updating..."
        endif
    endif

.update:
    cd $(baseMakefilePath) && git pull
    touch .check-makefile-update

我的理论是，通过使用 touch 更新 .check-makefile-update 文件上的修改时间戳，它应该每天仅运行一次git pull.

My theory is that by updating the modified timestamp on the .check-makefile-update file using touch it should only run the git pull once per day.

但是，我什至无法获得一个简单的 ifeq()有条件的工作条件:

However, I can't even get a dirt simple ifeq() conditional to work:

test:
    ifeq (a, a)
        @echo "a basic test works"
    else
        @echo "idunno"
    endif

有了这个基本的Makefile(注意:这是我测试时Makefile的唯一内容)，我得到此错误:

With this basic Makefile (note: this is the ONLY contents of the Makefile when I test it), I get this error:

$ make test
ifeq (a, a)
/bin/sh: -c: line 0: syntax error near unexpected token `a,'
/bin/sh: -c: line 0: `ifeq (a, a)'
make: *** [test] Error 2

如果我尝试运行第一个Makefile，则会得到相同的结果:

I get the same result if I try to run the first Makefile:

$ make do_some_work
# is the file > 24 hours old?
ifeq ( , ./.check-makefile-update )
/bin/sh: -c: line 0: syntax error near unexpected token `,'
/bin/sh: -c: line 0: `ifeq ( , ./.check-makefile-update )'
make: *** [.check-for-update] Error 2

我认为简化的示例表明发生了一些时髦的事情(或者我对ifeq的理解从根本上来说是有缺陷的)，但出于其价值，我还尝试用单引号和双引号引用了ifeq参数的各种组合.

I think the stripped down example shows that there's something funky going on (or my understanding of ifeq is fundamentally flawed) but for what it's worth, I also tried quoting various combinations of the ifeq arguments, with both single and double quotes.

我没有主意，但我觉得我对工作的解决方案很了解！我在做什么错了?

I'm out of ideas, but I feel like I'm sooo close to a working solution! What am I doing wrong?

如果有关系，我使用的是OSX 10.14.5，我的主shell是 zsh .这不是绝对要求，但是如果该解决方案也可以在Windows的现代版本(带有WSL)上运行，那就很好了.

If it matters, I'm on OSX 10.14.5, and my primary shell is zsh. It is not an absolute requirement but would be good if the solution can also run on modern versions of Windows (with WSL), too.

推荐答案

您对 ifeq 的理解从根本上是有缺陷的:)

Your understanding of ifeq is fundamentally flawed :)

makefile是两种不同语法的组合:makefile本身是用make语法编写的，而配方是用shell语法编写的.

A makefile is a combination of two different syntaxes: the makefile itself is written in make syntax, and the recipes are written in shell syntax.

这两种语法在任何方面都不兼容:编写配方时不能使用 make 语法，编写 makefile 时不能使用 shell 语法.

Those two syntaxes are not in any way compatible: you can't use make syntax when you are writing recipes and you can't use shell syntax when you are writing makefiles.

您怎么知道哪个?最简单的思考方法是，如果行中的第一个字符以TAB字符缩进，则它是shell语法，如果不是，则是make语法.现实更加微妙，但是规则永远是正确的.

How do you know which is which? The simplest way to think about it is that if the first character on your line is indented with a TAB character, it's shell syntax and if it's not, it's make syntax. The reality is more subtle but that rule is always true.

我确定您现在可以看到makefile出了什么问题以及为什么会出错:

I'm sure you can now see what's wrong with your makefile AND also why you get the errors you do:

test:
    ifeq (a, a)
        @echo "a basic test works"
    else
        @echo "idunno"
    endif

您正在尝试将make语法传递给shell.

you are trying to pass make syntax to the shell.

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