blocks|key|1033186|text|您可以使用ifdef而不是其他目标。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1033187|.PHONY:+deploy
deploy:
++++ifdef+ENV
++++++++rsync+.+$(ENV).example.com:/var/www/myapp/
++++else
++++++++@echo+1>&2+"ENV+must+be+set"
++++++++false++++++++++++++++++++++++++++#+Cause+deploy+to+fail
++++endif|code-block|syntax|javascript|1033188|entityMap^0|5|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

You can use <code>ifdef</code> instead of a different target.

<pre><code>.PHONY: deploy
deploy:
 ifdef ENV
 rsync . $(ENV).example.com:/var/www/myapp/
 else
 @echo 1&gt;&amp;2 "ENV must be set"
 false # Cause deploy to fail
 endif
</code></pre>

blocks|key|1033295|text|正如我所看到的，命令本身需要ENV变量，所以您可以在命令本身中检查它：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1033296|.PHONY:+deploy+check-env

deploy:+check-env
++++rsync+.+$(ENV).example.com:/var/www/myapp/

check-env:
++++if+test+"$(ENV)"+=+""+;+then+\
++++++++echo+"ENV+not+set";+\
++++++++exit+1;+\
++++fi|code-block|syntax|javascript|1033297|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

As I see the command itself needs the ENV variable so you can check it in the command itself:

<pre><code>.PHONY: deploy check-env

deploy: check-env
 rsync . $(ENV).example.com:/var/www/myapp/

check-env:
 if test "$(ENV)" = "" ; then \
 echo "ENV not set"; \
 exit 1; \
 fi
</code></pre>

blocks|key|1033377|text|您可以创建一个隐式保护目标，用于检查是否定义了词干中的变量，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1033378|guard-%25:
++++@+if+[+"${${*}}"+=+""+];+then+\
++++++++echo+"Environment+variable+$*+not+set";+\
++++++++exit+1;+\
++++fi|code-block|syntax|javascript|1033379|然后，将guard-ENVVAR目标添加到要断言定义了变量的任何位置，如下所示：|offset|length|style|CODE|1033380|change-hostname:+guard-HOSTNAME
++++++++./changeHostname.sh+${HOSTNAME}|1033381|如果您调用make+change-hostname，而没有在调用中添加HOSTNAME=somehostname，那么您将得到一个错误，并且构建将失败。|1033382|entityMap^0|0|0|4|C|0|0|5|K|Z|L|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

You can create an implicit guard target, that checks that the variable in the stem is defined, like this:
<pre><code>guard-%:
 @ if [ &quot;${${*}}&quot; = &quot;&quot; ]; then \
 echo &quot;Environment variable $* not set&quot;; \
 exit 1; \
 fi
</code></pre>
You then add a <code>guard-ENVVAR</code> target anywhere you want to assert that a variable is defined, like this:
<pre><code>change-hostname: guard-HOSTNAME
 ./changeHostname.sh ${HOSTNAME}
</code></pre>
If you call <code>make change-hostname</code>, without adding <code>HOSTNAME=somehostname</code> in the call, then you'll get an error, and the build will fail.

blocks|key|1033458|text|到目前为止，给定答案的一个可能问题是make中的依赖顺序没有定义。例如，运行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1033459|make+-j+target|code-block|syntax|javascript|1033460|当target有几个依赖项时，不能保证这些依赖项将以任何给定的顺序运行。|offset|length|style|CODE|1033461|这个问题的解决方案(确保在选择食谱之前检查ENV+)是在make的第一次遍历期间检查ENV，而不是任何食谱：|1033462|##+Are+any+of+the+user's+goals+dependent+on+ENV?
ifneq+($(filter+deploy+other-thing-that-needs-ENV,$(MAKECMDGOALS)),$())
ifndef+ENV+
$(error+ENV+not+defined)
endif
endif

.PHONY:+deploy

deploy:+foo+bar
++++...

other-thing-that-needs-ENV:+bar+baz+bono
++++...|1033463|你可以读到使用here的不同函数/变量，而$()只是明确声明我们正在与"nothing“进行比较的一种方式。|1033464|entityMap|0|LINK|mutability|MUTABLE|url|http://www.gnu.org/software/make/manual/html_node/Quick-Reference.html^0|0|0|1|6|0|0|0|L|3|7|4|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@$I|13|J|14|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|17|8|@$I|18|J|19|K|L]]|9|@$I|1A|J|1B|1|1C]]|A|$]]|$1|S|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

One possible problem with the given answers so far is that dependency order in make is not defined. For example, running:

<pre><code>make -j target
</code></pre>

when <code>target</code> has a few dependencies does not guarantee that these will run in any given order.

The solution for this (to guarantee that ENV will be checked before recipes are chosen) is to check ENV during make's first pass, outside of any recipe:

<pre><code>## Are any of the user's goals dependent on ENV?
ifneq ($(filter deploy other-thing-that-needs-ENV,$(MAKECMDGOALS)),$())
ifndef ENV 
$(error ENV not defined)
endif
endif

.PHONY: deploy

deploy: foo bar
 ...

other-thing-that-needs-ENV: bar baz bono
 ...
</code></pre>

You can read about the different functions/variables used <a href="http://www.gnu.org/software/make/manual/html_node/Quick-Reference.html" rel="noreferrer">here</a> and <code>$()</code> is just a way to explicitly state that we're comparing against "nothing".

A Makefile <code>deploy</code> recipe needs an environment variable <code>ENV</code> to be set to properly execute itself, whereas other recipes don't care, e.g.,
<pre><code>ENV = 

.PHONY: deploy hello

deploy:
 rsync . $(ENV).example.com:/var/www/myapp/

hello:
 echo &quot;I don't care about ENV, just saying hello!&quot;
</code></pre>
How can I make sure this <code>ENV</code> variable is set? Is there a way to declare this makefile variable as a prerequisite of the deploy recipe? e.g.,
<pre><code>deploy: make-sure-ENV-variable-is-set
</code></pre>

How to ensure Makefile variable is set as a prerequisite?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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Makefile deploy配方需要设置环境变量ENV来正确地执行它自己，而其他配方并不关心，例如，ENV = .PHONY: deploy hellodeploy:    rsync . $(ENV).example.com:/var/www/myapp/hello:    echo "I don't care a...

问如何确保Makefile变量被设置为先决条件？
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