繼續翻譯

`.DEFAULT_GOAL' Sets the default goal to be used if no targets were specified onthe command line (*note Arguments to Specify the Goals: Goals.).The `.DEFAULT_GOAL' variable allows you to discover the currentdefault goal, restart the default goal selection algorithm byclearing its value, or to explicitly set the default goal. Thefollowing example illustrates these cases:# Query the default goal.ifeq ($(.DEFAULT_GOAL),)$(warning no default goal is set)endif.PHONY: foofoo: ; @echo $@$(warning default goal is $(.DEFAULT_GOAL))# Reset the default goal..DEFAULT_GOAL :=.PHONY: barbar: ; @echo $@$(warning default goal is $(.DEFAULT_GOAL))# Set our own..DEFAULT_GOAL := fooThis makefile prints:no default goal is setdefault goal is foodefault goal is barfooNote that assigning more than one target name to `.DEFAULT_GOAL' isillegal and will result in an error.

`.DEFAULT_GOAL'

設置如果在命令行中沒有制定目的場合，缺省的終點(*note Arguments to Specify the Goals :Goals)。

.DEFAULT_GOAL 變量允許你發現當前的缺省的終點，通過清除它的值來重新設置缺省的終點。下面的例子給出了如何操作：

# Query the default goal.
ifeq ($(.DEFAULT_GOAL),)
$(warning no default goal is set)
endif

.PHONY: foo
foo: ; @echo $@

$(warning default goal is $(.DEFAULT_GOAL))

# Reset the default goal.
.DEFAULT_GOAL :=

.PHONY: bar
bar: ; @echo $@

$(warning default goal is $(.DEFAULT_GOAL))

# Set our own.
.DEFAULT_GOAL := foo

這個 makefile 輸出:

no default goal is set
default goal is foo
default goal is bar
foo

請注意設置多余一個的目的名給`.DEFAULT_GOAL' 是無效的，會造成錯誤。

后文待續

本文轉自健哥的數據花園博客園博客，原文鏈接：http://www.cnblogs.com/gaojian/archive/2012/10/05/2712160.html，如需轉載請自行聯系原作者

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