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klingtnet/gnumake-environment-variable-conditional.md

Last active January 12, 2017 11:38
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GNU Make: Branch if an environment variable is set
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gnumake-environment-variable-conditional.md 
.PHONY: all

ifdef IFSETUSEMYVALUE
FOO:=$(IFSETUSEMYVALUE)
else
FOO:="another value"
endif

all:
  @echo $(FOO)
$ make
another value
$ IFSETUSEMYVALUE="Hi" make
Hi

Note: Variable assignments with colon equal (:=) will be expanded only once, whereas = assignments are expanded on each use.

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