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Environment variable substitution in Linux make


 
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# 1  
Old 07-08-2015
Environment variable substitution in Linux make

I know that I can do this in bash
Code:
ver=${VERSION:-$DEFVERSION}

so ver is $VERSION if it's set but $DEFVERSION if $VERSION isn't set

I want to do the same thing as a macro in a Makefile and can't get it to work - maybe something like...
Code:
VER=$(shell ${$(VERSION):-$(DEFVERSION)})

Any help appreciated
# 2  
Old 07-08-2015
You can use the ?= operator, which sets a variable if and only if it's not already set:

Code:
VAR ?= value

 

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