Makefile, ${VARIABLE}= vs. ${VARIABLE}?=

Gary Jennejohn gljennjohn at googlemail.com
Sun Feb 13 14:57:52 UTC 2011


On Sun, 13 Feb 2011 14:14:17 +0000 (UTC)
"Helmut Schneider" <jumper99 at gmx.de> wrote:

> [helmut at BSDHelmut ~]$ grep -ir latest /usr/ports/www/apache2?
> /usr/ports/www/apache20/Makefile:LATEST_LINK=   apache20
> /usr/ports/www/apache22/Makefile:LATEST_LINK?=  apache22
> [helmut at BSDHelmut ~]$
> 
> So, what's the difference between e.g. "LATEST_LINK=" and
> "LATEST_LINK?="?
> 

from make(1)

=       Assign the value to the variable.  Any previous value is overrid-
        den.

?=      Assign the value to the variable if it is not already defined.

-- 
Gary Jennejohn


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