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

[Bob Eager]

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

> Hi,
> 
> [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?="?

As it says in the man page...

  "Assign the value to the variable if it is not already defined"