use POSIX parameter expansion for assigning default values #202

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1. guysoft commented on Aug 31, 2023

   

   guysoft

   on Aug 31, 2023

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   So it would be in the config file:

   BASE_IMAGE_RASPBIAN=${BASE_RELEASE_COMPRESS:=yes}

   ?

   I want to assign default values there because its also where people go to look what they can set.
2. umlaeute commented on Aug 31, 2023

   

   umlaeute

   on Aug 31, 2023

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   i'm not sure what you mean.
   your example would

   1. set BASE_RELEASE_COMPRESS to yes unless it is already set to a non-empty value
   2. set BASE_IMAGE_RASPBIAN to the value of BASE_RELEASE_COMPRESS (from item1)

   i guess that mixing of BASE_IMAGE_RASPBIAN and BASE_RELEASE_COMPRESS was just a typo.

   my line:

   : ${BASE_RELEASE_COMPRESS:=yes}

   does:

   1. set BASE_RELEASE_COMPRESS to yes unless it is already set to a non-empty value
   2. nothing else (as : is a nop-command)

   you can of course use variables on the right-hand term as well:

   : ${BASE_IMAGE_PATH:=${DIST_PATH}/image}

   but if you feel that this is just busy-work, feel free to ignore (and possibly close) this ticket