[yocto] which yocto doc explains bitbake assignment variations?
Mark Hatle
mark.hatle at windriver.com
Thu Mar 29 14:55:22 PDT 2012
On 3/29/12 4:47 PM, Robert P. J. Day wrote:
>
> somewhere, i'm assuming there's a decent explanation of the
> different bitbake assignment variations (=, ?=, ??=), but i don't
> immediately see it, and i think it's pretty important that that's
> explained properly. pointer?
>
> rday
>
The bitbake manual has this information in it. I don't know of a current
version that is posted online, but you should be able to generate it from within
bitbake itself.
(and older version: http://docs.openembedded.org/bitbake/html/)
But for the record the variations:
Immediate, overwrite existing values:
variable = "value"
Conditional, only if not previously set:
variable ?= "value"
Conditional, late evaluation -- i.e. at the end, only if set:
variable ??= "value"
Immediate, expand variables immediately:
variable := "${value}"
Append with spaces:
variable += "value"
Prepend with spaces:
variable =+ "value"
Append without spaces:
variable .= "value"
Prepend without spaces:
variable =. "value"
Append "late" evaluation:
variable_append = "value"
--Mark
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