[yocto] explanation for ALTERNATIVE_LINK_NAME in ref manual seems incomplete

[Robert P. J. Day]

On Sun, 3 Nov 2013, Chris Larson wrote:

>
> On Sat, Nov 2, 2013 at 3:13 AM, Robert P. J. Day <rpjday at crashcourse.ca> wrote:
>        on my quest to spiff up the ref manual variables glossary, a question
>       about ALTERNATIVE_LINK_NAME, explained here:
>
>       http://www.yoctoproject.org/docs/latest/ref-manual/ref-manual.html#var-ALTERNATIVE_LINK_NAME
>
>        at first glance, that explanation *suggests* that the purpose of that
>       variable is to support an alternative name to an existing command, but
>       it doesn't make it clear that a *very* common usage is to simply
>       create a link with precisely the same name elsewhere. you see a *lot*
>       of this throughout the recipes (like this snippet from util-linux):
>
>       ALTERNATIVE_LINK_NAME[dmesg] = "${base_bindir}/dmesg"
>       ALTERNATIVE_LINK_NAME[kill] = "${base_bindir}/kill"
>       ALTERNATIVE_LINK_NAME[more] = "${base_bindir}/more"
>       ALTERNATIVE_LINK_NAME[mkswap] = "${base_sbindir}/mkswap"
>       ALTERNATIVE_LINK_NAME[blockdev] = "${base_sbindir}/blockdev"
>
>       which appears to simply create symlinks from /bin to programs in
>       /usr/bin, yes? (that's what it's doing, right?) i suspect it would be
>       useful to mention that application in the explanation, unless i'm
>       totally misunderstanding what i'm reading.
>
>
> I’m pretty sure that’s not the case. Afaik it creates a link from ALTERNATIVE_TARGET[name] to ALTERNATIVE_LINK_NAME[name]. If the target isn’t defined, iirc
> it defaults to adding a .${BPN} suffix to the link name. See lines 41 through 45 of update-alternatives.bbclass:
>
>     # NOTE: If ALTERNATIVE_TARGET is not defined, it will inherit the value
>     # from ALTERNATIVE_LINK_NAME.
>     #
>     # NOTE: If the ALTERNATIVE_LINK_NAME and ALTERNATIVE_TARGET are the same,
>     # ALTERNATIVE_TARGET will have '.{BPN}' appended to it.

  ok, i obviously didn't read that carefully enough, thanks.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

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