Not able to set env var from anon function

Not able to set env var from anon function

[Nithyakala Sainath]

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Hello all,

I was playing with environmental variables and datastore that I fell into
this situation:

In a reccipe a.bb

export TEMPDIR = "temp"

python() {
        os.environ["TEMPDIR"] = "randomvalue"
}

do_compile() {
        echo ${TEMPDIR }
}

gives me "temp" as the answer. I was expecting "randomvalue". Can I not
modify the environmental variables and create new ones in anon functions ?

But d.setVar("TEMPDIR", "randomvalue") in place of os.environ does the
mgic. Why can't we manipulate the environmental variable using os.environ ?

In bitbake.conf, we see that we can get env vars using os.getenv.

Thanks,
Nithyakala.

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Re: Not able to set env var from anon function

[Burton, Ross]

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On 9 July 2015 at 13:12, Nithyakala Sainath <nithisai@gmail.com> wrote:

> But d.setVar("TEMPDIR", "randomvalue") in place of os.environ does the
> mgic. Why can't we manipulate the environmental variable using os.environ ?


Because in "echo ${TEMPDIR}" the variable is expanded by bitbake, not the
shell.  Use $TEMPDIR.

Ross

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Re: Not able to set env var from anon function

[Nithyakala Sainath]

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Thanks for your answer Ross.

But no, I already did that and tried again. The "randomvalue" is not
getting reflected. The variable still has "temp" in it.

Nithya.

On Thu, Jul 9, 2015 at 7:10 PM, Burton, Ross <ross.burton@intel.com> wrote:

>
> On 9 July 2015 at 13:12, Nithyakala Sainath <nithisai@gmail.com> wrote:
>
>> But d.setVar("TEMPDIR", "randomvalue") in place of os.environ does the
>> mgic. Why can't we manipulate the environmental variable using os.environ ?
>
>
> Because in "echo ${TEMPDIR}" the variable is expanded by bitbake, not the
> shell.  Use $TEMPDIR.
>
> Ross
>

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Re: Not able to set env var from anon function

[Richard Purdie]

On Thu, 2015-07-09 at 17:42 +0530, Nithyakala Sainath wrote:
> I was playing with environmental variables and datastore that I fell
> into this situation:
>
> In a reccipe a.bb
>
> export TEMPDIR = "temp"
>
> python() {
>         os.environ["TEMPDIR"] = "randomvalue"
> }
>
> do_compile() {
>         echo ${TEMPDIR } 
> }
>
> gives me "temp" as the answer. I was expecting "randomvalue". Can I
> not modify the environmental variables and create new ones in anon
> functions ?
>
> But d.setVar("TEMPDIR", "randomvalue") in place of os.environ does the
> mgic. Why can't we manipulate the environmental variable using
> os.environ ?
>
> In bitbake.conf, we see that we can get env vars using os.getenv.

bitbake tightly controls the task execution environment. Only variables
marked as "export" will be exported and the value used for them is that
from the datastore. Therefore, os.environ set in anonymous python will
simply get overwritten. You can't have one value in the datastore and
another in the environment.

As Ross points out, ${TEMPDIR} will get expanded by bitbake anyway so it
would print the datastore value anyway.

Cheers,

Richard

Re: Not able to set env var from anon function

[Nithyakala Sainath]

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Thanks Richard and Ross. That answers my question.

Nithya.

On Fri, Jul 10, 2015 at 1:38 PM, Richard Purdie <
richard.purdie@linuxfoundation.org> wrote:

> On Thu, 2015-07-09 at 17:42 +0530, Nithyakala Sainath wrote:
> > I was playing with environmental variables and datastore that I fell
> > into this situation:
> >
> > In a reccipe a.bb
> >
> > export TEMPDIR = "temp"
> >
> > python() {
> >         os.environ["TEMPDIR"] = "randomvalue"
> > }
> >
> > do_compile() {
> >         echo ${TEMPDIR }
> > }
> >
> > gives me "temp" as the answer. I was expecting "randomvalue". Can I
> > not modify the environmental variables and create new ones in anon
> > functions ?
> >
> > But d.setVar("TEMPDIR", "randomvalue") in place of os.environ does the
> > mgic. Why can't we manipulate the environmental variable using
> > os.environ ?
> >
> > In bitbake.conf, we see that we can get env vars using os.getenv.
>
> bitbake tightly controls the task execution environment. Only variables
> marked as "export" will be exported and the value used for them is that
> from the datastore. Therefore, os.environ set in anonymous python will
> simply get overwritten. You can't have one value in the datastore and
> another in the environment.
>
> As Ross points out, ${TEMPDIR} will get expanded by bitbake anyway so it
> would print the datastore value anyway.
>
> Cheers,
>
> Richard
>
>
>

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