Dear Rasmus,
In message <[email protected]> you wrote:
>
> So in bash, that might be written
>
> slot=none
> for x in $BOOT_ORDER ; do
> eval "left=\${BOOT_${x}_LEFT}"
> if [ $left -gt 0 ] ; then
> slot=$x
> break
> fi
> done
OK, now I get the context.
You mean something like this in U-Boot ?
setenv BOOT_ORDER A B C D
setenv BOOT_A_LEFT 0
setenv BOOT_B_LEFT 0
setenv BOOT_C_LEFT 2
setenv BOOT_D_LEFT 5
slot=none
for i in $BOOT_ORDER ; do
setenv tmp_cmd 'setexpr tmp_val sub '^' "" $'BOOT_${i}_LEFT
run tmp_cmd
test $slot = none && test $tmp_val -gt 0 && slot=$i
done
echo "## Chosen Slot = $slot"
This returns
## Chosen Slot = C
as you want. The only inelegance of this approach is that it will
also print
tmp_val=0
tmp_val=0
tmp_val=2
tmp_val=5
on the console, which is not really nice. I wonder if it's worth
adding a "-q" flag to the setexpr sommand?
And - I even beat your bash script which has 8 lines, while my
script has only 6 :-) :-)
> Now we can work around the lack of break in the busybox shell by writing
> the loop so that the main body is skipped if we've found a valid slot:
Things like this are usually easier done using && and ||
> But we still can't translate this to busybox shell, because there's no
> eval. Now, I can do this with a hypothetical "env get" command which I
> just implemented to test that it works, and then the above becomes
There is no eval, but there is still a zillion of simple tricks you
can pull to get your stuff done :-)
> Now, if you can implement the line marked #magic with existing
> functions, I'm all ears. Or if you can implement the semantics of this
> snippet in some other way, which does not open-code explicit references
> to BOOT_A_LEFT, BOOT_B_LEFT etc. This is what I meant when I said I'd
> prefer not to write the loop like this:
See above...
> [yes, I also want left set as a side effect to the current value of the
> appropriate BOOT_x_LEFT].
Oh, this is a new requirement...
So lets change my little script to add setting "left":
slot=none
for i in $BOOT_ORDER ; do
setenv tmp_cmd 'setexpr tmp_val sub '^' "" $'BOOT_${i}_LEFT
run tmp_cmd
test $slot = none && test $tmp_val -gt 0 && slot=$i && left=$tmp_val
done
echo "## Chosen Slot = $slot ; Left = $left"
Result:
## Chosen Slot = C ; Left = 2
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
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