[U-Boot] [PATCH V2 4/4] cmd_part: add partition-related command

Tom Rini trini at ti.com
Fri Sep 7 00:45:36 CEST 2012

On 09/06/2012 11:46 AM, Stephen Warren wrote:
> On 09/06/2012 11:12 AM, Tom Rini wrote:
>> On Wed, Sep 05, 2012 at 08:38:26PM -0600, Stephen Warren wrote:
>>> On 09/05/2012 05:51 PM, Rob Herring wrote:
>>>> On 09/05/2012 05:03 PM, Stephen Warren wrote:
>>>>> From: Stephen Warren <swarren at nvidia.com>
>>>>> This implements the following:
>>>>> part uuid mmc 0:1
>>>>>   -> print partition UUID
>>>>> part uuid mmc 0:1 uuid
>>>>>   -> set environment variable to partition UUID
>>>> What's the reason to not always both print out and set the uuid env var?
>>>> Perhaps the env name should be partuuid or part_uuid as you could have
>>>> uuid's for other purposes?
>>> The idea is that if you're running the command interactively, you won't
>>> pass a variable name on the command-line, so the command will print out
>>> the UUID for you to read. In this case, it's pointless to set any
>>> environment variable.
>>> However, if you're writing a script, you want to capture the UUID into
>>> an environment variable, and it's quite unlikely you want to litter
>>> stdout with that content too. Hence, either-or, not both.
>> Do other commands have a "I'm being scripted, probably, don't stdout"
>> and "I'm being interactive, use stdout" distinction like this?  IMHO,
>> always printing out makes sense so you can "see" that your script is
>> working as you expect.
> In general, as a script writer, yes you do have the ability to choose.
> Typically, I'd write:
> part uuid ....
> vs.
> var=`part uuid ....`
> in order to control this. However, U-Boot's shell doesn't support
> backticks. As a script writer, I certainly desire the ability to control
> what commands spam to the console, and really don't think it's useful to
> print the UUID from a script (does the user really care, and any script
> developer can just echo it for debugging if they need it).
> I'm not aware of other U-Boot commands whose purpose it is to set
> environment variables, so can't really compare.
> Still, if you're insistent on this point, I can change the code to
> always print, and optionally write an environment variable.

No, you make a good point.  Thanks!


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