Support -g option to dump value string only (no key string, no quotes).

Support -g option to dump value string only (no key string, no quotes, no newline).

Added filter for exporting. Also added an export type for exporting value only.

Refined some comments too.

Change-Id: I97fdd408bd444094ccc3378564b37c252fcf213e

R=hungte@chromium.org,dhendrix@chromium.org
BUG=no bug id
TEST=Compile okay on Z600 and x86-*. Tested on Z600 machine:
vpd -f test  -s ABC=DEF -s DEF=GHI -s IJK=ABC
vpd -f test -l  # all show up
vpd -f test -g abc  # nothing shows up
vpd -f test -g ABC  # DEF is showed.
vpd -f test -l -g  # error check: need an argument for -g
vpd -f test -l -g XXX  # error check: -g and -l must be mutually exclusive.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=65f4104

[Hung-Te, 2011-04-14 10:12:33]

LGTM

P.S: I think we won't want to put multiple key names or regex into -g, because
there's no way to distinguish from the continuous output. People who wants a
fuzzy search should get all values and parse by himself.

You can simplify the code by making it as simple "get" if you wish, but I'm OK
if you want to keep current implementation - that also looks good to me.

[Louis, 2011-04-15 02:28:27]

Thanks for review. My intention is for people to easily enumerate similar
fields, for example, "^.*_MAC$" to list ethernet/wifi/bluetooth MAC addresses in
one command.

Code submitted. Will implement that when real use case comes.

On 2011/04/14 10:12:33, Hung-Te wrote:
> LGTM
> 
> P.S: I think we won't want to put multiple key names or regex into -g, because
> there's no way to distinguish from the continuous output. People who wants a
> fuzzy search should get all values and parse by himself.
> 
> You can simplify the code by making it as simple "get" if you wish, but I'm OK
> if you want to keep current implementation - that also looks good to me.