How can I save U-Boot env vars to HUSH shell vars.
I'd like to store the values of environment variables in HUSH shell variables and then restore them later. My ultimate goal is to preserve a few environment variables through a "env default -f".
I'm working with U-Boot 2010.12. Changing to a newer version is not possible at this time.
I realize this is a very old U-Boot. I'm hoping that the relevant parts of U-Boot have not changed between that old version and versions you might provide help for.
I tried a few things and haven't found the right combination. I think the following commands demonstrate my problem.
Given the U-Boot commands
=> setenv e "e ethaddr ipaddr rootpath"
=>
=> printenv e ethaddr ipaddr rootpath
e=e ethaddr ipaddr rootpath
ethaddr=00:00:17:88:09:36
ipaddr=10.3.134.80
rootpath=/home/anyuser/a/device/tr/rootfs
=>
=> for i in $e; do v_$i=$i; done
=>
What I get:
=> showvar
HUSH_VERSION=0.01
v_e=e
v_ethaddr=ethaddr
v_ipaddr=ipaddr
v_rootpath=rootpath
=>
What I want:
=> showvar
HUSH_VERSION=0.01
v_e=e ethaddr ipaddr rootpath
v_ethaddr=00:00:17:88:09:36
v_ipaddr=10.3.134.80
v_rootpath=/home/anyuser/a/device/tr/rootfs
=>
So, how do I re-write the for loop to get the desired results
Thanks for any help,
Jim
Signature · 3 lines
Jim Chargin AJA Video Systems jimc at aja.com (530) 271-3334 http://www.aja.com
Dear James,
Quoted 3 lines · In message <[email protected]> you wrote:
I'd like to store the values of environment variables in HUSH shell variables and then restore them later. My ultimate goal is to preserve a few environment variables through a "env default -f".
It is probably easier to use "env export" to store this set of variables to some area in memory. You could even make this permanent by writing it to flash or some storage device.
Quoted 2 lines
I'm working with U-Boot 2010.12. Changing to a newer version is not possible at this time.
Heh. As soon as you have to change _any_ code, you can as well upgrade.
Quoted 3 lines
I realize this is a very old U-Boot. I'm hoping that the relevant parts of U-Boot have not changed between that old version and versions you might provide help for.
Well, a ton of bug fixes and improvements have been added since. One of the extensions you want and which has been added only after v2010.12 is the capability to export only a sub-set of the environment (i. e. a list of variables passed on the command line).
Quoted 1 line
=> for i in $e; do v_$i=$i; done
...
Quoted 1 line
What I get:
...is exactly what you coded. You would get the same in any other shell, too.
Quoted 9 lines
=> showvar
HUSH_VERSION=0.01
v_e=e ethaddr ipaddr rootpath
v_ethaddr=00:00:17:88:09:36
v_ipaddr=10.3.134.80
v_rootpath=/home/anyuser/a/device/tr/rootfs
=>So, how do I re-write the for loop to get the desired results
This would require an "eval" or command substitution, which we do not have in our implementation of the hush shell.
To me it seems the easiest way to get what you want is to use "env export ... ethaddr ipaddr rootpath" or similar.
Um... yes, this requires an update to more recent code.
Best regards,
Wolfgang Denk
Signature · 4 lines
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de Of course there's no reason for it, it's just our policy.
Dear Wolfgang,
Thank you for your reply.
Quoted 10 lines · Wolfgang Denk
Dear James,
Quoted 3 lines · In message <[email protected]> you wrote:
I'd like to store the values of environment variables in HUSH shell variables and then restore them later. My ultimate goal is to preserve a few environment variables through a "env default -f".
It is probably easier to use "env export" to store this set of variables to some area in memory. You could even make this permanent by writing it to flash or some storage device.
I hadn't thought of exporting the environment to memory, excellent idea.
Quoted 6 lines
Quoted 3 lines
I'm working with U-Boot 2010.12. Changing to a newer version is not possible at this time.
Heh. As soon as you have to change _any_ code, you can as well upgrade.
I was hoping (in vain perhaps) to do my work modifying only the environment.
Quoted 10 lines
Quoted 4 lines
I realize this is a very old U-Boot. I'm hoping that the relevant parts of U-Boot have not changed between that old version and versions you might provide help for.
Well, a ton of bug fixes and improvements have been added since. One of the extensions you want and which has been added only after v2010.12 is the capability to export only a sub-set of the environment (i. e. a list of variables passed on the command line).
This is a definite drawback to having an old U-Boot; I'm sure I would benefit from the bug fixes and other enhancements.
Exporting a list of values sounds like a nice addition that would be helpful to me.
Quoted 15 lines
Quoted 1 line
=> for i in $e; do v_$i=$i; done
...
Quoted 1 line
What I get:
...is exactly what you coded. You would get the same in any other shell, too.
Quoted 8 lines
=> showvar
HUSH_VERSION=0.01
v_e=e ethaddr ipaddr rootpath
v_ethaddr=00:00:17:88:09:36
v_ipaddr=10.3.134.80
v_rootpath=/home/anyuser/a/device/tr/rootfs
=>
Quoted 5 lines
Quoted 1 line
So, how do I re-write the for loop to get the desired results
This would require an "eval" or command substitution, which we do not have in our implementation of the hush shell.
"eval" seemed to me also to be what I wanted. I'm aware it isn't present in hush, but I was hoping for some magic from the community. :-)
Quoted 3 lines
To me it seems the easiest way to get what you want is to use "env export ... ethaddr ipaddr rootpath" or similar.
I suppose, with my 2010.12, I could export everything to memory and then parse through it to find the values I need then import them. Sounds vaguely possible but it's probably more complex than doing the U-Boot upgrade.
Quoted 1 line
Um... yes, this requires an update to more recent code.
Yes, update is on my to-do list, but schedules dictate that the upgrade is not my first priority. The conclusion reached here adds to the argument for doing it sooner rather than later.
Quoted 5 lines
Best regards,
Wolfgang Denk
Thank you again for you comments.
Jim
Dear James,
Quoted 5 lines · In message <[email protected]> you wrote:
Quoted 3 lines
Heh. As soon as you have to change _any_ code, you can as well upgrade.
I was hoping (in vain perhaps) to do my work modifying only the environment.
Yes, I understand this. But I have to admit that I don't see an easy way.
Hm... thinking about it, you _can_ do this, but it's a bit ugly...
POC code:
=> print ethaddr ipaddr serverip ethaddr=00:10:ec:01:08:84 ipaddr=192.168.100.6 serverip=192.168.1.1 => echo E=$foo_ethaddr I=$foo_ipaddr S=$foo_serverip E= I= S= => setenv setvar 'setenv tmp "foo_$arg=$$arg"' => for arg in ethaddr ipaddr serverip ; do > run setvar > run tmp > echo E=$foo_ethaddr I=$foo_ipaddr S=$foo_serverip > done E=00:10:ec:01:08:84 I= S= E=00:10:ec:01:08:84 I=192.168.100.6 S= E=00:10:ec:01:08:84 I=192.168.100.6 S=192.168.1.1
As you can see, I'm useing a two-step approach to first constuct a command and then to run it. This "consumes" 2 environment variables ("tmp" and "arg"), but this should be an acceptable price...
Quoted 2 lines
This is a definite drawback to having an old U-Boot; I'm sure I would benefit from the bug fixes and other enhancements.
Yes.
Quoted 2 lines
Exporting a list of values sounds like a nice addition that would be helpful to me.
The new env command allows for a lot of interesting features, like maintaining a set of "user profiles", i. e. independent sets of environment settings which can be loaded and restored as you lik, including things like perfoming a "reset to factory defaults" (which still can be changed, i. e. you can update the factory default settings and are not limited to the fixed compiled in default env values.
Quoted 4 lines
I suppose, with my 2010.12, I could export everything to memory and then parse through it to find the values I need then import them. Sounds vaguely possible but it's probably more complex than doing the U-Boot upgrade.
You don't have enough tools in the shell to do this parsing by any scripts, so you would need code. And if you add new code, you change the binary anyway, so you could upgrade as well.
Best regards,
Wolfgang Denk
Signature · 7 lines
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"I knew then (in 1970) that a 4-kbyte minicomputer would cost as much
as a house. So I reasoned that after college, I'd have to live
cheaply in an apartment and put all my money into owning a computer."
- Apple co-founder Steve Wozniak, EE Times, June 6, 1988, pg 45Dear Wolfgang,
With your help, I have satisfied my need.
Quoted 35 lines · Wolfgang Denk
Dear James,
Quoted 5 lines · In message <[email protected]> you wrote:
Quoted 3 lines
Heh. As soon as you have to change _any_ code, you can as well upgrade.
I was hoping (in vain perhaps) to do my work modifying only the environment.
Yes, I understand this. But I have to admit that I don't see an easy way.
Hm... thinking about it, you _can_ do this, but it's a bit ugly...
POC code:
=> print ethaddr ipaddr serverip ethaddr=00:10:ec:01:08:84 ipaddr=192.168.100.6 serverip=192.168.1.1 => echo E=$foo_ethaddr I=$foo_ipaddr S=$foo_serverip E= I= S= => setenv setvar 'setenv tmp "foo_$arg=$$arg"' => for arg in ethaddr ipaddr serverip ; do > run setvar > run tmp > echo E=$foo_ethaddr I=$foo_ipaddr S=$foo_serverip > done E=00:10:ec:01:08:84 I= S= E=00:10:ec:01:08:84 I=192.168.100.6 S= E=00:10:ec:01:08:84 I=192.168.100.6 S=192.168.1.1
Quoted 3 lines
As you can see, I'm useing a two-step approach to first constuct a command and then to run it. This "consumes" 2 environment variables ("tmp" and "arg"), but this should be an acceptable price...
Extending this a bit further to include yet another env var, I have the following that allows a list to be saved and restored.
=> setenv setvar 'setenv tmp "v_$arg=$$arg"'
=> setenv usevar 'setenv t v_$arg;setenv tmp "setenv $arg $$t"' =>
And testing these:
=> setenv list "ipaddr ethaddr list" => printenv ipaddr ethaddr ipaddr=10.3.134.80 ethaddr=00:00:17:88:09:36 => => # to save => for arg in $list; do run setvar; run tmp; done => showvar HUSH_VERSION=0.01 arg=list v_ipaddr=10.3.134.80 v_ethaddr=00:00:17:88:09:36 v_list=ipaddr ethaddr list => => # simulate "env default -f" => setenv ethaddr; setenv ipaddr; setenv list => => # to restore (note use of v_list rather than list) => for arg in $v_list; do run usevar; run tmp; done => printenv ipaddr ethaddr list ipaddr=10.3.134.80 ethaddr=00:00:17:88:09:36 list=ipaddr ethaddr list =>
Perhaps this isn't as nice looking as it could be. But, it does solve the problem at hand, which has value for me. The solution boils down to two definitions in the default environment (setvar and usevar) and then a single script line to save the values and another single script line to restore them. I don't consider this addition burdensome at all.
And to paraphrase a former US Sec Def, "You code with the tools you have rather than with the tools you might like to have."
Setting temporaries to commands that are then executed as a means to getting evaluations done when needed seems like a great addition to the "bag of tricks"
Quoted 3 lines
...
The new env command allows for a lot of interesting features, ...
I look forward to using these new facilities.
And, I appreciate you help very much.
Best regards,
Jim
Signature · 3 lines
Jim Chargin AJA Video Systems jimc at aja.com (530) 271-3334 http://www.aja.com
Dear James,
Quoted 2 lines · In message <[email protected]> you wrote:
With your help, I have satisfied my need.
I'm happy that I was able to help.
Thanks for the summary and your actual code.
Quoted 1 line
And, I appreciate you help very much.
You are welcome.
Best regards,
Wolfgang Denk
Signature · 4 lines
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de God made the integers; all else is the work of Man. - Kronecker