Shell Programming and Scripting

Hello, Please disregard my previous update when I said "it work". It didn;t, so the issue is still present for me. To avoid opening a new post, I will make a short recapitulation of the issue :

Background info :
Local machine : Linux, /bin/bash
Remote machine (for the user used for ssh) : SunOs, /bin/ksh
(so we have different OS, different Shells)

aaa_1=999
ssh -q user@machine "
> i=1
> echo aaa_1 is $aaa_1
> eval value=$`echo aaa_\${i}`
> echo value is \$value
> "
aaa_1 is 999
value is


So the variable $value is not set.
I've also tried the remote eval command this way:

Code:

eval value=\$`echo aaa_\${i}`
eval value=$`echo aaa_${i}`

With the same result.
So I basically want to create (while I'm in a remote ssh session) the variable value. $value should take the content of the variable aaa_1 (which was set in the initial session, before ssh).But I need to call the variable aaa_1 using variable $i (set after ssh and which has value "1" which will be used as part of variable aaa_1 name). I wanna use the value of $i variable to create the name of the $aaa_1 , and this name I wanna use in order to call the variable in the eval command.
The idea it;s a bit complicated but the code shouldn;t be hard to understand.

Any help regarding the syntax I use or different approach to accomplish what I want?

---------- Post updated at 05:38 AM ---------- Previous update was at 05:25 AM ----------

To be more clear, this is what I want but done in only one session , without ssh :

Code:

aaa_1=999
i=1
eval value=$`echo aaa_${i}`
echo "value is $value "
value is 999

So this way it works. The only difference is that I want

Code:

aaa_1=999

------------------------------------> to use ssh in this point

Code:

i=1
eval value=$`echo aaa_${i}`
echo "value is $value "
value is 999

@vbe (moderator) please read carefully my post before answering/suggesting something

THX,

You don't need an escape for i...

Code:

[root@bt] ssh localhost "
i=1
echo aaa_1 is $aaa_1
eval value=`echo \$aaa_${i}`
echo value is $value
"
aaa_1 is 999
value is 999

echo statement is redundant! eval value=\$aaa_${i}; also will work.

HTH
--ahamed

Nope... it didn;t work :

Code:

aaa=999
ssh -q user@remotehost "
> i=1
> echo aaa_1 is $aaa_1
> eval value=`echo \$aaa_${i}`
> echo value is $value
> "
aaa_1 is 999
value is

Nor this way :

Code:

aaa=999
ssh -q user@remotehost "
> i=1
> echo aaa_1 is $aaa_1
> eval value=\$aaa_${i}
> echo value is $value
> "
aaa_1 is 999
value is

Are you sure you got the posted results? could be be a shell discrepancy? as I said in background info I have different shells on local host and remote host. What's the situation on your side? what shells do you use ? I know that command lines are parsed differently by different shells.

---------- Post updated at 08:22 AM ---------- Previous update was at 08:09 AM ----------

btw: make sure you didn;t set the variable $value in the current shell. If you slipped by mistake the line
value=999
somwhere before the ssh , the results are wrong, because the value of $values is carried via ssh .
I've made that mistake before when I thought my problem is solved. :|

To get this right: you want to assign the content of a variable that is set on your localhost to another variable on a remote host and want to determine which local variable to use during the ssh-session? Sounds like bad design to me, but if that's your goal you need to transfer your variables to the remote host first.
Under the assumption that the possible variables to choose all start with aaa_ you could do it like this:

Code:

myset=$(set |grep "aaa_")
ssh -q user@remotehost "$myset; i=1; eval value='$'\$(echo aaa_\${i}); echo \$value"

The myset variable does the transfer. set returns the variable in reuseable form so $myset evaluates into all relevant variable-definitions.
Btw, if you like the backquote-notation better than the $()-one you have to escape the backquotes or command subsitution on your local host takes place.

Try this...

Code:

root@bt:~# ssh localhost "
i=1
echo aaa_1 is $aaa_1
eval value=\$aaa_$i
echo value is $value
"
aaa_1 is 999
value is 999

The above code was running on solaris... weird the same is not working on Linux...

--ahamed

Hello and many thanks. You craked it . it works perfectly for me with one small adjustment :
instead of

Code:

ssh -q user@remotehost "$myset; i=1; eval value='$'\$(echo aaa_\${i}); echo \$value"

I think it should be

Code:

ssh -q user@remotehost "eval $myset; i=1; eval value='$'\$(echo aaa_\${i}); echo \$value"

Indeed this is also a matter of shifting variables through ssh. I use it like this :
I have a config file on the local machine (with lots of defined variables e.g var1=88 ; var2=77 etc. ) I load the content of this file in a variable and then evaluate the content of this variables immediately after ssh (basically is exactly what you suggested but i don't use set | grep , I use a config file instead ).
I think of it as an elegant way to configure lots of things in one file on a single local machine. then to do lots of actions on many remote machines using the parts of config that you need pending by the conditions you find on each remote machine / situation.
do you suggest a general idea of a different approach?
Basically what I'm trying to do is a script to perform lots of network checks on and between many machines from one flow.