moquery - use variables in -f parameter

[vv0bbLeS]

Hello all,

Does anyone know how to use variables in the -f parameter of moquery ?

For example, say I have defined a variable nodeId="paths-292" and am trying to use it. I have tried all the following with no luck.

I suspect it is some weirdness as the -f argument has to be in double-quotes, but the nodeId is already defined as a string :

apic1# nodeId="paths-292"
apic1# 
apic1# 
apic1# 
apic1# 
apic1# moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*"$nodeId"' 
No Mos found
apic1# 
apic1# 
apic1# moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*"${nodeId}"'
No Mos found
apic1# 
apic1# 
apic1# moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*$nodeId' 
Error: no valid token found at (1, 21) '$nodeId'
apic1# 
apic1# 
apic1# moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*${nodeId}' 
Error: no valid token found at (1, 21) '${nodeId}'
apic1# 
apic1# 

If I use the regular string paths-292 in the -f parameter instead of the variable, I get results so I know there are MO's that fit the query.

If anyone has any ideas how to use variables in the -f parameter of moquery, let me know! Thanks!

[RedNectar · Accepted solution]

Hi @vv0bbLeS ,

By now you are hoping someone wh really knows this stuff will answer you, not just me

BUT I really do think there are problems with the-f parameter of moquery but that aside, I thought I'd at least get you wasting some more time trying to figure it out with a short lesson on the intricicies of quoting in bash

The problem you are battling with in the examples about is that a single quoted string is always literal in bash, so the $nodeID variable is not going to get expanded using single quotes.

So the command:

moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*"paths-292"' 

will work for you because the string:

fv.RsCEpToPathEp.dn*"paths-292"

(including the quotes) gets passed to the -f filter

The problem is that if you replace the paths-292 with $nodeId (or ${nodeId}) it will get passed literally - as 

fv.RsCEpToPathEp.dn*"$nodeId"

The good new is that the -f parameter is happy with double quotes - but you still need to keep the expanded variable in quotes.

Enter the escapre character - backslash \

This means you COULD enter the command 

moquery -c fvRsCEpToPathEp -f 'fv.RsCEpToPathEp.dn*"paths-292"'

as

moquery -c fvRsCEpToPathEp -f "fv.RsCEpToPathEp.dn*\"paths-292\""

by "escaping" the embedded quotes.

And this will also work with variables - so in your example where you set nodeId to "paths-292", the following will work exactly the same way:

moquery -c fvRsCEpToPathEp -f "fv.RsCEpToPathEp.dn*\"${nodeId}\""

I was tempted to add a variable for "up" and "down" when I replied to your previous post, but thought the escaping syntax made it too hard - but then you went and dived into awk (which is a minefield in itself)

Anyway - I hope you come up with a better answer - make sure you share it if you do

[vv0bbLeS]

@RedNectar  I think you know plenty about ACI! I was figuring by now folks would be hoping I would quit clogging the forum with these trivial questions!

And ah yes, the single quotes, I'm not sure how I missed that. PowerShell is the same way if you've ever coded in it, it treats single quotes as string literals, which of course can be useful but can also be a huge pain. ( Python of course doesn't make that quote-type distinction ).

I think your solution of just using 2 pairs of double quotes and escaping the "inner" double quotes is a good solution. For fun I tried expanding on your idea by having 2 variables and nesting them, e.g. nodeId and nodeIdStr , with nodeId being something simple like "292" and nodeIdStr being the actual string with escaped quotes in it. My plan was that if I needed to change the node ID value I could just edit the easier variable nodeId, but it doesn't look like ACI dynamically changes nested variables (unless I'm missing something, which is entirely possible):

apic1# nodeId="292" 
apic1# 
apic1# 
apic1# nodeIdStr="\"paths-${nodeId}\"" 
apic1# 
apic1# 
apic1# print ${nodeIdStr}
"paths-292"
apic1# 
apic1# 
apic1# nodeId="291"
apic1# 
apic1# 
apic1# print ${nodeIdStr}
"paths-292"
apic1# 

 So, from my testing, it would be best to just stick to the one variable, e.g. "paths-292" and, per your solution above, include the single variable with escaped double-quotes in the -f parameter. Thanks again!

[RedNectar]

I think what you are trying to achieve can be done like this:

nodeId="291"
moquery -c fvRsCEpToPathEp -f "fv.RsCEpToPathEp.dn*\"paths-${nodeId}\""

nodeId="292"
moquery -c fvRsCEpToPathEp -f "fv.RsCEpToPathEp.dn*\"paths-${nodeId}\""

[vv0bbLeS]

@RedNectar  yes sir, i was just trying to nest variable assignments to see if it would work, but I discovered you would have to reassign each variable anytime you wanted to change them as ACI doesn't dynamically update variables that contain nested variables as part of them. Fun times!