How to assign the output of a command in variable in shell script and use it conditionally

Question

I am trying to write some conditional script to up my kubernetes system

#!/bin/sh

#checking if the namespace exists
export namespace="kube-system"
export mypassword="logan"
#installing json reader
echo mypassword | sudo apt-get install jq
echo mypassword | status=$(sudo kubectl get ns ${namespace} -o json | jq .status.phase -r)
echo "$status" #its not printing

if [ "$status" = "Active" ]
then
   echo hi
else
  echo bye
fi

But some how my status variable is not getting printed and neither the if else condition is working ,how to solve it ?Please help

Btw.: I suggest to replace `echo mypassword` with `echo "$mypassword"`. — Cyrus, May 21 '22 at 10:07

score 2 · Answer 1 · edited May 21 '22 at 10:06

2

Your status assignment (status=$(...)) is happening in a subprocess (the one forked to receive the output of echo mypassword). So any changes wont reach the running shell.

You need something like:

# execute a command in a subprocess and capture all output in `status`
status=$(echo ... | sudo kubectl ... | jq ...)
if [ "$status" == 'active' ]
then
   echo 'active'
else
   echo 'not active'
fi

edited May 21 '22 at 10:06

Cyrus

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answered May 21 '22 at 09:51

Michail Alexakis

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Ohh ok ,so how to solve this ? – john doe May 21 '22 at 09:53
@Cyrus, you quoted the variable $status so that test doesnt break if status is an empty string or is unset, is that right? – Michail Alexakis May 21 '22 at 10:10
Yes, and to prevent problems when $status contains a string with enclosed spaces (`bash: [: too many arguments`). – Cyrus May 21 '22 at 10:16
@Cyrus, you are absolutely right; i just thought status would be some enumeration (C identifier-like) string – Michail Alexakis May 21 '22 at 10:40
Note that one higher level "correct" solution is to stop passing passwords to sudo. Configure sudo so that is not necessary, or run the entire script via sudo. – William Pursell May 21 '22 at 13:47
Minor detail: since the original script uses `#!/bin/sh` rather than `#!/bin/bash`, the single `=` should be used rather than `==` as the argument to `[`. `==` is a bashism. – William Pursell May 21 '22 at 14:08

score 0 · Answer 2 · answered May 21 '22 at 12:45

You could as well test the value with jq directly. When given the -e option, jq turns boolean values to exit status.

echo "$mypassword" | sudo kubectl get ns "$namespace" -o json | 
if jq -e '.status.phase == "Active"' >/dev/null
then
  echo hi
else
  echo bye
fi

How to assign the output of a command in variable in shell script and use it conditionally

2 Answers2