template parsing error: template: :1: unexpected "=" in operand

Question

template parsing error: template: :1: unexpected "=" in operand

I got the above error when executing the below command in Windows,

docker inspect --format="{{range $key, $value := .Config.Env}}{{if eq (index (split $value "=") 0) "VERSION"}}{{$value}}{{end}}{{end}}" octopusbi-agent-backend

What could be the issue?

Answer 1

The issue with the "=" symbol, if you use a double quotation(") mark inside the string enclosed with the double quotation(") marks, you have to add a backslash(\) before every double quotation(") mark excluding the first and last double quotation(") mark.

example:-

"Hello "your_name""  <-- wrong
"Hello \"your_name\""  <-- correct

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Windows

As I mentioned earlier I changed "=" to \"=\" and after that, I got another issue related to some other string value called "VERSION". For that also I had to change "VERSION" to \"VERSION\" and it worked as I expected.

So the final command is,

docker inspect --format="{{range $key, $value := .Config.Env}}{{if eq (index (split $value \"=\") 0) \"VERSION\"}}{{$value}}{{end}}{{end}}" octopusbi-agent-backend

Ubuntu

I ran the same command in Ubuntu with the starting and ending quotations with single quotation(') marks and kept the rest of the double quotation(") marks.

So the final command is,

docker inspect --format='{{range $key, $value := .Config.Env}}{{if eq (index (split $value "=") 0) "VERSION"}}{{$value}}{{end}}{{end}}' octopusbi-agent-backend

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Summary

If you use the docker inspect command with the --format option,

• In Windows:-
  1. You have to start the format string with double quotation(") marks.
  2. If you want to use a double quotation(") mark inside the format string, use \" instead.
• In Ubuntu:-
  1. You have to start the format string with single quotation(') marks.
  2. Feel free to use double quotation(") marks inside the format string.

In the shortest, we have to use the double quotation(") mark inside the format string for both environments if you need to use the quotation mark.