Building command strings using variables with various quote levels and spaces

Question

I have a script that runs curl. I want to be able to optionally add a -H parameter, if a string isn\'t empty. What\'s complex is the levels of qu

Answer 1

If you only need to know whether or not the caption is there, you can interpolate it when it needs to be there.

caption="Test Caption"
NOCAPT="yeah, sort of, that would be nice"

if [ "${caption}" != "" ]; then 
    unset NOCAPT
fi

curl ${NOCAPT--H "X-Caption: ${caption}"} -A "$UA" ...

To recap, the syntax ${var-value} produces value if var is unset.