You Can’T Use Special Characters In Unix Commands If You Use Single-Quotes

what i learned

You can’t insert variables in Unix commands if you’re using single quotes.

this won’t work

export SECRET="huh"

echo 'you can not see my secret $SECRET'

but this will

export SECRET="huh"

echo "you can see my secret $SECRET"

how i learned

while setting up a GitHub action for the social tech collaborative website that would send a url to a specific slack channel, i would get $TARGET_URL instead of the actual url.

turns out special characters are interpreted as literals with single-quotes.

when you use double-quotes, special characters $, \ and ` remain special 🙄

Single quotes (’ ‘) operate similarly to double quotes, but do not permit referencing variables, since the special meaning of $ is turned off. Within single quotes, every special character except’ gets interpreted literally. Consider single quotes (“full quoting”) to be a stricter method of quoting than double quotes (“partial quoting”).
- tldp.org