String substitution with file contents

Question

I have a file called tags.txt which contains a tag on each line, for example:

workflow
blogging
writing

Using the "Advanced Bash Scripting Guide" I've written a Bash script that takes these lines and makes them into a single-line comma-delimited list.

tagsraw=$(<tags.txt)
tags=${tagsraw//$'\n'/', '}

How can I do this in one line of code?

Whenever I have tried putting the (<tags.txt) in place of tagsraw in the second line, in numerous forms, I get a "bad substitution" error. Is doing this on one line, without an intermediary variable, in Bash even possible?

Answer 1

You can use awk :

tags="$(awk -v OFS=', ' -v RS= '{$1=$1}1' tags.txt)"
echo "$tags"
workflow, blogging, writing