I know that I can use envsubst command to replace environment variables inside a file and write it to an output file:
envsubst < input.txt > output.txt However, now I only have a variable and it's not a file. But I still need to replace any environment variable inside it.
export original_text="Hello $name, please come here $date" # I want to be able to replace $name and $date, in the RAM and not on disk and files export $name="John" export $date="tomorrow" output=$(envsubst < $original_text) # this is a pseudo-command echo $output # prints => Hello John, please come here tomorrow Is it possible? How can do this?
1 Answer
Yes, you can use a here-string: <<< "$variable"
Your original_text must be single quoted, otherwise the variables will be replaced on creating original_text.
$ original_text='Hello $name, please come here $date' $ export name="John" $ export date="tomorrow" $ envsubst <<< "$original_text" Hello John, please come here tomorrow Of course, you can save it in a variable like you'd always do:
output=$(envsubst <<< "$original_text") You can also pipe to envsubst, e.g.:
$ printf '%s\n' "$var" | envsubst Hello John, please come here tomorrow 
