Question

I am trying to store user input in a variable and clean that variable in order to keep only alphanumerical caract + some others (I mean [a-zA-Z0-9-_]).

I tried using this but it isn’t exhaustive :

SERVICE_NAME=$(echo $SERVICE_NAME | tr A-Z a-z | tr ' ' _ | tr \' _ | tr \" _)

Do you have some help for this?

Answer 1

$ echo 'asd!@QCW@@D' | tr A-Z a-z | sed -e 's/[^a-zA-Z0-9\-]/_/g'
asd__qcw__d

I would use sed for this and use the ^ (not) operator in your set of valid characters and replace everything else with an underscore. The above shows the syntax with the output.

And, as a bonus, if you want to replace a run of invalid characters with one underscore, just add + to your regular expression (and use the -r switch to sed to make it use extended regular expressions:

$ echo 'asd!@QCW@@D' | tr A-Z a-z | sed -r 's/[^a-zA-Z0-9\-]+/_/g'
asd_qcw_d