How to convert Android contacts2.db to a Vcard .vcf file?

[Fergus Daly]

To try to do this I have followed the hints at
https://www.youtube.com/watch?v=ZKX6R0-EPC4
and therefore
1. installed sqlite and libsqlite-dev 
2. Downloaded dump-contacts2db.sh from https://github.com/stachre/dump-contacts2db/
3. FAILED to turn this script into an executable using chmod +x
and therefore 
4. failed to achieve the one-line command
    $ dump-contacts2db.sh contacts2.db > contacts.vcf
Can anybody help with item 3 or offer an entirely different / better / easier method to achieve the conversion?
Thank you!