Postgres dump using password on command line

[Ankur Kaushik <ankurkaushik@xxxxxxxxx>]

I have made script for the postgresql dump but unable to get dump only using command line as it require the password when execute the script.

list of database command require Password after enter

psql -l -t | cut -d'|' -f1 | sed -e 's/ //g' -e '/^$/d'

same for pg_dump 

pg_dump $i|gzip > $backupfile