Question

Can I change/su user in the middle of a script?

if [ "$user" == "" ]; then
  echo "Enter the table name";
  read user
fi

gunzip *
chown postgres *
su postgres 
dropdb $user
psql -c "create database $user with encoding 'unicode';" -U dbname template1
psql -d $user -f *.sql

Answer 1

You can, but bash won’t run the subsequent commands as postgres. Instead, do:

su postgres -c 'dropdb $user'

The -c flag runs a command as the user (see man su).