create database in postgresql with bash command

Question

Im trying to create a database in postgresql using linux.
I connected to postgres with

sudo -u postgres psql postgres 
postgres=# then i tried **CREATE DATABASE demo** or **createdb demo**

but none of them worked when i checked with \l command.
Any help ?

Answer 1

sudo su - postgres to become postgres

then psql -c "create database demo" to create it from shell

Answer 2

first:

    sudo su postgres

and then enter your password then type:

     psql

and type this command:

    CREATE DATABASE dbname;