How to check if a postgres user exists?

Question

createuser allows creation of a user (ROLE) in PostgreSQL. Is there a simple way to check if that user(name) exists already? Otherwise createuser returns with an er

Answer 1

Following the same idea than to check if a db exists

psql -t -c '\du' | cut -d \| -f 1 | grep -qw 

and you can use it in a script like this:

if psql -t -c '\du' | cut -d \| -f 1 | grep -qw ; then
    # user exists
    # $? is 0
else
    # ruh-roh
    # $? is 1
fi