Check if database exists in PostgreSQL using shell

Question

I was wondering if anyone would be able to tell me about whether it is possible to use shell to check if a PostgreSQL database exists?

I am making a shell script and

Answer 1

I'm combining the other answers to a succinct and POSIX compatible form:

psql -lqtA | grep -q "^$DB_NAME|"

A return of true (0) means it exists.

If you suspect your database name might have a non-standard character such as $, you need a slightly longer approach:

psql -lqtA | cut -d\| -f1 | grep -qxF "$DB_NAME"

The -t and -A options make sure the output is raw and not "tabular" or whitespace-padded output. Columns are separated by the pipe character |, so either the cut or the grep has to recognize this. The first column contains the database name.

EDIT: grep with -x to prevent partial name matches.

Answer 2

• In one line:

PGPASSWORD=mypassword psql -U postgres@hostname -h postgres.hostname.com -tAc 'select 1' -d dbnae || echo 0

This will return 1 if db exists 0 if not

• or more readable:

if [ "$(PGPASSWORD=mypassword psql -U postgres@hostname -h postgres.hostname.com -tAc 'select 1' -d dbnae || echo 0 )" = '1' ]
then
    echo "Database already exists"
else
    echo "Database does not exist"
fi