This is about PostgreSQL, not specifically Aurora (PostgreSQL).
Method 1: Write the password in ‘.pgpass’
Create a ‘.pgpass’ file in the home directory and write the password there.
.pgpass Format
hostname:port:database:user:password
Example) 192.168.1.**:5432:dbname:dbuser:password
Creating .pgpass
vi $HOME/.pgpass
aurorapostdb.xxxxxxxxxx.ap-northeast-1.rds.amazonaws.com:5432:aurorapostdb:master:postgres
chmod 600 $HOME/.pgpass
[ec2-user@donald-dev-ec2-bastin ~]$ psql -h aurorapostdb.xxxxxxx.ap-northeast-1.rds.amazonaws.com -U master -d aurorapostdb
psql (10.4, server 10.7)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
Type "help" for help.
aurorapostdb=>
If you don’t change the permissions, a WARNING will appear.
WARNING: password file “/home/ec2-user/.pgpass” has group or world access; permissions should be u=rw (0600) or less
Method 2: Write in environment variable
export PGPASSWORD=postgres
psql -h aurorapostdb.xxxxxxxxxx.ap-northeast-1.rds.amazonaws.com -U master -d aurorapostdb
[ec2-user@donald-dev-ec2-bastin ~]$ export PGPASSWORD=xxxxxxxx
[ec2-user@donald-dev-ec2-bastin ~]$ psql -h aurorapostdb.xxxxxxx.ap-northeast-1.rds.amazonaws.com -U master -d aurorapostdb
psql (10.4, server 10.7)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
Type "help" for help.
aurorapostdb=>
References
33.14. Environment Variables https://www.postgresql.jp/document/10/html/libpq-envars.html
33.15. Password File https://www.postgresql.jp/document/10/html/libpq-pgpass.html