pg_read_server_files Allow reading files from any location the database can access on the server with COPY and other file-access functions.
pg_write_server_files Allow writing to files in any location the database can access on the server with COPY and other file-access functions.
pg_execute_server_program Allow executing programs on the database server as the user the database runs as with COPY and other functions which allow executing a server-side program.
PostgreSQL Commands
Connecting to the database
psql -h <hostname or ip address> -p <port number of remote machine> -d <database name which you want to connect> -U <username of the database server>