psql --host=localhost --dbname=test
psql  -h localhost -d test
\d
\dt
\ds

psql  -h localhost -d test -E
\o out.txt
show data_directory;
\! cat out.txt
\! ls
\o 
\! rm out.txt
\! ls
\! echo "SELECT 1; " > a.sql
\i a.sql 
\! cat a.sql
\timing
select now();
\set PROMPT1 '%n@%/  '
\timing
\set HISTFILE ~/history-:DBNAME 