If you're used to SHOW PROCESSLIST; or mysqladmin processlist in MySQL, you might be searching for this same functionality in postgresql. Here's the quick way to get a process list in postgresql:
Switch to the postgres user:
# su - postgres
Get into the postgres shell:
# psql
Then run a quick query:
select * from pg_stat_activity;
NOTE: To actually see the queries being run, you will need logging enabled (it's disabled by default). I don't know how to turn it on yet, so this post will be left open until I find out!
You should set
stats_command_string = on
in your postgresql.conf