The \watch meta-command allows psql users to automatically (and continuously) re-execute a query.
This behavior is similar to the watch utility of some Linux and Unix environments.
In the following example, we run a simple query on pg_stat_activity and ask psql to repeat it every 5 seconds. You can exit at any time by pressing Ctrl + C:
gabriele=> SELECT count(*) FROM pg_stat_activity;
count
-------
1
(1 row)
gabriele=> \watch 5
Watch every 5s Tue Aug 27 21:47:24 2013
count
-------
1
(1 row)
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