Problem running script

My requirement is
1) to write a query in a file, read the input from that file, run in
postgresql and write the output(query results) into a file. I'm not able to
use combination of \i and \o
Let' say I have file test.sql and in test.sql I write
select * from abc;
Now I need to read the query from the file and write the output to a file.
I tried
=>\i test.sql \o test
but that is not working. I want to write a script which reads query from
file and write output in a file and I want to do everything in one script
and run it background at a particular time of teh day.
2) How do I run scripts in postgresql? How do I set the shell and execute
the script?

Regards,
Sushma