Data dumps to files - best methods?

Good day all

As I am fairly new to postgresql I am trying to find some more info
regarding options to dump specific data to files.

Let me give you guys some idea on what I mean by this....

Currently there is a java/perl process that runs and creates datadumps
for clients with specific data as per specifications and this creates 4
output files which then are compressed and ftp'd to the client.

The current process takes a very long time to run despite the fact that
it does not need to process a lot of data.

Optimisations have been done on the Database side and the process is
still running very long.

What we are now trying to achieve is to use the Linux scripting and SQL
scripting combination to try and rewrite the process in order to compare the
two processes.

However, even though I can get the sql query,etc... how will I use this
to dump the data into the relevant files?

Any suggestions and assistance would be greatly appreciated.

Regards

Machiel