postgres=# select
postgres-#     get_total_kb(file_system) as "1K-blocks",
postgres-#     (get_total_kb(file_system) - get_avail_kb(file_system)) as "Used",
postgres-#     get_avail_kb(file_system) as "Available",
postgres-#     cast
postgres-#       (
postgres(#         ((get_total_kb(file_system) - get_avail_kb(file_system)) * 100.0) / get_total_kb(file_system) + 0.499999
postgres(# as numeric(3,0)
postgres(#       ) as "Use%",
postgres-#     file_system as "Mounted on"
postgres-#   from file_system()
postgres-#   where get_total_kb(file_system) > 0;
 1K-blocks |   Used   | Available | Use% | Mounted on
-----------+----------+-----------+------+------------
  36699288 | 11810908 |  24888380 |   33 | /
    777680 |       12 |    777668 |    1 | /dev/shm
(2 rows)

postgres=# \q
kgrittn@linux:~> df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1             36699288  11810908  24888380  33% /
tmpfs                   777680        12    777668   1% /dev/shm