Getting file permissions sorted out is a common source of confusion. SELinux may get in your way and need some adjusting, and plain old Unix file permissions can sometimes bite in weird ways. The simplest way I have found to make files accessible to the postgres user is to make a special directory owned by the postgres user and group, and then make all the files in it owned by postgres. Or use a directory already owned by postgres. For example, on my Debian testing system /etc/postgresql/9.0/ is owned by postgres, so I put my files in there. Use the find command to quickly find which files and directories are owned by postgres. This example searches the whole filesystem except for the /proc pseudo-directory and network shares:

# find / -xdev \( -name proc -prune \) -o -user postgres

Putting data into a PostgreSQL table is fun, and you can export it even more easily with the COPY and \copy commands. Again, COPY requires a terminating semi-colon and an output directory that the postgres user can write to, while \copy has no terminating semi-colon and must output to the logged-in psql user's directory. Here are examples of both:

testdb=# COPY comics TO '/etc/postgresql/9.0/main/freakout.txt';