Dynamic loading of C functions: Badly stuck

Hi,
I raised this problem yesterday aswell. I'm badly stuck at this point.
The problem is as follows:

I have a C function that i want to use in my postgres function.
I adopt the following steps to do that.

--- compile the C file as follows
gcc -shared -o test_func.so test_func.c
test_func.c is the name of the C file

--- the name of the function that i want to use from this c file is called
'command'

--- Postgres function is written as follows:

CREATE FUNCTION command(integer) RETURNS integer
AS 'usr/include/pgsql/server/test_func', 'command'
LANGUAGE C STRICT;

when i try to run this function, always gives me the follwoing error:

ERROR: could not access file "usr/include/pgsql/server/test_func": No such
file or directory

I tried changin the permission of the file to 666 and even tried it with 755
but in vein.

I checked the log file but it just prints the above error and doesn't give
me any more information.

I have no clue why is postgres not reading test_func object file.

Any kind of help would be appreciated

Thanks,
~Jas