Re: [HACKERS] How to refer to resource files from UDFs written in C

On 06/09/2017 08:56 AM, Supun Nakandala wrote:

Hi hackers,

I am trying to extend PostgreSQL by adding UDT and UDF for a custom use
case and I am using C language extensions to do that.

However, I have a requirement of reading a text file from one of the C
functions. The compiled *.so files are placed in the "pg_config
--pkglibdir" directory and tried copying my text files there but it didn't
work. I found that, when these shared libs are loaded they are run from a
different working directory. In this case, what is the best way to refer to
my text files from the C code other than giving the absolute path which can
change from system to system.

All backend processes run with the data directory as the current directory. So you can put the files into the data directory, probably best to have a subdirectory there to avoid confusing them with PostgreSQL's own files. Or you could have a config option, to set an absolute path.

- Heikki