pg_logpipe

pg_logpipe is a log pipe tool that can be used with PostgreSQL. It reads from the standard input and writes the data to the file specified as argument. When the process gets a USR1 signal, then the file is closed and reopened, so it can be rotated away. You could use it with pg_ctl like this:

pg_ctl -D /data/dir start | pg_logpipe logfile

To build pg_logpipe, unpack the source code distribution in the directory src/bin in a PostgreSQL source tree, change into the resulting pg_logpipe directory, and enter make install there.