.psqlrcfiles, such as
.psqlrc-9.2. PostgreSQL 9.2 also added the "include relative" command
\irto psql. Combining these two, you can set up psql initialization to take advantage of any new features you want without breaking the use of old psql releases.
For example, I'd like to set up psql to automatically use
\x auto. But if I just put that into
.psqlrc, older psql releases will complain about an unknown command. (I usually have multiple PostgreSQL versions installed, and I share dotfiles across hosts.) On the other hand, I don't want to have to duplicate the entire
.psqlrc file to add one command, which is where
\ir comes in.
Here is what I use, for example:
\ir .psqlrc \set QUIET yes \set COMP_KEYWORD_CASE preserve-lower \x auto \unset QUIET