PostgreSQL 9.4 Installation – Fix ‘psql: Command Not Found’ Error on Mac OS X

Locate the psql binary. (In a terminal, run locate psql | grep /bin, and make note of the path. (In my case, it's /opt/local/lib/postgresql90/bin/, as it was installed using MacPorts.)

Then, edit the .bash_profile file in your home folder (e.g. mate -w ~/.bash_profile assuming you've textmate), and add the needed line so it's in your path, e.g.:

export PATH=/opt/local/lib/postgresql90/bin/:$PATH

After having saved the file, read the file (. ~/.bash_profile) or open a new terminal, and type psql.

client_encoding is a libpq connection option that was added circa 2011 and will not be recognized by older versions.

The error:

psql: invalid connection option "client_encoding"

comes from dynamically linking a newer psql with an older libpq, for instance the one that ships with the system.

On Mac OS X, this can be worked around by setting DYLD_LIBRARY_PATH (the equivalent of linux's LD_LIBRARY_PATH) to the path of the newer PostgreSQL installation.

Per comments and update, it's confirmed to work when setting this variable globally in /etc/profile