The GNU Readline library greatly increases the usability of psql , the standard PostgreSQL command-line console client. It adds all of the standard functionality of the GNU Readline library to the psql command line, such as being able to easily modify, edit, and retrieve command-history information with the arrow keys and the ability to search the command history (also known as a reverse-i-search ). If the Readline library is already installed on your system, the configuration process should automatically compile readline support with psql .

OpenSSL is an Open Source implementation of the SSL/TLS protocols. OpenSSL is commonly used with utilities such as OpenSSH and Apache-SSL. PostgreSQL can make use of OpenSSL for encrypted connectivity between the psql client application and the PostgreSQL backend. You may also want to consider OpenSSL if you wish to use Stunnel. More information on OpenSSL is located at https://www.openssl.org . Installing and configuring Stunnel for use with PostgreSQL is discussed in Chapter 8.

Tcl/Tk is a combination programming language and graphical toolkit. Although we don't cover the use of Tcl with PostgreSQL, we do cover the use of PgAccess, which is written in Tcl. If you wish to utilize the PgAccess application you will need to install the Tcl/Tk software. The website for Tcl/Tk is https://tcl.activestate.com .

The JDK is the Java Development Kit. It is required for Java development; hence, it is required by PostgreSQL if you wish to enable JDBC support. Ant is a Java-based build tool (somewhat like gmake ) that is also required for JDBC support. The JDK can be downloaded from https://java.sun.com/j2se/index.html , and Ant can be downloaded from https://jakarta.apache.org/ant/index.html .