libpq is the C application programmer's interface to Postgres Pro. libpq is a set of library functions that allow client programs to pass queries to the Postgres Pro backend server and to receive the results of these queries.

libpq is also the underlying engine for several other Postgres Pro application interfaces, including those written for C++, Perl, Python, Tcl and ECPG. So some aspects of libpq's behavior will be important to you if you use one of those packages. In particular, Section 37.15, Section 37.16 and Section 37.19 describe behavior that is visible to the user of any application that uses libpq.

Some short programs are included at the end of this chapter (Section 37.22) to show how to write programs that use libpq.

Client programs that use libpq must include the header file libpq-fe.h and must link with the libpq library.