Thanks to Vince Vielhaber <vev@michvhf.com>

Here is an os2 psql client, with libpq.a library

contrib/os2client/config.h

@@ -0,0 +1,26 @@
+
+#ifndef TCPIPV4
+# define TCPIPV4
+#endif
+
+#ifndef MAXSOCKETS
+#define MAXSOCKETS 2048
+#endif
+
+/*
+ * DEF_PGPORT is the TCP port number on which the Postmaster listens by
+ * default.  This can be overriden by command options, environment variables,
+ * and the postconfig hook. (set by build script)
+ */
+
+#define DEF_PGPORT "5432"
+
+#define HAVE_TERMIOS_H
+#define HAVE_ENDIAN_H
+
+#define SOCKET_SIZE_TYPE size_t
+
+#define  strcasecmp(s1, s2) stricmp(s1, s2)
+
+
+