Thanks to Vince Vielhaber <vev@michvhf.com>

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

contrib/os2client/Makefile

+#-------------------------------------------------------------------------
+#
+# Makefile
+#    Makefile for libpq library
+#
+# Copyright (c) 1994, Regents of the University of California
+#
+#
+# IDENTIFICATION
+#    $Header: /cvsroot/pgsql/contrib/os2client/Attic/Makefile,v 1.1 1998/10/31 04:10:52 scrappy Exp $
+#
+#-------------------------------------------------------------------------
+
+SO_MAJOR_VERSION=1
+SO_MINOR_VERSION=1
+
+SRCDIR= ../../src
+
+INTERFACES= $(SRCDIR)/interfaces/libpq
+
+PORTNAME=OS2
+
+CC=gcc
+CFLAGS=-I. -I$(SRCDIR)/include
+CFLAGS+=-DFRONTEND -DTCPIPV4 -DHAVE_CRYPT_H
+
+CP= copy
+
+AR=ar
+
+AROPT=rc
+
+RANLIB= ar s
+
+LDFLAGS= -L.
+
+OBJS= fe-auth.o fe-connect.o fe-exec.o fe-misc.o fe-lobj.o fe-print.o \
+      dllist.o pqsignal.o pqcomprim.o
+
+EXEOBJS= psql.o stringutils.o
+
+all: libpq.a c.h psql
+
+fe-auth.o: $(INTERFACES)/fe-auth.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-auth.c
+
+fe-connect.o: $(INTERFACES)/fe-connect.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-connect.c
+
+fe-exec.o: $(INTERFACES)/fe-exec.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-exec.c
+
+fe-lobj.o: $(INTERFACES)/fe-lobj.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-lobj.c
+
+fe-misc.o: $(INTERFACES)/fe-misc.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-misc.c
+
+fe-print.o: $(INTERFACES)/fe-print.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/fe-print.c
+
+pqsignal.o: $(INTERFACES)/pqsignal.c
+	$(CC) $(CFLAGS) -c $(INTERFACES)/pqsignal.c
+
+dllist.o: $(SRCDIR)/backend/lib/dllist.c
+	$(CC) $(CFLAGS) -c $(SRCDIR)/backend/lib/dllist.c
+
+pqcomprim.o: $(SRCDIR)/backend/libpq/pqcomprim.c
+	$(CC) $(CFLAGS) -c $(SRCDIR)/backend/libpq/pqcomprim.c
+
+libpq.a: $(OBJS)
+	$(AR) $(AROPT) libpq.a $(OBJS) 
+	$(RANLIB) libpq.a
+
+psql: $(EXEOBJS)
+	$(CC) -o psql.exe $(EXEOBJS) $(LDFLAGS) -llibpq -lsocket -lufc
+
+psql.o: $(SRCDIR)/bin/psql/psql.c
+	$(CC) $(CFLAGS) -I$(INTERFACES) -c $(SRCDIR)/bin/psql/psql.c 
+
+stringutils.o: $(SRCDIR)/bin/psql/stringutils.c
+	$(CC) $(CFLAGS) -I$(INTERFACES) -c $(SRCDIR)/bin/psql/stringutils.c
+
+c.h: $(SRCDIR)/include/c.h
+	rm -f c.h
+	$(CP) portname c.h
+	cat $(SRCDIR)/include/c.h >> c.h
+
+clean:
+	rm -f libpq.a $(OBJS) $(EXEOBJS) psql.exe c.h dllist.c pqcomprim.c
+

contrib/os2client/README

+
+19981029  libpq.a and psql.exe Version 6.4 for OS/2 
+---------------------------------------------------
+
+
+Requirements:
+
+emx 0.9c or newer under OS/2
+GNU crypt library for emx+gcc version 2.0.6 (available from 
+  ftp://ftp.leo.org/pub/comp/os/os2/leo/crypt/gnuufc.zip)
+
+
+Also a patch is needed for sys/socket.h around line 291.  The lines
+with the pluses need to be added, the other lines are already there
+and are only for reference:
+
+
+#define MT_IFADDR       13
+
++#ifndef MAXSOCKETS
++#define MAXSOCKETS 2048
++#endif
+
+struct mbstat {
+        u_short         m_mbufs;
+        u_short         m_clusters;
+
+
+Possible problems:
+
+  You will also need to #define TCPIPV4
+
+  Make sure both socket.a and ufc.a are linked in to the executable 
+AFTER libpq.a.
+
+The following include files will be needed in order to use the library.
+You only need to include one (libpq-fe.h) but these need to be present:
+
+postgres_ext.h
+libpq/pqcomm.h
+lib/dllist.h"
+c.h
+
+
+Good luck and enjoy!!
+
+Vince Vielhaber <vev@michvhf.com>
+
+
+

contrib/os2client/config.h

+
+#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)
+
+
+

contrib/os2client/portname

+#undef PORTNAME 
+#define PORTNAME OS2