diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..2f2b404
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,200 @@
+#
+#   Configuration parts of GNU Make/GCC build system.
+#   Copyright (C) 2022 by KO Myung-Hun <komh@chollian.net>
+#
+#   This file is part of GNU Make/GCC build system.
+#
+#   This program is free software. It comes without any warranty, to
+#   the extent permitted by applicable law. You can redistribute it
+#   and/or modify it under the terms of the Do What The Fuck You Want
+#   To Public License, Version 2, as published by Sam Hocevar. See
+#   http://www.wtfpl.net/ for more details.
+#
+
+##### Configuration parts that you can modify
+
+# specify sub directories
+SUBDIRS :=
+
+# specify gcc compiler flags for all the programs
+CFLAGS := -Wall -DOS2EMX_PLAIN_CHAR -funsigned-char -O3
+
+# specify g++ compiler flags for all the programs
+CXXFLAGS := -Wall -DOS2EMX_PLAIN_CHAR -funsigned-char -O3
+
+# specify linker flags such as -L option for all the programs
+LDFLAGS :=
+
+# specify dependent libraries such as -l option for all the programs
+LDLIBS :=
+
+ifdef RELEASE
+# specify flags for release mode
+CFLAGS   +=
+CXXFLAGS +=
+LDFLAGS  +=
+else
+# specify flags for debug mode
+CFLAGS   +=
+CXXFLAGS +=
+LDFLAGS  +=
+endif
+
+# specify resource compiler, default is rc if not set
+RC :=
+
+# specify resource compiler flags
+RCFLAGS :=
+
+# set if you want not to compress resources
+NO_COMPRESS_RES :=
+
+# specify BLDLEVEL VENDOR string
+BLDLEVEL_VENDOR := OS/2 Factory
+
+# specify a macro defining version, and a file including that macro
+# to generate BLDLEVEL version string
+BLDLEVEL_VERSION_MACRO :=
+BLDLEVEL_VERSION_FILE :=
+
+# specify BLDLEVEL VERSION string if you want to set VERSION string manually,
+# default is generated with BLDLEVEL_VERSION_MACRO and BLDLEVEL_VERSION_FILE
+# if unset
+BLDLEVEL_VERSION := $(shell date +%y.%m.%d)
+
+# Variables for programs
+#
+# 1. specify a list of programs without an extension with
+#
+#   BIN_PROGRAMS
+#
+# Now, assume
+#
+#   BIN_PROGRAMS := program
+#
+# 2. specify sources for a specific program with
+#
+#   program_SRCS
+#
+# the above is REQUIRED
+#
+# 3. specify various OPTIONAL flags for a specific program with
+#
+#   program_CFLAGS      for gcc compiler flags
+#   program_CXXFLAGS    for g++ compiler flags
+#   program_LDFLAGS     for linker flags
+#   program_LDLIBS      for dependent libraries
+#   program_RCSRC       for rc source
+#   program_RCFLAGS     for rc flags
+#   program_DEF         for .def file
+#   program_EXTRADEPS   for extra dependencies
+#   program_DESC        for a BLDLEVEL description string
+#   program_OUTDIR      for the place where to store .EXE
+
+BIN_PROGRAMS :=
+
+# Variables for libraries
+#
+# 1. specify a list of libraries without an extension with
+#
+#   BIN_LIBRARIES
+#
+# Now, assume
+#
+#   BIN_LIBRARIES := library
+#
+# 2. specify sources for a specific library with
+#
+#   library_SRCS
+#
+# the above is REQUIRED
+#
+# 3. set library type flags for a specific library to a non-empty value
+#
+#   library_LIB         to create a static library
+#   library_DLL         to build a DLL
+#
+# either of the above SHOULD be SET
+#
+# 4. specify various OPTIONAL flags for a specific library with
+#
+#   library_CFLAGS      for gcc compiler flags
+#   library_CXXFLAGS    for g++ compiler flags
+#
+# the above is common for LIB and DLL
+#
+#   library_DLLNAME     for customized DLL name without an extension
+#   library_LDFLAGS     for linker flags
+#   library_LDLIBS      for dependent libraries
+#   library_RCSRC       for rc source
+#   library_RCFLAGS     for rc flags
+#   library_DEF         for .def file, if not set all the symbols are exported
+#   library_NO_EXPORT   if set, no symbols are exported in .def file
+#   library_EXTRADEPS   for extra dependencies
+#   library_NO_IMPLIB   if set, implib is not generated.
+#   library_DESC        for a BLDLEVEL description string
+#   library_OUTDIR      for the place where to store .DLL and so on
+#
+# the above is only for DLL
+
+BIN_LIBRARIES := os2compat
+
+os2compat_DIRS := io memory network process thread
+os2compat_SRCS := $(foreach d,$(os2compat_DIRS),$(wildcard $(d)/*.c))
+os2compat_LIB  := 1
+os2compat_DLL  := 1
+os2compat_DLLNAME := os2comp0
+os2compat_DESC := Supplementary library for missing features in OS/2 kLIBC
+os2compat_OUTDIR := lib
+
+include Makefile.common
+
+# additional stuffs
+
+PREFIX := /usr/local
+LIBDIR := $(PREFIX)/lib
+INCLUDEDIR := $(PREFIX)/include
+
+INSTALL := ginstall
+
+.PHONY: install install_libs install_headers
+
+install: all install_libs install_headers
+
+LIB_FILES := $(os2compat_OUTDIR)/$(os2compat_DLLNAME)$(DLL_EXT) \
+             $(os2compat_OUTDIR)/os2compat$(LIB_EXT) \
+             $(os2compat_OUTDIR)/os2compat$(OMF_LIB_EXT) \
+             $(os2compat_OUTDIR)/os2compat_dll$(LIB_EXT) \
+             $(os2compat_OUTDIR)/os2compat_dll$(OMF_LIB_EXT)
+
+install_libs: $(LIB_FILES)
+	$(INSTALL) -d $(DESTDIR)$(LIBDIR)
+	$(INSTALL) $(LIB_FILES) $(DESTDIR)$(LIBDIR)
+
+HEADER_FILES := include/os2compat/dirent.h \
+                include/os2compat/netdb.h \
+                include/os2compat/poll.h \
+                include/os2compat/semaphore.h \
+                include/os2compat/net/if.h \
+                include/os2compat/sys/mman.h \
+                include/os2compat/sys/socket.h \
+                include/os2compat/sys/xpoll.h
+
+PRIV_HEADER_FILES := io/scandir.h \
+                     memory/mmap.h \
+                     network/cmsg.h \
+                     network/getaddrinfo.h \
+                     network/if_nameindex.h \
+                     network/poll.h \
+                     network/shutdown.h \
+                     network/socklen_t.h \
+                     network/xpoll.h \
+                     thread/semaphore.h
+
+install_headers: $(HEADER_FILES) $(PRIV_HEADER_FILES )
+	for h in $(subst include/,,$(HEADER_FILES)); do \
+	  $(INSTALL) -D include/$$h $(DESTDIR)$(INCLUDEDIR)/$$h; \
+	done
+	for h in $(PRIV_HEADER_FILES); do \
+	  $(INSTALL) -D $$h $(DESTDIR)$(INCLUDEDIR)/os2compat/priv/$$h; \
+	done
diff --git a/Makefile.common b/Makefile.common
new file mode 100644
index 0000000..3c966c1
--- /dev/null
+++ b/Makefile.common
@@ -0,0 +1,299 @@
+#
+#   Common parts of GNU Make/GCC build system
+#   Copyright (C) 2022 by KO Myung-Hun <komh@chollian.net>
+#
+#   This file is part of GNU Make/GCC build system.
+#
+#   This program is free software. It comes without any warranty, to
+#   the extent permitted by applicable law. You can redistribute it
+#   and/or modify it under the terms of the Do What The Fuck You Want
+#   To Public License, Version 2, as published by Sam Hocevar. See
+#   http://www.wtfpl.net/ for more details.
+#
+
+##### Common parts that you don't have to modify
+
+OBJ_EXT     := .o
+LIB_EXT     := .a
+OMF_LIB_EXT := .lib
+EXE_EXT     := .exe
+DLL_EXT     := .dll
+
+.SUFFIXES : .def .exe .dll .a .lib .o .obj .res .c .cpp .h .rc .d $(OBJ_EXT) $(LIB_EXT) $(OMF_LIB_EXT) $(EXE_EXT) $(DLL_EXT)
+
+# set compiler and linker
+CC  := gcc
+CXX := g++
+LD  := g++
+
+# always build with -Zomf
+LDFLAGS += -Zomf
+
+ifneq ($(filter wlink WLINK,$(EMXOMFLD_TYPE)),)
+LDFLAGS += -Zlinker "DISABLE 1121"
+endif
+
+ifdef RELEASE
+# remove symbols
+LDFLAGS  += -s
+# pack the executable and DLLs
+LXLITE   := lxlite /B- /L- /CS
+else
+# enable symbolic debugging
+CFLAGS   += -g
+CXXFLAGS += -g
+LDFLAGS  += -g
+# ignore packing
+LXLITE   := echo ignore packing
+endif
+
+# set archiver
+AR := ar
+
+# default resource compiler is rc
+ifeq ($(strip $(RC)),)
+RC := rc
+endif
+
+# set mkdir -p
+MKDIR_P := mkdir -p
+
+# BLDLEVEL string
+BLDLEVEL_DATE := $(shell LANG=C date +"\" %F %T %^Z  \"")
+BLDLEVEL_HOST = $(shell echo $(HOSTNAME) | cut -b -11)
+
+ifeq ($(strip $(BLDLEVEL_VERSION)),)
+ifneq ($(strip $(BLDLEVEL_VERSION_FILE)),)
+BLDLEVEL_VERSION := $(shell sed -n -e "s/^[ \t]*\#[ \t]*define[ \t]\+$(BLDLEVEL_VERSION_MACRO)[ \t]\+\"\(.*\)\"/\1/p" $(BLDLEVEL_VERSION_FILE))
+endif
+endif
+
+BLDLEVEL := @\#$(BLDLEVEL_VENDOR):$(BLDLEVEL_VERSION)\#@\#\#1\#\#$(BLDLEVEL_DATE)$(BLDLEVEL_HOST)::::::@@
+
+# default verbose is quiet, that is V=0
+QUIET_  = @
+QUIET_0 = @
+
+QUIET = $(QUIET_$(V))
+
+# template to build the executable
+define program_template
+$(1)_DEPS := $(foreach s,$($(1)_SRCS),$(s:$(suffix $(s))=.d))
+$$($(1)_DEPS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_DEPS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_OBJS := $$($(1)_DEPS:.d=$(OBJ_EXT))
+$$($(1)_OBJS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_OBJS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_RES := $$($(1)_RCSRC:.rc=.res)
+
+$(1)_DESC := $(if $($(1)_DESC),$($(1)_DESC),$(1))
+
+$(1)_OUTDIR := $(if $($(1)_OUTDIR),$($(1)_OUTDIR),.)
+
+# create a output directory
+ifneq ($$($(1)_OUTDIR),.)
+$$(shell $(MKDIR_P) $$($(1)_OUTDIR))
+endif
+
+$$($(1)_OUTDIR)/$(1)$(EXE_EXT) : $$($(1)_OBJS) $$($(1)_RES) $$($(1)_DEF) $$($(1)_EXTRADEPS)
+	$(if $(QUIET), @echo [LD] $$@)
+	$(QUIET)$(LD) $(LDFLAGS) $$($(1)_LDFLAGS) -o $$@ $$($(1)_OBJS) $$($(1)_DEF) $(LDLIBS) $$($(1)_LDLIBS)
+ifneq ($$($(1)_RES),)
+ifeq ($(strip $(NO_COMPRESS_RES)),)
+	$(if $(QUIET), @echo [BIND] $$($(1)_RES) to $$@)
+	$(QUIET)$(RC) $$($(1)_RES) $$@
+endif
+endif
+	$(if $(QUIET), @echo [LXLITE] $$@)
+	$(QUIET)$(LXLITE) $$@
+ifneq ($$($(1)_RES),)
+ifneq ($(strip $(NO_COMPRESS_RES)),)
+	$(if $(QUIET), @echo [BIND] $$($(1)_RES) to $$@)
+	$(QUIET)$(RC) $$($(1)_RES) $$@
+endif
+endif
+	$(if $(QUIET), @echo [BLDLEVEL] $$@)
+	$(QUIET)echo $(BLDLEVEL)$$($(1)_DESC) >> $$@
+
+$(1) : $$($(1)_OUTDIR)/$(1)$(EXE_EXT)
+endef
+
+# template to create a static library
+define lib_template
+$(1)_DEPS := $(foreach s,$($(1)_SRCS),$(s:$(suffix $(s))=.d))
+$$($(1)_DEPS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_DEPS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_OBJS := $$($(1)_DEPS:.d=$(OBJ_EXT))
+$$($(1)_OBJS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_OBJS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_OUTDIR := $(if $($(1)_OUTDIR),$($(1)_OUTDIR),.)
+
+# create a output directory
+ifneq ($$($(1)_OUTDIR),.)
+$$(shell $(MKDIR_P) $$($(1)_OUTDIR))
+endif
+
+$$($(1)_OUTDIR)/$(1)$(LIB_EXT) : $$($(1)_OBJS) $$($(1)_EXTRADEPS)
+	$(if $(QUIET), @echo [AR] $$@)
+	$(QUIET)$(AR) cr$(if $(QUIET),,v) $$@ $$($(1)_OBJS)
+
+$$($(1)_OUTDIR)/$(1)$(OMF_LIB_EXT) : $$($(1)_OUTDIR)/$(1)$(LIB_EXT)
+	$(if $(QUIET), @echo [EMXOMF] $$@)
+	$(QUIET)emxomf -o $$@ $$($(1)_OUTDIR)/$(1)$(LIB_EXT)
+
+$(1) : $$($(1)_OUTDIR)/$(1)$(LIB_EXT) $$($(1)_OUTDIR)/$(1)$(OMF_LIB_EXT)
+endef
+
+# template to build DLL
+define dll_template
+$(1)_DEPS := $(foreach s,$($(1)_SRCS),$(s:$(suffix $(s))=.d))
+$$($(1)_DEPS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_DEPS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_OBJS := $$($(1)_DEPS:.d=$(OBJ_EXT))
+$$($(1)_OBJS) : CFLAGS += $($(1)_CFLAGS)
+$$($(1)_OBJS) : CXXFLAGS += $($(1)_CXXFLAGS)
+
+$(1)_RES := $($(1)_RCSRC:.rc=.res)
+
+$(1)_OUTDIR := $(if $($(1)_OUTDIR),$($(1)_OUTDIR),.)
+
+$(1)_DEF := $(if $($(1)_DEF),$($(1)_DEF),$($(1)_OUTDIR)/$(1)_auto.def)
+
+$(1)_DLL_TARGET := $(if $($(1)_DLLNAME),$($(1)_DLLNAME),$(1))$(DLL_EXT)
+
+$(1)_DLL_LIBNAME := $$(notdir $$(basename $$($(1)_DLL_TARGET)))
+
+$(1)_DESC := $(if $($(1)_DESC),$($(1)_DESC),$(1))
+
+# create a output directory
+ifneq ($$($(1)_OUTDIR),.)
+$$(shell $(MKDIR_P) $$($(1)_OUTDIR))
+endif
+
+ifneq ($$(wildcard $(1)_auto.def),)
+ifneq ($$(shell sed -n -e "1s/^LIBRARY[ \t]\+\([^ \t]\+\).*$$$$/\1/p" $$($(1)_DEF)),$$($(1)_DLL_LIBNAME))
+$$(shell touch $$($(1)_OUTDIR)/$(1)_auto.libname)
+endif
+endif
+
+$$($(1)_OUTDIR)/$(1)_auto.libname :
+	$(if $(QUIET), @echo [TOUCH] $$@)
+	$(QUIET)touch $$@
+
+$$($(1)_OUTDIR)/$(1)_auto.def : $$($(1)_OBJS) $$($(1)_OUTDIR)/$(1)_auto.libname
+	$(if $(QUIET), @echo [GEN] $$@)
+	$(QUIET)echo LIBRARY $$($(1)_DLL_LIBNAME) INITINSTANCE TERMINSTANCE > $$@
+	$(QUIET)echo DATA MULTIPLE NONSHARED >> $$@
+ifeq ($(strip $$($(1)_NO_EXPORT)),)
+	$(QUIET)echo EXPORTS >> $$@
+	$(QUIET)emxexp $$($(1)_OBJS) | sed /_DLL_InitTerm/d >> $$@
+endif
+
+$$($(1)_OUTDIR)/$$($(1)_DLL_TARGET) : $$($(1)_OBJS) $$($(1)_RES) $$($(1)_DEF) $$($(1)_EXTRADEPS)
+	$(if $(QUIET), @echo [LD] $$@)
+	$(QUIET)$(LD) -Zdll $(LDFLAGS) $$($(1)_LDFLAGS) -o $$@ $$($(1)_OBJS) $$($(1)_DEF) $(LDLIBS) $$($(1)_LDLIBS)
+ifneq ($$($(1)_RES),)
+ifeq ($(strip $(NO_COMPRESS_RES)),)
+	$(if $(QUIET), @echo [BIND] $$($(1)_RES) to $$@)
+	$(QUIET)$(RC) $$($(1)_RES) $$@
+endif
+endif
+	$(if $(QUIET), @echo [LXLITE] $$@)
+	$(QUIET)$(LXLITE) $$@
+ifneq ($$($(1)_RES),)
+ifneq ($(strip $(NO_COMPRESS_RES)),)
+	$(if $(QUIET), @echo [BIND] $$($(1)_RES) to $$@)
+	$(QUIET)$(RC) $$($(1)_RES) $$@
+endif
+endif
+	$(if $(QUIET), @echo [BLDLEVEL] $$@)
+	$(QUIET)echo $(BLDLEVEL)$$($(1)_DESC) >> $$@
+
+$$($(1)_OUTDIR)/$(1)_dll$(LIB_EXT) : $$($(1)_OUTDIR)/$$($(1)_DLL_TARGET)
+ifeq ($$($(1)_NO_IMPLIB),)
+	$(if $(QUIET), @echo [IMPLIB] $$@)
+	$(QUIET)emximp -o $$@ $$($(1)_OUTDIR)/$$($(1)_DLL_TARGET)
+endif
+
+$$($(1)_OUTDIR)/$(1)_dll$(OMF_LIB_EXT) : $$($(1)_OUTDIR)/$$($(1)_DLL_TARGET)
+ifeq ($$($(1)_NO_IMPLIB),)
+	$(if $(QUIET), @echo [IMPLIB] $$@)
+	$(QUIET)emximp -o $$@ $$($(1)_OUTDIR)/$$($(1)_DLL_TARGET)
+endif
+
+$(1) : $$($(1)_OUTDIR)/$(1)_dll$(LIB_EXT) $$($(1)_OUTDIR)/$(1)_dll$(OMF_LIB_EXT)
+endef
+
+%.d : %.c
+	$(if $(QUIET), @echo [DEP] $@)
+	$(QUIET)$(CC) $(CFLAGS) -MM -MP -MT "$(@:.d=$(OBJ_EXT)) $@" -MF $@ $<
+
+%.d : %.cpp
+	$(if $(QUIET), @echo [DEP] $@)
+	$(QUIET)$(CXX) $(CXXFLAGS) -MM -MP -MT "$(@:.d=$(OBJ_EXT)) $@" -MF $@ $<
+
+%.o : %.c
+	$(if $(QUIET), @echo [CC] $@)
+	$(QUIET)$(CC) $(CFLAGS) -c -o $@ $<
+
+%.obj : %.c
+	$(if $(QUIET), @echo [CC] $@)
+	$(QUIET)$(CC) -Zomf $(CFLAGS) -c -o $@ $<
+
+%.o : %.cpp
+	$(if $(QUIET), @echo [CXX] $@)
+	$(QUIET)$(CXX) $(CXXFLAGS) -c -o $@ $<
+
+%.obj : %.cpp
+	$(if $(QUIET), @echo [CXX] $@)
+	$(QUIET)$(CXX) -Zomf $(CXXFLAGS) -c -o $@ $<
+
+%.res : %.rc
+	$(if $(QUIET), @echo [RC] $@)
+	$(QUIET)$(RC) $(RCFLAGS) -r $< $@
+
+.PHONY : all $(BIN_PROGRAMS) $(BIN_LIBRARIES) clean $(SUBDIRS)
+
+all : $(SUBDIRS) $(BIN_LIBRARIES) $(BIN_PROGRAMS)
+
+# check if both library_LIB and library_DLL is not set
+$(foreach lib,$(BIN_LIBRARIES),$(if $(strip $($(lib)_LIB)$($(lib)_DLL)),,$(error Either of $(lib)_LIB or $(lib)_DLL SHOULD be SET)))
+
+LIB_ENABLED = $(foreach lib,$(1),$(if $($(lib)_LIB),$(lib)))
+DLL_ENABLED = $(foreach dll,$(1),$(if $($(dll)_DLL),$(dll)))
+
+$(foreach prog,$(BIN_PROGRAMS),$(eval $(call program_template,$(prog))))
+$(foreach lib,$(call LIB_ENABLED,$(BIN_LIBRARIES)),$(eval $(call lib_template,$(lib))))
+$(foreach dll,$(call DLL_ENABLED,$(BIN_LIBRARIES)),$(eval $(call dll_template,$(dll))))
+
+clean : $(SUBDIRS)
+	rm -f $(foreach prog,$(BIN_PROGRAMS),$($(prog)_DEPS:.d=.bak))
+	rm -f $(foreach prog,$(BIN_PROGRAMS),$($(prog)_DEPS))
+	rm -f $(foreach prog,$(BIN_PROGRAMS),$($(prog)_OBJS))
+	rm -f $(foreach prog,$(BIN_PROGRAMS),$($(prog)_RES))
+	rm -f $(foreach prog,$(BIN_PROGRAMS),$(addsuffix $(EXE_EXT),$($(prog)_OUTDIR)/$(prog)))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_DEPS:.d=.bak))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_DEPS))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_OBJS))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$(addsuffix $(LIB_EXT),$($(lib)_OUTDIR)/$(lib)))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$(addsuffix $(OMF_LIB_EXT),$($(lib)_OUTDIR)/$(lib)))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_RES))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_OUTDIR)/$(lib)_auto.def)
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_OUTDIR)/$(lib)_auto.libname)
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$(addsuffix _dll$(LIB_EXT),$($(lib)_OUTDIR)/$(lib)))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$(addsuffix _dll$(OMF_LIB_EXT),$($(lib)_OUTDIR)/$(lib)))
+	rm -f $(foreach lib,$(BIN_LIBRARIES),$($(lib)_OUTDIR)/$($(lib)_DLL_TARGET))
+	rm -f $(CLEAN-FILES)
+
+$(SUBDIRS) :
+	$(MAKE) -C $@ RELEASE=$(RELEASE) $(MAKECMDGOALS)
+
+ifeq ($(filter %clean, $(MAKECMDGOALS)),)
+-include $(foreach prog,$(BIN_PROGRAMS),$($(prog)_DEPS))
+-include $(foreach lib,$(BIN_LIBRARIES),$($(lib)_DEPS))
+endif
diff --git a/check.cmd b/check.cmd
index c01b44c..fd0b470 100755
--- a/check.cmd
+++ b/check.cmd
@@ -58,6 +58,8 @@ call checkCC 'network/xpoll.h', 'network/xpoll.c network/poll.c', ,
              'xpoll_query( xpset, 0, 0 );' || g.sNl ||,
              'xpoll_wait( xpset, 0, 0, 0 );';
 
+call checkOS2CompatHeader;
+
 say 'Check completed';
 
 exit 0;
@@ -115,3 +117,33 @@ checkCC: procedure expose G.
     say 'Check passed';
 
     return;
+
+checkOS2CompatHeader: procedure expose G.
+    sHeaderFiles = 'include/os2compat/dirent.h',
+                   'include/os2compat/netdb.h',
+                   'include/os2compat/poll.h',
+                   'include/os2compat/semaphore.h',
+                   'include/os2compat/net/if.h',
+                   'include/os2compat/sys/mman.h',
+                   'include/os2compat/sys/socket.h',
+                   'include/os2compat/sys/xpoll.h';
+    sPrivHeaderFiles = 'io/scandir.h',
+                       'memory/mmap.h',
+                       'network/cmsg.h',
+                       'network/getaddrinfo.h',
+                       'network/if_nameindex.h',
+                       'network/poll.h',
+                       'network/shutdown.h',
+                       'network/socklen_t.h',
+                       'network/xpoll.h',
+                       'thread/semaphore.h';
+    sDestDir = 'include/os2compat/priv';
+
+    address cmd 'ginstall -d' sDestDir;
+    address cmd 'cp -p --parent' sPrivHeaderFiles sDestDir;
+
+    call checkCC sHeaderFiles;
+
+    address cmd 'rm -rf' sDestDir;
+
+    return;
diff --git a/include/os2compat/dirent.h b/include/os2compat/dirent.h
new file mode 100644
index 0000000..f6fd3c0
--- /dev/null
+++ b/include/os2compat/dirent.h
@@ -0,0 +1,18 @@
+/*
+ * dirent.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_DIRENT_H
+#define OS2COMPAT_INCLUDE_DIRENT_H
+
+#include "priv/io/scandir.h"
+
+#endif
diff --git a/include/os2compat/net/if.h b/include/os2compat/net/if.h
new file mode 100644
index 0000000..6ce686b
--- /dev/null
+++ b/include/os2compat/net/if.h
@@ -0,0 +1,18 @@
+/*
+ * net/if.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_NET_IF_H
+#define OS2COMPAT_INCLUDE_NET_IF_H
+
+#include "../priv/network/if_nameindex.h"
+
+#endif
diff --git a/include/os2compat/netdb.h b/include/os2compat/netdb.h
new file mode 100644
index 0000000..8df0652
--- /dev/null
+++ b/include/os2compat/netdb.h
@@ -0,0 +1,18 @@
+/*
+ * netdb.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_NETDB_H
+#define OS2COMPAT_INCLUDE_NETDB_H
+
+#include "priv/network/getaddrinfo.h"
+
+#endif
diff --git a/include/os2compat/poll.h b/include/os2compat/poll.h
new file mode 100644
index 0000000..65e0227
--- /dev/null
+++ b/include/os2compat/poll.h
@@ -0,0 +1,18 @@
+/*
+ * poll.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_POLL_H
+#define OS2COMPAT_INCLUDE_POLL_H
+
+#include "priv/network/poll.h"
+
+#endif
diff --git a/include/os2compat/semaphore.h b/include/os2compat/semaphore.h
new file mode 100644
index 0000000..f813ada
--- /dev/null
+++ b/include/os2compat/semaphore.h
@@ -0,0 +1,18 @@
+/*
+ * semaphore.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_SEMAPHORE_H
+#define OS2COMPAT_INCLUDE_SEMAPHORE_H
+
+#include "priv/thread/semaphore.h"
+
+#endif
diff --git a/include/os2compat/sys/mman.h b/include/os2compat/sys/mman.h
new file mode 100644
index 0000000..a622e77
--- /dev/null
+++ b/include/os2compat/sys/mman.h
@@ -0,0 +1,18 @@
+/*
+ * sys/mman.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_SYS_MMAN_H
+#define OS2COMPAT_INCLUDE_SYS_MMAN_H
+
+#include "../priv/memory/mmap.h"
+
+#endif
diff --git a/include/os2compat/sys/socket.h b/include/os2compat/sys/socket.h
new file mode 100644
index 0000000..e0f10c3
--- /dev/null
+++ b/include/os2compat/sys/socket.h
@@ -0,0 +1,20 @@
+/*
+ * sys/socket.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_SYS_SOCKET_H
+#define OS2COMPAT_INCLUDE_SYS_SOCKET_H
+
+#include "../priv/network/cmsg.h"
+#include "../priv/network/shutdown.h"
+#include "../priv/network/socklen_t.h"
+
+#endif
diff --git a/include/os2compat/sys/xpoll.h b/include/os2compat/sys/xpoll.h
new file mode 100644
index 0000000..82d2556
--- /dev/null
+++ b/include/os2compat/sys/xpoll.h
@@ -0,0 +1,18 @@
+/*
+ * xpoll.h for os2compat
+ *
+ * Copyright (C) 2022 KO Myung-Hun <komh@chollian.net>
+ *
+ * This program is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://www.wtfpl.net/ for more details.
+ */
+
+#ifndef OS2COMPAT_INCLUDE_SYS_XPOLL_H
+#define OS2COMPAT_INCLUDE_SYS_XPOLL_H
+
+#include "../priv/network/xpoll.h"
+
+#endif