diff --git a/docs/source/arch_lang/circuit_library.rst b/docs/source/arch_lang/circuit_library.rst
index 2cab83abd..bf32fc113 100644
--- a/docs/source/arch_lang/circuit_library.rst
+++ b/docs/source/arch_lang/circuit_library.rst
@@ -272,7 +272,7 @@ A circuit model may consist of a number of ports. The port list is mandatory in
 
   - ``io="true|false"`` Specify if this port should be treated as an I/O port of an FPGA fabric. When this is enabled, this port of each circuit model instanciated in FPGA will be added as an I/O of an FPGA.
 
-    .. note:: ``io`` is only valid for ``input`` ports
+    .. note:: global ``output`` ports must be ``io`` ports
 
   - ``mode_select="true|false"`` Specify if this port controls the mode switching in a configurable logic block. This is due to that a configurable logic block can operate in different modes, which is controlled by SRAM bits.
 
@@ -296,3 +296,113 @@ A circuit model may consist of a number of ports. The port list is mandatory in
 .. note::  Different types of ``circuit_model`` have different XML syntax, with which users can highly customize their circuit topologies. See refer to examples of :ref:``circuit_model_example`` for more details.
 
 .. note:: Note that we have a list of reserved port names, which indicate the usage of these ports when building FPGA fabrics. Please do not use ``mem_out``, ``mem_inv``, ``bl``, ``wl``, ``blb``, ``wlb``, ``ccff_head`` and ``ccff_tail``.
+
+FPGA I/O Port 
+^^^^^^^^^^^^^
+
+The ``circuit_model`` support not only highly customizable circuit-level modeling but also flexible I/O connection in the FPGA fabric.
+Typically, circuit ports appear in the primitive modules of a FPGA fabric.
+However, it is also very common that some circuit ports should be I/O of a FPGA fabric.
+Using syntax ``is_global`` and ``is_io``, users can freely define how these ports are connected as FPGA I/Os.
+
+In principle, when ``is_global`` is set ``true``, the port will appear as an FPGA I/O.
+The syntax ``is_io`` is applicable when ``is_global`` is ``true``.
+When ``is_io`` is ``true``, the port from different instances will be treated as independent I/Os.
+When ``is_io`` is ``false``, the port from different instances will be treated as the same I/Os, which are short-wired.
+
+To beef up, the following examples will explain how to use ``is_global`` and ``is_io`` to achieve different types of connections to FPGA I/Os.
+
+.. option:: Global short-wired inputs
+
+.. code-block:: xml
+
+  <port type="input" is_global="true" is_io="false"/>
+
+The global inputs are short wired across different instances. 
+These inputs are widely seen in FPGAs, such as clock ports, which are shared between sequential elements. 
+
+:numref:`fig_global_input_ports` shows an example on how the global inputs are wired inside FPGA fabric.
+
+.. _fig_global_input_ports:
+
+.. figure:: ./figures/global_input_ports.png
+   :scale: 100%
+   :alt: classical inverter 1x symbol
+
+   Short-wired global inputs as an FPGA I/O
+
+.. option:: Global short-wired inouts
+
+.. code-block:: xml
+
+  <port type="inout" is_global="true" is_io="false"/>
+
+The global inouts are short wired across different instances. 
+
+:numref:`fig_global_ioput_ports` shows an example on how the global inouts are wired inside FPGA fabric.
+
+.. _fig_global_inout_ports:
+
+.. figure:: ./figures/global_inout_ports.png
+   :scale: 100%
+   :alt: classical inverter 1x symbol
+
+   Short-wired global inouts as an FPGA I/O
+
+.. option:: General-purpose inputs
+
+.. code-block:: xml
+
+  <port type="input" is_global="true" is_io="true"/>
+
+The general-purpose inputs are independent wired from different instances to separated FPGA I/Os.
+For example, power-gating signals can be applied to each tile of a FPGA.
+
+:numref:`fig_gpin_ports` shows an example on how the general-purpose inputs are wired inside FPGA fabric.
+
+.. _fig_gpin_ports:
+
+.. figure:: ./figures/gpin_ports.png
+   :scale: 100%
+   :alt: classical inverter 1x symbol
+
+   General-purpose inputs as separated FPGA I/Os
+
+.. option:: General-purpose I/O
+
+.. code-block:: xml
+
+  <port type="inout" is_global="true" is_io="true"/>
+
+The general-purpose I/O are independent wired from different instances to separated FPGA I/Os.
+In practice, inout of GPIO cell is typically wired like this.
+
+:numref:`fig_gpin_ports` shows an example on how the general-purpose inouts are wired inside FPGA fabric.
+
+.. _fig_gpio_ports:
+
+.. figure:: ./figures/gpio_ports.png
+   :scale: 100%
+   :alt: classical inverter 1x symbol
+
+   General-purpose inouts as separated FPGA I/Os
+
+.. option:: General-purpose outputs
+
+.. code-block:: xml
+
+  <port type="output" is_global="true" is_io="true"/>
+
+The general-purpose outputs are independent wired from different instances to separated FPGA outputs.
+In practice, these outputs are typically spypads to probe internal signals of a FPGA.
+
+:numref:`fig_gpout_ports` shows an example on how the general-purpose outputs are wired inside FPGA fabric.
+
+.. _fig_gpout_ports:
+
+.. figure:: ./figures/gpout_ports.png
+   :scale: 100%
+   :alt: classical inverter 1x symbol
+
+   General-purpose outputs as separated FPGA I/Os
+
diff --git a/docs/source/arch_lang/figures/global_inout_ports.png b/docs/source/arch_lang/figures/global_inout_ports.png
new file mode 100644
index 000000000..9dd7d2b89
Binary files /dev/null and b/docs/source/arch_lang/figures/global_inout_ports.png differ
diff --git a/docs/source/arch_lang/figures/global_input_ports.png b/docs/source/arch_lang/figures/global_input_ports.png
new file mode 100644
index 000000000..4c9025ab3
Binary files /dev/null and b/docs/source/arch_lang/figures/global_input_ports.png differ
diff --git a/docs/source/arch_lang/figures/gpin_ports.png b/docs/source/arch_lang/figures/gpin_ports.png
new file mode 100644
index 000000000..08da0b8c3
Binary files /dev/null and b/docs/source/arch_lang/figures/gpin_ports.png differ
diff --git a/docs/source/arch_lang/figures/gpio_ports.png b/docs/source/arch_lang/figures/gpio_ports.png
new file mode 100644
index 000000000..4b0362c7b
Binary files /dev/null and b/docs/source/arch_lang/figures/gpio_ports.png differ
diff --git a/docs/source/arch_lang/figures/gpout_ports.png b/docs/source/arch_lang/figures/gpout_ports.png
new file mode 100644
index 000000000..e5140bd99
Binary files /dev/null and b/docs/source/arch_lang/figures/gpout_ports.png differ
diff --git a/docs/source/openfpga_shell/launch_openfpga_shell.rst b/docs/source/openfpga_shell/launch_openfpga_shell.rst
index 3ef6e9fb5..8ef7e3858 100644
--- a/docs/source/openfpga_shell/launch_openfpga_shell.rst
+++ b/docs/source/openfpga_shell/launch_openfpga_shell.rst
@@ -11,6 +11,8 @@ To launch OpenFPGA shell, users can choose two modes.
 
   Launch OpenFPGA in interactive mode where users type-in command by command and get runtime results
 
+  .. warning:: Currently OpenFPGA does not support continued lines and comments
+
 .. option::	--file or -f
 
   Launch OpenFPGA in script mode where users write commands in scripts and FPGA will execute them
diff --git a/docs/source/openfpga_shell/openfpga_commands.rst b/docs/source/openfpga_shell/openfpga_commands.rst
index 8f71cdb54..3712cea0d 100644
--- a/docs/source/openfpga_shell/openfpga_commands.rst
+++ b/docs/source/openfpga_shell/openfpga_commands.rst
@@ -194,7 +194,7 @@ FPGA-SDC
 
   - ``--constrain_zero_delay_paths`` Constrain all the zero-delay paths in FPGA fabric
 
-  .. note:: Zero-delay path may cause errors in some PnR tools as it is considered illegal
+    .. note:: Zero-delay path may cause errors in some PnR tools as it is considered illegal
   
   - ``--verbose`` Enable verbose output
 
diff --git a/docs/source/openfpga_shell/openfpga_script.rst b/docs/source/openfpga_shell/openfpga_script.rst
index dde33a044..7c9bd5548 100644
--- a/docs/source/openfpga_shell/openfpga_script.rst
+++ b/docs/source/openfpga_shell/openfpga_script.rst
@@ -4,8 +4,20 @@ OpenFPGA Script Format
 ----------------------
 
 OpenFPGA accepts a simplified tcl-like script format.
-Commented lines are started with `#`.
-Note that comments can be added inline or as a new line.
+
+.. option:: Comments
+   
+   Any content after a ``#`` will be treated as comments.
+   Comments will not be executed.
+
+  .. note:: comments can be added inline or as a new line. See the example below
+
+.. option:: Continued line
+  
+   Lines to be continued should be finished with ``\``.
+   Continued lines will be conjuncted and executed as one line
+ 
+  .. note:: please ensure necessary spaces. Otherwise it may cause command parser fail.
 
 The following is an example.
 
@@ -21,7 +33,8 @@ The following is an example.
   #write_openfpga_arch -f ./arch_echo.xml
   
   # Annotate the OpenFPGA architecture to VPR data base
-  link_openfpga_arch --activity_file ./test_blif/and.act --sort_gsb_chan_node_in_edges #--verbose
+  link_openfpga_arch --activity_file ./test_blif/and.act \
+                     --sort_gsb_chan_node_in_edges #--verbose
   
   # Check and correct any naming conflicts in the BLIF netlist
   check_netlist_naming_conflict --fix --report ./netlist_renaming.xml
@@ -35,7 +48,8 @@ The following is an example.
   # Build the module graph 
   #  - Enabled compression on routing architecture modules
   #  - Enable pin duplication on grid modules 
-  build_fabric --compress_routing --duplicate_grid_pin #--verbose
+  build_fabric --compress_routing \
+               --duplicate_grid_pin #--verbose
   
   # Repack the netlist to physical pbs
   # This must be done before bitstream generator and testbench generation
@@ -44,14 +58,21 @@ The following is an example.
   
   # Build the bitstream 
   #  - Output the fabric-independent bitstream to a file
-  build_architecture_bitstream --verbose --file /var/tmp/xtang/openfpga_test_src/fabric_indepenent_bitstream.xml
+  build_architecture_bitstream --verbose \
+                               --file /var/tmp/xtang/openfpga_test_src/fabric_indepenent_bitstream.xml
   
   # Build fabric-dependent bitstream
   build_fabric_bitstream --verbose
   
   # Write the Verilog netlist for FPGA fabric
   #  - Enable the use of explicit port mapping in Verilog netlist
-  write_fabric_verilog --file /var/tmp/xtang/openfpga_test_src/SRC --explicit_port_mapping --include_timing --include_signal_init --support_icarus_simulator --print_user_defined_template --verbose
+  write_fabric_verilog --file /var/tmp/xtang/openfpga_test_src/SRC \
+                       --explicit_port_mapping \
+                       --include_timing \
+                       --include_signal_init \
+                       --support_icarus_simulator \
+                       --print_user_defined_template \
+                       --verbose
   
   # Write the Verilog testbench for FPGA fabric
   #  - We suggest the use of same output directory as fabric Verilog netlists
@@ -59,7 +80,11 @@ The following is an example.
   #  - Enable top-level testbench which is a full verification including programming circuit and core logic of FPGA
   #  - Enable pre-configured top-level testbench which is a fast verification skipping programming phase
   #  - Simulation ini file is optional and is needed only when you need to interface different HDL simulators using openfpga flow-run scripts
-  write_verilog_testbench --file /var/tmp/xtang/openfpga_test_src/SRC --reference_benchmark_file_path /var/tmp/xtang/and.v --print_top_testbench --print_preconfig_top_testbench --print_simulation_ini /var/tmp/xtang/openfpga_test_src/simulation_deck.ini
+  write_verilog_testbench --file /var/tmp/xtang/openfpga_test_src/SRC \
+                          --reference_benchmark_file_path /var/tmp/xtang/and.v \
+                          --print_top_testbench \
+                          --print_preconfig_top_testbench \
+                          --print_simulation_ini /var/tmp/xtang/openfpga_test_src/simulation_deck.ini
   
   # Write the SDC files for PnR backend
   #  - Turn on every options here 
diff --git a/libopenfpga/libarchopenfpga/src/check_circuit_library.cpp b/libopenfpga/libarchopenfpga/src/check_circuit_library.cpp
index 2e8c1a214..0abc16a0e 100644
--- a/libopenfpga/libarchopenfpga/src/check_circuit_library.cpp
+++ b/libopenfpga/libarchopenfpga/src/check_circuit_library.cpp
@@ -317,6 +317,18 @@ size_t check_circuit_library_ports(const CircuitLibrary& circuit_lib) {
     }
   }
 
+  /* Check global output ports: make sure they are all I/Os */
+  for (const auto& port : circuit_lib.ports()) {
+    if ( (circuit_lib.port_is_global(port)) 
+      && (CIRCUIT_MODEL_PORT_OUTPUT == circuit_lib.port_type(port))
+      && (false == circuit_lib.port_is_io(port)) ) {
+      VTR_LOG_ERROR("Circuit port (type=%s) of model (name=%s) is defined as global output port but not an I/O!\n",
+                    CIRCUIT_MODEL_PORT_TYPE_STRING[size_t(circuit_lib.port_type(port))],
+                    circuit_lib.model_name(port).c_str());
+      num_err++;
+    }
+  }
+
   /* Check set/reset/config_enable ports: make sure they are all global ports */
   for (const auto& port : circuit_lib.ports()) {
     if ( ( (circuit_lib.port_is_set(port)) 
diff --git a/libopenfpga/libarchopenfpga/src/read_xml_circuit_library.cpp b/libopenfpga/libarchopenfpga/src/read_xml_circuit_library.cpp
index cd8ffd1c5..ba6e6af7f 100644
--- a/libopenfpga/libarchopenfpga/src/read_xml_circuit_library.cpp
+++ b/libopenfpga/libarchopenfpga/src/read_xml_circuit_library.cpp
@@ -489,9 +489,7 @@ void read_xml_circuit_port(pugi::xml_node& xml_port,
   /* Identify if the port is for io, this is only applicable to INPUT ports.
    * By default, it will NOT be a mode selection port
    */
-  if (CIRCUIT_MODEL_PORT_INPUT == circuit_lib.port_type(port)) {
-    circuit_lib.set_port_is_io(port, get_attribute(xml_port, "io", loc_data, pugiutil::ReqOpt::OPTIONAL).as_bool(false));
-  } 
+  circuit_lib.set_port_is_io(port, get_attribute(xml_port, "is_io", loc_data, pugiutil::ReqOpt::OPTIONAL).as_bool(false));
 
   /* Identify if the port is for mode selection, this is only applicable to SRAM ports.
    * By default, it will NOT be a mode selection port
diff --git a/libopenfpga/libopenfpgashell/src/command_exit_codes.h b/libopenfpga/libopenfpgashell/src/command_exit_codes.h
new file mode 100644
index 000000000..f1490e533
--- /dev/null
+++ b/libopenfpga/libopenfpgashell/src/command_exit_codes.h
@@ -0,0 +1,27 @@
+#ifndef COMMAND_EXIT_CODES_H
+#define COMMAND_EXIT_CODES_H
+
+/* Begin namespace openfpga */
+namespace openfpga {
+
+/*********************************************************************
+ * Exit codes to signal success/failure status of command execution
+ * Depend on the exit code, OpenFPGA shell will decide to continue or abort
+ ********************************************************************/
+
+/* Never been executed */
+constexpr int CMD_EXEC_NONE = -1;
+
+/* Everything OK */
+constexpr int CMD_EXEC_SUCCESS = 0;
+
+/* Fatal error occurred, we have to abort and do not execute the rest of commands */
+constexpr int CMD_EXEC_FATAL_ERROR = 1;
+
+/* See minor errors but it will not impact the downsteam. We can continue to execute the rest of commands */
+constexpr int CMD_EXEC_MINOR_ERROR = 2;
+
+
+} /* End namespace openfpga */
+
+#endif
diff --git a/libopenfpga/libopenfpgashell/src/shell.h b/libopenfpga/libopenfpgashell/src/shell.h
index 427580010..1a49b313c 100644
--- a/libopenfpga/libopenfpgashell/src/shell.h
+++ b/libopenfpga/libopenfpgashell/src/shell.h
@@ -10,6 +10,7 @@
 #include "vtr_range.h"
 #include "command.h"
 #include "command_context.h"
+#include "command_exit_codes.h"
 #include "shell_fwd.h"
 
 /* Begin namespace openfpga */
@@ -88,25 +89,49 @@ class Shell {
     ShellCommandId add_command(const Command& cmd, const char* descr);
     void set_command_class(const ShellCommandId& cmd_id, const ShellCommandClassId& cmd_class_id);
     /* Link the execute function to a command
-     * We support here three types of functions to be executed in the shell
-     * 1. Standard function, including the data exchange <T> and commands
-     * 2. Short function, including only the data exchange <T>
-     * 3. Built-in function, including only the shell envoriment variables
-     * 4. Marco function, which directly call a macro function without command parsing
+     * We support here different types of functions to be executed in the shell
      * Users just need to specify the function object and its type will be automatically inferred
+     *
+     * Note that all the function should return exit codes complying to the shell_exit_code.h
+     * execept the internal functions
+     */
+
+    /* Standard function, including the data exchange <T> and commands 
+     * This function requires the data exchange <T> to be constant
+     * This is designed for outputting functions requiring external data than the <T>
      */
     void set_command_const_execute_function(const ShellCommandId& cmd_id,
-                                      std::function<void(const T&, const Command&, const CommandContext&)> exec_func);
+                                      std::function<int(const T&, const Command&, const CommandContext&)> exec_func);
+
+    /* Standard function, including the data exchange <T> and commands 
+     * This function allows modification to the data exchange <T>
+     * This is designed for implementing functions requiring external data than the <T>
+     */
     void set_command_execute_function(const ShellCommandId& cmd_id,
-                                      std::function<void(T&, const Command&, const CommandContext&)> exec_func);
+                                      std::function<int(T&, const Command&, const CommandContext&)> exec_func);
+
+    /* Short function, including only the data exchange <T> 
+     * This function requires the data exchange <T> to be constant
+     * This is designed for outputting functions without external data than the <T>
+     */
     void set_command_const_execute_function(const ShellCommandId& cmd_id,
-                                            std::function<void(const T&)> exec_func);
+                                            std::function<int(const T&)> exec_func);
+
+    /* Short function, including only the data exchange <T> 
+     * This function allows modification to the data exchange <T>
+     * This is designed for internal implementing functions without external data than the <T>
+     */
     void set_command_execute_function(const ShellCommandId& cmd_id,
-                                      std::function<void(T&)> exec_func);
+                                      std::function<int(T&)> exec_func);
+
+    /* Built-in function, including only the shell envoriment variables */
     void set_command_execute_function(const ShellCommandId& cmd_id,
                                       std::function<void()> exec_func);
+
+    /* Marco function, which directly call a macro function without command parsing */
     void set_command_execute_function(const ShellCommandId& cmd_id,
                                       std::function<int(int, char**)> exec_func);
+
     void set_command_dependency(const ShellCommandId& cmd_id,
                                 const std::vector<ShellCommandId>& cmd_dependency);
     ShellCommandClassId add_command_class(const char* name);
@@ -126,7 +151,7 @@ class Shell {
     /* Execute a command, the command line is the user's input to launch a command
      * The common_context is the data structure to exchange data between commands
      */
-    void execute_command(const char* cmd_line, T& common_context);
+    int execute_command(const char* cmd_line, T& common_context);
   private: /* Internal data */ 
     /* Name of the shell, this will appear in the interactive mode */
     std::string name_;
@@ -162,10 +187,10 @@ class Shell {
      * 3. Built-in function, including only the shell envoriment variables
      * 4. Marco function, which directly call a macro function without command parsing
      */
-    vtr::vector<ShellCommandId, std::function<void(const T&, const Command&, const CommandContext&)>> command_const_execute_functions_;  
-    vtr::vector<ShellCommandId, std::function<void(T&, const Command&, const CommandContext&)>> command_standard_execute_functions_;  
-    vtr::vector<ShellCommandId, std::function<void(const T&)>> command_short_const_execute_functions_; 
-    vtr::vector<ShellCommandId, std::function<void(T&)>> command_short_execute_functions_; 
+    vtr::vector<ShellCommandId, std::function<int(const T&, const Command&, const CommandContext&)>> command_const_execute_functions_;  
+    vtr::vector<ShellCommandId, std::function<int(T&, const Command&, const CommandContext&)>> command_standard_execute_functions_;  
+    vtr::vector<ShellCommandId, std::function<int(const T&)>> command_short_const_execute_functions_; 
+    vtr::vector<ShellCommandId, std::function<int(T&)>> command_short_execute_functions_; 
     vtr::vector<ShellCommandId, std::function<void()>> command_builtin_execute_functions_;  
     vtr::vector<ShellCommandId, std::function<int(int, char**)>> command_macro_execute_functions_;  
 
@@ -175,7 +200,7 @@ class Shell {
     vtr::vector<ShellCommandId, e_exec_func_type> command_execute_function_types_;  
 
     /* A flag to indicate if the command has been executed */  
-    vtr::vector<ShellCommandId, bool> command_status_;  
+    vtr::vector<ShellCommandId, int> command_status_;  
 
     /* Dependency graph for different commands,
      * This helps the shell interface to check if a command need other commands to be run before its execution  
diff --git a/libopenfpga/libopenfpgashell/src/shell.tpp b/libopenfpga/libopenfpgashell/src/shell.tpp
index 5fe043f8e..69ec89ab9 100644
--- a/libopenfpga/libopenfpgashell/src/shell.tpp
+++ b/libopenfpga/libopenfpgashell/src/shell.tpp
@@ -131,7 +131,7 @@ ShellCommandId Shell<T>::add_command(const Command& cmd, const char* descr) {
   command_short_execute_functions_.emplace_back();
   command_builtin_execute_functions_.emplace_back();
   command_macro_execute_functions_.emplace_back();
-  command_status_.push_back(false); /* By default, the command should be marked as never executed */
+  command_status_.push_back(CMD_EXEC_NONE); /* By default, the command should be marked as fatal error as it has been never executed */
   command_dependencies_.emplace_back();
 
   /* Register the name in the name2id map */
@@ -155,7 +155,7 @@ void Shell<T>::set_command_class(const ShellCommandId& cmd_id, const ShellComman
 
 template<class T>
 void Shell<T>::set_command_const_execute_function(const ShellCommandId& cmd_id, 
-                                                  std::function<void(const T&, const Command&, const CommandContext&)> exec_func) {
+                                                  std::function<int(const T&, const Command&, const CommandContext&)> exec_func) {
   VTR_ASSERT(true == valid_command_id(cmd_id));
   command_execute_function_types_[cmd_id] = CONST_STANDARD;
   command_const_execute_functions_[cmd_id] = exec_func;
@@ -163,7 +163,7 @@ void Shell<T>::set_command_const_execute_function(const ShellCommandId& cmd_id,
 
 template<class T>
 void Shell<T>::set_command_execute_function(const ShellCommandId& cmd_id, 
-                                            std::function<void(T&, const Command&, const CommandContext&)> exec_func) {
+                                            std::function<int(T&, const Command&, const CommandContext&)> exec_func) {
   VTR_ASSERT(true == valid_command_id(cmd_id));
   command_execute_function_types_[cmd_id] = STANDARD;
   command_standard_execute_functions_[cmd_id] = exec_func;
@@ -171,7 +171,7 @@ void Shell<T>::set_command_execute_function(const ShellCommandId& cmd_id,
 
 template<class T>
 void Shell<T>::set_command_const_execute_function(const ShellCommandId& cmd_id, 
-                                                  std::function<void(const T&)> exec_func) {
+                                                  std::function<int(const T&)> exec_func) {
   VTR_ASSERT(true == valid_command_id(cmd_id));
   command_execute_function_types_[cmd_id] = CONST_SHORT;
   command_short_const_execute_functions_[cmd_id] = exec_func;
@@ -179,7 +179,7 @@ void Shell<T>::set_command_const_execute_function(const ShellCommandId& cmd_id,
 
 template<class T>
 void Shell<T>::set_command_execute_function(const ShellCommandId& cmd_id, 
-                                            std::function<void(T&)> exec_func) {
+                                            std::function<int(T&)> exec_func) {
   VTR_ASSERT(true == valid_command_id(cmd_id));
   command_execute_function_types_[cmd_id] = SHORT;
   command_short_execute_functions_[cmd_id] = exec_func;
@@ -341,9 +341,15 @@ void Shell<T>::run_script_mode(const char* script_file_name, T& context) {
     /* Process the command only when the full command line in ended */
     if (!cmd_line.empty()) {
       VTR_LOG("\nCommand line to execute: %s\n", cmd_line.c_str());
-      execute_command(cmd_line.c_str(), context);
+      int status = execute_command(cmd_line.c_str(), context);
       /* Empty the line ready to start a new line */
       cmd_line.clear();
+
+      /* Check the execution status of the command, if fatal error happened, we should abort immediately */
+      if (CMD_EXEC_FATAL_ERROR == status) {
+        VTR_LOG("Fatal error occurred!\nAbort and enter interactive mode\n");
+        break;
+      }
     }
   }
   fp.close();
@@ -376,16 +382,49 @@ void Shell<T>::print_commands() const {
 
 template <class T>
 void Shell<T>::exit() const {
+  /* Check all the command status, if we see fatal errors or minor errors, we drop an error code */
+  int exit_code = 0;
+  for (const int& status : command_status_) {
+    if ( (status == CMD_EXEC_FATAL_ERROR)
+      || (status == CMD_EXEC_MINOR_ERROR) ) {
+      exit_code = 1;
+      break;
+    }
+  } 
+
+  /* Show error message if we detect any errors */
+  int num_err = 0;
+  if (0 != exit_code) {
+    VTR_LOG("\n");
+    for (const ShellCommandId& cmd : commands()) {
+      if (command_status_[cmd] == CMD_EXEC_FATAL_ERROR) {
+        VTR_LOG_ERROR("Command '%s' execution has fatal errors\n",
+                      commands_[cmd].name().c_str());
+        num_err++;
+      }
+        
+      if (command_status_[cmd] == CMD_EXEC_MINOR_ERROR) {
+        VTR_LOG_ERROR("Command '%s' execution has minor errors\n",
+                      commands_[cmd].name().c_str());
+        num_err++;
+      }
+    }
+  }
+
+  VTR_LOG("\nFinish execution with %d errors\n",
+            num_err);
+
   VTR_LOG("\nThank you for using %s!\n",
           name().c_str());
-  std::exit(0);
+
+  std::exit(exit_code);
 }
 
 /************************************************************************
  * Private executors
  ***********************************************************************/
 template <class T>
-void Shell<T>::execute_command(const char* cmd_line,
+int Shell<T>::execute_command(const char* cmd_line,
                                T& common_context) {
   /* Tokenize the line */
   openfpga::StringToken tokenizer(cmd_line);  
@@ -396,17 +435,18 @@ void Shell<T>::execute_command(const char* cmd_line,
   if (ShellCommandId::INVALID() == cmd_id) {
     VTR_LOG("Try to call a command '%s' which is not defined!\n",
             tokens[0].c_str());
-    return;
+    return CMD_EXEC_FATAL_ERROR;
   }
 
   /* Check the dependency graph to see if all the prequistics have been met */
   for (const ShellCommandId& dep_cmd : command_dependencies_[cmd_id]) {
-    if (false == command_status_[dep_cmd]) {
+    if ( (CMD_EXEC_NONE == command_status_[dep_cmd])
+      || (CMD_EXEC_FATAL_ERROR == command_status_[dep_cmd]) ) {
       VTR_LOG("Command '%s' is required to be executed before command '%s'!\n",
               commands_[dep_cmd].name().c_str(), commands_[cmd_id].name().c_str());
       /* Echo the command help desk */
       print_command_options(commands_[cmd_id]);
-      return;
+      return CMD_EXEC_FATAL_ERROR;
     } 
   }
 
@@ -421,25 +461,22 @@ void Shell<T>::execute_command(const char* cmd_line,
       argv[itok] = (char*)malloc((tokens[itok].length() + 1) * sizeof(char));
       strcpy(argv[itok], tokens[itok].c_str());
     }
-    /* Execute the marco function */
-    command_macro_execute_functions_[cmd_id](tokens.size(), argv);
+    /* Execute the marco function and record the execution status */
+    command_status_[cmd_id] = command_macro_execute_functions_[cmd_id](tokens.size(), argv);
     /* Free the argv */
     for (size_t itok = 0; itok < tokens.size(); ++itok) {
       free(argv[itok]);
     }
     free(argv);
 
-    /* Change the status of the command */
-    command_status_[cmd_id] = true;
-
     /* Finish for macro command, return */
-    return;
+    return command_status_[cmd_id];
   }
  
   if (false == parse_command(tokens, commands_[cmd_id], command_contexts_[cmd_id])) {
     /* Echo the command */
     print_command_options(commands_[cmd_id]);
-    return;
+    return CMD_EXEC_FATAL_ERROR;
   }
  
   /* Parse succeed. Let user to confirm selected options */ 
@@ -448,31 +485,38 @@ void Shell<T>::execute_command(const char* cmd_line,
   /* Execute the command depending on the type of function ! */ 
   switch (command_execute_function_types_[cmd_id]) {
   case CONST_STANDARD:
-    command_const_execute_functions_[cmd_id](common_context, commands_[cmd_id], command_contexts_[cmd_id]);
+    command_status_[cmd_id] = command_const_execute_functions_[cmd_id](common_context, commands_[cmd_id], command_contexts_[cmd_id]);
     break;
   case STANDARD:
-    command_standard_execute_functions_[cmd_id](common_context, commands_[cmd_id], command_contexts_[cmd_id]);
+    command_status_[cmd_id] = command_standard_execute_functions_[cmd_id](common_context, commands_[cmd_id], command_contexts_[cmd_id]);
     break;
   case CONST_SHORT:
-    command_short_const_execute_functions_[cmd_id](common_context);
+    command_status_[cmd_id] = command_short_const_execute_functions_[cmd_id](common_context);
     break;
   case SHORT:
-    command_short_execute_functions_[cmd_id](common_context);
+    command_status_[cmd_id] = command_short_execute_functions_[cmd_id](common_context);
     break;
   case BUILTIN:
     command_builtin_execute_functions_[cmd_id]();
+    /* Built-in execution is always correct */
+    command_status_[cmd_id] = CMD_EXEC_SUCCESS; 
     break;
   /* MACRO should be executed eariler in this function. It should not appear here */
   default:
     /* This is not allowed! Error out */
-    VTR_LOG("Invalid type of execute function for command '%s'!\n",
-            commands_[cmd_id].name().c_str());
+    VTR_LOG_ERROR("Invalid type of execute function for command '%s'!\n",
+                  commands_[cmd_id].name().c_str());
     /* Exit the shell using the exit() function inside this class! */
-    exit();
+    return CMD_EXEC_FATAL_ERROR;
   }
 
-  /* Change the status of the command */
-  command_status_[cmd_id] = true;
+  /* Forbid users to return the status CMD_EXEC_NONE */
+  if (CMD_EXEC_NONE == command_status_[cmd_id]) {
+    VTR_LOG_ERROR("It is illegal to return never-executed status for an executed command!\n");
+    return CMD_EXEC_FATAL_ERROR;
+  }
+
+  return command_status_[cmd_id];
 }
 
 /************************************************************************
diff --git a/libopenfpga/libopenfpgashell/test/test_shell.cpp b/libopenfpga/libopenfpgashell/test/test_shell.cpp
index 649859d85..0edc257dd 100644
--- a/libopenfpga/libopenfpgashell/test/test_shell.cpp
+++ b/libopenfpga/libopenfpgashell/test/test_shell.cpp
@@ -15,16 +15,20 @@ class ShellContext {
 };
 
 static
-void shell_execute_set(ShellContext& context, 
+int shell_execute_set(ShellContext& context, 
                        const Command& cmd, const CommandContext& cmd_context) {
   CommandOptionId opt_id = cmd.option("value");
   /* Get the value of a in the command context */
   context.a = std::atoi(cmd_context.option_value(cmd, opt_id).c_str());
+
+  return CMD_EXEC_SUCCESS; 
 }
 
 static
-void shell_execute_print(ShellContext& context) {
+int shell_execute_print(ShellContext& context) {
   VTR_LOG("a=%d\n", context.a);
+
+  return CMD_EXEC_SUCCESS; 
 }
 
 static
@@ -35,7 +39,7 @@ int shell_execute_print_macro(int argc, char** argv) {
     VTR_LOG("\t[%d]: %s\n", iarg, argv[iarg]);
   }
 
-  return 0;
+  return CMD_EXEC_SUCCESS; 
 }
 
 int main(int argc, char** argv) {
diff --git a/libopenfpga/libopenfpgautil/src/openfpga_digest.cpp b/libopenfpga/libopenfpgautil/src/openfpga_digest.cpp
index 4714700e4..3ae2083df 100644
--- a/libopenfpga/libopenfpgautil/src/openfpga_digest.cpp
+++ b/libopenfpga/libopenfpgautil/src/openfpga_digest.cpp
@@ -3,6 +3,7 @@
  * in OpenFPGA framework
  *******************************************************************/
 #include <sys/stat.h>
+#include <vector>
 #include <algorithm>
 
 /* Headers from vtrutil library */
@@ -117,37 +118,121 @@ std::string find_path_dir_name(const std::string& file_name) {
 /******************************************************************** 
  * Create a directory with a given path
  ********************************************************************/
-bool create_dir_path(const char* dir_path) {
-   /* Give up if the path is empty */
-   if (nullptr == dir_path) {
-     VTR_LOG_ERROR("dir_path is empty and nothing is created.\n");
-     return false;
-   }
+static 
+bool create_dir_path(const std::string& dir_path,
+                     const bool& verbose) {
+  /* Give up if the path is empty */
+  if (true == dir_path.empty()) {
+    VTR_LOG_ERROR("Directory path is empty and nothing will be created.\n");
+    return false;
+  }
 
-   /* Try to create a directory */
-   int ret = mkdir(dir_path, S_IRWXU|S_IRWXG|S_IROTH|S_IXOTH);
+  /* Try to create a directory */
+  int ret = mkdir(dir_path.c_str(), S_IRWXU|S_IRWXG|S_IROTH|S_IXOTH);
 
-   /* Analyze the return flag and output status */
-   switch (ret) {
-   case 0:
-     VTR_LOG("Succeed to create directory '%s'\n",
-             dir_path);
-     return true;
-   case -1:
-     if (EEXIST == errno) {
-       VTR_LOG_WARN("Directory '%s' already exists. Will overwrite contents\n",
-                     dir_path);
-       return true;
-     }
-     break;
-   default:
-     VTR_LOG_ERROR("Create directory '%s'...Failed!\n",
-                 dir_path);
-     exit(1);
-     return false;
+  /* Analyze the return flag and output status */
+  switch (ret) {
+  case 0:
+    VTR_LOGV(verbose,
+             "Succeed to create directory '%s'\n",
+             dir_path.c_str());
+    return true;
+  case -1:
+    if (EEXIST == errno) {
+      VTR_LOGV_WARN(verbose,
+                    "Directory '%s' already exists. Will overwrite contents\n",
+                    dir_path.c_str());
+      return true;
+    }
+    VTR_LOG_ERROR("Create directory '%s'...Failed!\n",
+                  dir_path.c_str());
+    exit(1);
+    break;
+  default:
+    VTR_LOG_ERROR("Create directory '%s'...Failed!\n",
+                  dir_path.c_str());
+    exit(1);
+    return false;
   }
 
   return false;
 }
 
+/******************************************************************** 
+ * Recursively create a directory with a given path
+ * The create_dir_path() function will only try to create a directory
+ * in the last level. If any parent directory is not created, it will
+ * always fail.
+ * This function will try to create all the parent directory before 
+ * creating the last level. 
+ ********************************************************************/
+static 
+bool rec_create_dir_path(const std::string& dir_path) {
+  /* Give up if the path is empty */
+  if (true == dir_path.empty()) {
+    VTR_LOG_ERROR("Directory path is empty and nothing will be created.\n");
+    return false;
+  }
+
+  /* Try to find the positions of all the slashes
+   * which are the splitter between directories
+   */
+  char back_slash = '/';
+
+#ifdef _WIN32
+/* For windows OS, replace any '/' with '\' */
+  char back_slash = '\\';
+#endif 
+
+  std::vector<size_t> slash_pos; 
+ 
+  /* Keep searching until we reach the end of the string */
+  for (size_t pos = 0; pos < dir_path.size(); ++pos) {
+    /* Skip the pos = 0, we should avoid creating any root directory */
+    if ( (back_slash == dir_path.at(pos))
+      && (0 != pos))  {
+      slash_pos.push_back(pos);
+    }
+  }
+
+  /* Create directory by following the position of back slash
+   * For each back slash, create a sub string from the beginning 
+   * and try to create directory
+   */
+  for (const size_t& pos : slash_pos) {
+    std::string sub_dir = dir_path.substr(0, pos);
+
+    /* Turn on verbose output only for the last position: the leaf directory */
+    if (false == create_dir_path(sub_dir, &pos == &slash_pos.back())) {
+      return false;
+    } 
+  }
+
+  return true;
+}
+
+/******************************************************************** 
+ * Top function to create a directory with a given path
+ * Allow users to select if use the recursive way or not
+ *
+ * Strongly recommend to use the recursive way, as it can maximum
+ * guarantee the success in creation of directories
+ ********************************************************************/
+void create_directory(const std::string& dir_path, const bool& recursive) { 
+  std::string formatted_dir_path = format_dir_path(dir_path);
+  bool status = false;
+
+  if (true == recursive) {
+    status = rec_create_dir_path(formatted_dir_path); 
+  } else {
+    status = create_dir_path(formatted_dir_path, true);
+  }
+
+  if (false == status) {
+    VTR_LOG_ERROR("Fail to create directory '%s'\n",
+                  formatted_dir_path.c_str());
+    exit(1);
+  }
+}
+
 } /* namespace openfpga ends */
diff --git a/libopenfpga/libopenfpgautil/src/openfpga_digest.h b/libopenfpga/libopenfpgautil/src/openfpga_digest.h
index 90af3dc4e..0e1cd5d76 100644
--- a/libopenfpga/libopenfpgautil/src/openfpga_digest.h
+++ b/libopenfpga/libopenfpgautil/src/openfpga_digest.h
@@ -23,7 +23,7 @@ std::string find_path_file_name(const std::string& file_name);
 
 std::string find_path_dir_name(const std::string& file_name);
 
-bool create_dir_path(const char* dir_path);
+void create_directory(const std::string& dir_path, const bool& recursive = true); 
 
 } /* namespace openfpga ends */
 
diff --git a/openfpga/src/annotation/check_netlist_naming_conflict.cpp b/openfpga/src/annotation/check_netlist_naming_conflict.cpp
index 3470c9f0a..a8ab94384 100644
--- a/openfpga/src/annotation/check_netlist_naming_conflict.cpp
+++ b/openfpga/src/annotation/check_netlist_naming_conflict.cpp
@@ -11,6 +11,9 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from archopenfpga library */
 #include "write_xml_utils.h" 
 
@@ -213,8 +216,8 @@ void print_netlist_naming_fix_report(const std::string& fname,
  * in the users' BLIF netlist that violates the syntax of OpenFPGA
  * fabric generator, i.e., Verilog generator and SPICE generator
  *******************************************************************/
-void check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
-                                   const Command& cmd, const CommandContext& cmd_context) {
+int check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
+                                  const Command& cmd, const CommandContext& cmd_context) {
   vtr::ScopedStartFinishTimer timer("Check naming violations of netlist blocks and nets");
 
   /* By default, we replace all the illegal characters with '_' */
@@ -231,7 +234,15 @@ void check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
                   num_conflicts);
     VTR_LOGV(0 == num_conflicts, 
              "Check naming conflicts in the netlist passed.\n");
-    return;
+
+    /* If we see conflicts, report minor error */
+    if (0 < num_conflicts) {
+      return CMD_EXEC_MINOR_ERROR;
+    }
+
+    /* Otherwise, we should see zero conflicts */
+    VTR_ASSERT(0 == num_conflicts);
+    return CMD_EXEC_SUCCESS;
   }
 
   /* If the auto correction is enabled, we apply a fix */
@@ -248,6 +259,9 @@ void check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
               cmd_context.option_value(cmd, opt_report).c_str());
     }
   } 
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/annotation/check_netlist_naming_conflict.h b/openfpga/src/annotation/check_netlist_naming_conflict.h
index 54d86bca4..cad6c3963 100644
--- a/openfpga/src/annotation/check_netlist_naming_conflict.h
+++ b/openfpga/src/annotation/check_netlist_naming_conflict.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
-                                   const Command& cmd, const CommandContext& cmd_context); 
+int check_netlist_naming_conflict(OpenfpgaContext& openfpga_context,
+                                  const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/annotation/write_xml_device_rr_gsb.cpp b/openfpga/src/annotation/write_xml_device_rr_gsb.cpp
index 906c71d70..63c5454a7 100644
--- a/openfpga/src/annotation/write_xml_device_rr_gsb.cpp
+++ b/openfpga/src/annotation/write_xml_device_rr_gsb.cpp
@@ -182,7 +182,7 @@ void write_device_rr_gsb_to_xml(const char* sb_xml_dir,
   std::string xml_dir_name = format_dir_path(std::string(sb_xml_dir));
 
   /* Create directories */
-  create_dir_path(xml_dir_name.c_str());
+  create_directory(xml_dir_name);
 
   vtr::Point<size_t> sb_range = device_rr_gsb.get_gsb_range();
 
diff --git a/openfpga/src/base/openfpga_bitstream.cpp b/openfpga/src/base/openfpga_bitstream.cpp
index e732dee92..7e2a19fc4 100644
--- a/openfpga/src/base/openfpga_bitstream.cpp
+++ b/openfpga/src/base/openfpga_bitstream.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from openfpgautil library */
 #include "openfpga_digest.h"
 
@@ -22,8 +25,8 @@ namespace openfpga {
 /********************************************************************
  * A wrapper function to call the build_device_bitstream() in FPGA bitstream
  *******************************************************************/
-void fpga_bitstream(OpenfpgaContext& openfpga_ctx,
-                    const Command& cmd, const CommandContext& cmd_context) {
+int fpga_bitstream(OpenfpgaContext& openfpga_ctx,
+                   const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_verbose = cmd.option("verbose");
   CommandOptionId opt_file = cmd.option("file");
@@ -36,24 +39,30 @@ void fpga_bitstream(OpenfpgaContext& openfpga_ctx,
     std::string src_dir_path = find_path_dir_name(cmd_context.option_value(cmd, opt_file));
 
     /* Create directories */
-    create_dir_path(src_dir_path.c_str());
+    create_directory(src_dir_path);
 
     write_arch_independent_bitstream_to_xml_file(openfpga_ctx.bitstream_manager(),
                                                  cmd_context.option_value(cmd, opt_file));
   }
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 }
 
 /********************************************************************
  * A wrapper function to call the build_fabric_bitstream() in FPGA bitstream
  *******************************************************************/
-void build_fabric_bitstream(OpenfpgaContext& openfpga_ctx,
-                            const Command& cmd, const CommandContext& cmd_context) {
+int build_fabric_bitstream(OpenfpgaContext& openfpga_ctx,
+                           const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_verbose = cmd.option("verbose");
 
   openfpga_ctx.mutable_fabric_bitstream() = build_fabric_dependent_bitstream(openfpga_ctx.bitstream_manager(),
                                                                              openfpga_ctx.module_graph(),
                                                                              cmd_context.option_enable(cmd, opt_verbose));
+  
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_bitstream.h b/openfpga/src/base/openfpga_bitstream.h
index 9dc2ad471..58f1c7e86 100644
--- a/openfpga/src/base/openfpga_bitstream.h
+++ b/openfpga/src/base/openfpga_bitstream.h
@@ -15,11 +15,11 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void fpga_bitstream(OpenfpgaContext& openfpga_ctx,
-                    const Command& cmd, const CommandContext& cmd_context); 
+int fpga_bitstream(OpenfpgaContext& openfpga_ctx,
+                   const Command& cmd, const CommandContext& cmd_context); 
 
-void build_fabric_bitstream(OpenfpgaContext& openfpga_ctx,
-                            const Command& cmd, const CommandContext& cmd_context);
+int build_fabric_bitstream(OpenfpgaContext& openfpga_ctx,
+                           const Command& cmd, const CommandContext& cmd_context);
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_build_fabric.cpp b/openfpga/src/base/openfpga_build_fabric.cpp
index 4e8b44916..67203216a 100644
--- a/openfpga/src/base/openfpga_build_fabric.cpp
+++ b/openfpga/src/base/openfpga_build_fabric.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 #include "device_rr_gsb.h"
 #include "device_rr_gsb_utils.h"
 #include "build_device_module.h"
@@ -56,8 +59,8 @@ void compress_routing_hierarchy(OpenfpgaContext& openfpga_ctx,
 /********************************************************************
  * Build the module graph for FPGA device
  *******************************************************************/
-void build_fabric(OpenfpgaContext& openfpga_ctx,
-                  const Command& cmd, const CommandContext& cmd_context) { 
+int build_fabric(OpenfpgaContext& openfpga_ctx,
+                 const Command& cmd, const CommandContext& cmd_context) { 
 
   CommandOptionId opt_compress_routing = cmd.option("compress_routing");
   CommandOptionId opt_duplicate_grid_pin = cmd.option("duplicate_grid_pin");
@@ -77,6 +80,9 @@ void build_fabric(OpenfpgaContext& openfpga_ctx,
                                                                   cmd_context.option_enable(cmd, opt_compress_routing),
                                                                   cmd_context.option_enable(cmd, opt_duplicate_grid_pin),
                                                                   cmd_context.option_enable(cmd, opt_verbose));
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_build_fabric.h b/openfpga/src/base/openfpga_build_fabric.h
index 824ed63a1..3b63c7ab2 100644
--- a/openfpga/src/base/openfpga_build_fabric.h
+++ b/openfpga/src/base/openfpga_build_fabric.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void build_fabric(OpenfpgaContext& openfpga_ctx,
-                  const Command& cmd, const CommandContext& cmd_context); 
+int build_fabric(OpenfpgaContext& openfpga_ctx,
+                 const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_link_arch.cpp b/openfpga/src/base/openfpga_link_arch.cpp
index 34c98ee8d..65aef7cf8 100644
--- a/openfpga/src/base/openfpga_link_arch.cpp
+++ b/openfpga/src/base/openfpga_link_arch.cpp
@@ -8,6 +8,9 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from vpr library */
 #include "read_activity.h"
 
@@ -59,8 +62,8 @@ bool is_vpr_rr_graph_supported(const RRGraph& rr_graph) {
  * - physical pb_graph nodes and pb_graph pins
  * - circuit models for global routing architecture
  *******************************************************************/
-void link_arch(OpenfpgaContext& openfpga_ctx,
-               const Command& cmd, const CommandContext& cmd_context) { 
+int link_arch(OpenfpgaContext& openfpga_ctx,
+              const Command& cmd, const CommandContext& cmd_context) { 
 
   vtr::ScopedStartFinishTimer timer("Link OpenFPGA architecture to VPR architecture");
 
@@ -105,7 +108,7 @@ void link_arch(OpenfpgaContext& openfpga_ctx,
    * - DeviceRRGSB 
    */
   if (false == is_vpr_rr_graph_supported(g_vpr_ctx.device().rr_graph)) {
-    return;
+    return CMD_EXEC_FATAL_ERROR;
   }
 
   annotate_device_rr_gsb(g_vpr_ctx.device(),
@@ -147,6 +150,9 @@ void link_arch(OpenfpgaContext& openfpga_ctx,
   annotate_simulation_setting(g_vpr_ctx.atom(),
                               openfpga_ctx.net_activity(),
                               openfpga_ctx.mutable_arch().sim_setting);
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_link_arch.h b/openfpga/src/base/openfpga_link_arch.h
index 742c29541..8eba64386 100644
--- a/openfpga/src/base/openfpga_link_arch.h
+++ b/openfpga/src/base/openfpga_link_arch.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void link_arch(OpenfpgaContext& openfpga_context, 
-               const Command& cmd, const CommandContext& cmd_context); 
+int link_arch(OpenfpgaContext& openfpga_context, 
+              const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_lut_truth_table_fixup.cpp b/openfpga/src/base/openfpga_lut_truth_table_fixup.cpp
index 45ecbca31..396842dcd 100644
--- a/openfpga/src/base/openfpga_lut_truth_table_fixup.cpp
+++ b/openfpga/src/base/openfpga_lut_truth_table_fixup.cpp
@@ -7,6 +7,9 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from vpr library */
 #include "vpr_utils.h"
 
@@ -182,7 +185,6 @@ void update_lut_tt_with_post_packing_results(const AtomContext& atom_ctx,
   }
 }
 
-
 /********************************************************************
  * Top-level function to fix up the lut truth table results after packing is done
  * The problem comes from a mismatch between the packing results and 
@@ -194,8 +196,8 @@ void update_lut_tt_with_post_packing_results(const AtomContext& atom_ctx,
  * This function aims to fix the mess after packing so that the truth table
  * can be synchronized
  *******************************************************************/
-void lut_truth_table_fixup(OpenfpgaContext& openfpga_context,
-                           const Command& cmd, const CommandContext& cmd_context) { 
+int lut_truth_table_fixup(OpenfpgaContext& openfpga_context,
+                          const Command& cmd, const CommandContext& cmd_context) { 
 
   vtr::ScopedStartFinishTimer timer("Fix up LUT truth tables after packing optimization");
 
@@ -206,6 +208,9 @@ void lut_truth_table_fixup(OpenfpgaContext& openfpga_context,
                                           g_vpr_ctx.clustering(),
                                           openfpga_context.mutable_vpr_clustering_annotation(),
                                           cmd_context.option_enable(cmd, opt_verbose));
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_lut_truth_table_fixup.h b/openfpga/src/base/openfpga_lut_truth_table_fixup.h
index f11abc7fb..d685a4b44 100644
--- a/openfpga/src/base/openfpga_lut_truth_table_fixup.h
+++ b/openfpga/src/base/openfpga_lut_truth_table_fixup.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void lut_truth_table_fixup(OpenfpgaContext& openfpga_context, 
-                           const Command& cmd, const CommandContext& cmd_context); 
+int lut_truth_table_fixup(OpenfpgaContext& openfpga_context, 
+                          const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_pb_pin_fixup.cpp b/openfpga/src/base/openfpga_pb_pin_fixup.cpp
index cc91bdebe..2a8686190 100644
--- a/openfpga/src/base/openfpga_pb_pin_fixup.cpp
+++ b/openfpga/src/base/openfpga_pb_pin_fixup.cpp
@@ -7,6 +7,9 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from vpr library */
 #include "vpr_utils.h"
 
@@ -254,8 +257,8 @@ void update_pb_pin_with_post_routing_results(const DeviceContext& device_ctx,
  * This function aims to fix the mess after routing so that the net mapping
  * can be synchronized
  *******************************************************************/
-void pb_pin_fixup(OpenfpgaContext& openfpga_context,
-                  const Command& cmd, const CommandContext& cmd_context) { 
+int pb_pin_fixup(OpenfpgaContext& openfpga_context,
+                 const Command& cmd, const CommandContext& cmd_context) { 
 
   vtr::ScopedStartFinishTimer timer("Fix up pb pin mapping results after routing optimization");
 
@@ -268,6 +271,9 @@ void pb_pin_fixup(OpenfpgaContext& openfpga_context,
                                           openfpga_context.vpr_routing_annotation(),
                                           openfpga_context.mutable_vpr_clustering_annotation(),
                                           cmd_context.option_enable(cmd, opt_verbose));
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_pb_pin_fixup.h b/openfpga/src/base/openfpga_pb_pin_fixup.h
index e924c6067..bab4e9565 100644
--- a/openfpga/src/base/openfpga_pb_pin_fixup.h
+++ b/openfpga/src/base/openfpga_pb_pin_fixup.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void pb_pin_fixup(OpenfpgaContext& openfpga_context, 
-                  const Command& cmd, const CommandContext& cmd_context); 
+int pb_pin_fixup(OpenfpgaContext& openfpga_context, 
+                 const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_read_arch.cpp b/openfpga/src/base/openfpga_read_arch.cpp
index 1a36e85a3..214af1612 100644
--- a/openfpga/src/base/openfpga_read_arch.cpp
+++ b/openfpga/src/base/openfpga_read_arch.cpp
@@ -5,6 +5,9 @@
 /* Headers from vtrutil library */
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from archopenfpga library */
 #include "read_xml_openfpga_arch.h"
 #include "check_circuit_library.h"
@@ -22,8 +25,8 @@ namespace openfpga {
  * The command will accept an option '--file' which is the architecture
  * file provided by users  
  *******************************************************************/
-void read_arch(OpenfpgaContext& openfpga_context,
-               const Command& cmd, const CommandContext& cmd_context) {
+int read_arch(OpenfpgaContext& openfpga_context,
+              const Command& cmd, const CommandContext& cmd_context) {
   /* Check the option '--file' is enabled or not 
    * Actually, it must be enabled as the shell interface will check 
    * before reaching this fuction
@@ -44,6 +47,9 @@ void read_arch(OpenfpgaContext& openfpga_context,
    * 3. Simulation settings (TODO)
    */
   check_circuit_library(openfpga_context.arch().circuit_lib);
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 /********************************************************************
@@ -53,8 +59,8 @@ void read_arch(OpenfpgaContext& openfpga_context,
  * The command will accept an option '--file' which is the architecture
  * file provided by users  
  *******************************************************************/
-void write_arch(const OpenfpgaContext& openfpga_context,
-                const Command& cmd, const CommandContext& cmd_context) {
+int write_arch(const OpenfpgaContext& openfpga_context,
+               const Command& cmd, const CommandContext& cmd_context) {
   /* Check the option '--file' is enabled or not 
    * Actually, it must be enabled as the shell interface will check 
    * before reaching this fuction
@@ -68,6 +74,9 @@ void write_arch(const OpenfpgaContext& openfpga_context,
   VTR_LOG("Writing XML architecture to '%s'...\n",
           arch_file_name.c_str());
   write_xml_openfpga_arch(arch_file_name.c_str(), openfpga_context.arch());
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_read_arch.h b/openfpga/src/base/openfpga_read_arch.h
index dcc04d77a..b664a7b3e 100644
--- a/openfpga/src/base/openfpga_read_arch.h
+++ b/openfpga/src/base/openfpga_read_arch.h
@@ -15,11 +15,11 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void read_arch(OpenfpgaContext& openfpga_context,
-               const Command& cmd, const CommandContext& cmd_context); 
+int read_arch(OpenfpgaContext& openfpga_context,
+              const Command& cmd, const CommandContext& cmd_context); 
 
-void write_arch(const OpenfpgaContext& openfpga_context,
-                const Command& cmd, const CommandContext& cmd_context);
+int write_arch(const OpenfpgaContext& openfpga_context,
+               const Command& cmd, const CommandContext& cmd_context);
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_repack.cpp b/openfpga/src/base/openfpga_repack.cpp
index 91c6b4798..fe0529d04 100644
--- a/openfpga/src/base/openfpga_repack.cpp
+++ b/openfpga/src/base/openfpga_repack.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 #include "build_physical_truth_table.h"
 #include "repack.h"
 #include "openfpga_repack.h"
@@ -18,8 +21,8 @@ namespace openfpga {
 /********************************************************************
  * A wrapper function to call the fabric_verilog function of FPGA-Verilog 
  *******************************************************************/
-void repack(OpenfpgaContext& openfpga_ctx,
-            const Command& cmd, const CommandContext& cmd_context) {
+int repack(OpenfpgaContext& openfpga_ctx,
+           const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_verbose = cmd.option("verbose");
 
@@ -35,6 +38,9 @@ void repack(OpenfpgaContext& openfpga_ctx,
                                   g_vpr_ctx.clustering(),
                                   openfpga_ctx.vpr_device_annotation(),
                                   openfpga_ctx.arch().circuit_lib); 
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_repack.h b/openfpga/src/base/openfpga_repack.h
index 0fce62f78..83e4bce63 100644
--- a/openfpga/src/base/openfpga_repack.h
+++ b/openfpga/src/base/openfpga_repack.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void repack(OpenfpgaContext& openfpga_ctx,
-            const Command& cmd, const CommandContext& cmd_context); 
+int repack(OpenfpgaContext& openfpga_ctx,
+           const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_sdc.cpp b/openfpga/src/base/openfpga_sdc.cpp
index cb2e1bf72..21a3ab8fb 100644
--- a/openfpga/src/base/openfpga_sdc.cpp
+++ b/openfpga/src/base/openfpga_sdc.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 /* Headers from openfpgautil library */
 #include "openfpga_digest.h"
 
@@ -22,8 +25,8 @@ namespace openfpga {
 /********************************************************************
  * A wrapper function to call the PnR SDC generator of FPGA-SDC
  *******************************************************************/
-void write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
-                   const Command& cmd, const CommandContext& cmd_context) {
+int write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
+                  const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_output_dir = cmd.option("file");
   CommandOptionId opt_constrain_global_port = cmd.option("constrain_global_port");
@@ -42,7 +45,7 @@ void write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
   std::string sdc_dir_path = format_dir_path(cmd_context.option_value(cmd, opt_output_dir));
 
   /* Create directories */
-  create_dir_path(sdc_dir_path.c_str());
+  create_directory(sdc_dir_path);
 
   PnrSdcOption options(sdc_dir_path);
 
@@ -80,13 +83,16 @@ void write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
                   global_ports,
                   openfpga_ctx.flow_manager().compress_routing());
   }
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 /********************************************************************
  * A wrapper function to call the analysis SDC generator of FPGA-SDC
  *******************************************************************/
-void write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
-                        const Command& cmd, const CommandContext& cmd_context) {
+int write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
+                       const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_output_dir = cmd.option("file");
 
@@ -96,7 +102,7 @@ void write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
   std::string sdc_dir_path = format_dir_path(cmd_context.option_value(cmd, opt_output_dir));
 
   /* Create directories */
-  create_dir_path(sdc_dir_path.c_str());
+  create_directory(sdc_dir_path);
 
   AnalysisSdcOption options(sdc_dir_path);
   options.set_generate_sdc_analysis(true);
@@ -114,6 +120,9 @@ void write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
                        global_ports,
                        openfpga_ctx.flow_manager().compress_routing());
   }
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 }
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_sdc.h b/openfpga/src/base/openfpga_sdc.h
index 110a8cd72..99a87f899 100644
--- a/openfpga/src/base/openfpga_sdc.h
+++ b/openfpga/src/base/openfpga_sdc.h
@@ -15,11 +15,11 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
-                   const Command& cmd, const CommandContext& cmd_context); 
+int write_pnr_sdc(OpenfpgaContext& openfpga_ctx,
+                  const Command& cmd, const CommandContext& cmd_context); 
 
-void write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
-                        const Command& cmd, const CommandContext& cmd_context);
+int write_analysis_sdc(OpenfpgaContext& openfpga_ctx,
+                       const Command& cmd, const CommandContext& cmd_context);
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_verilog.cpp b/openfpga/src/base/openfpga_verilog.cpp
index 1ce23a1d4..c79b68fc2 100644
--- a/openfpga/src/base/openfpga_verilog.cpp
+++ b/openfpga/src/base/openfpga_verilog.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 #include "verilog_api.h"
 #include "openfpga_verilog.h"
 
@@ -17,8 +20,8 @@ namespace openfpga {
 /********************************************************************
  * A wrapper function to call the fabric Verilog generator of FPGA-Verilog 
  *******************************************************************/
-void write_fabric_verilog(OpenfpgaContext& openfpga_ctx,
-                          const Command& cmd, const CommandContext& cmd_context) {
+int write_fabric_verilog(OpenfpgaContext& openfpga_ctx,
+                         const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_output_dir = cmd.option("file");
   CommandOptionId opt_explicit_port_mapping = cmd.option("explicit_port_mapping");
@@ -48,13 +51,16 @@ void write_fabric_verilog(OpenfpgaContext& openfpga_ctx,
                       openfpga_ctx.vpr_device_annotation(),
                       openfpga_ctx.device_rr_gsb(),
                       options);
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 /********************************************************************
  * A wrapper function to call the Verilog testbench generator of FPGA-Verilog 
  *******************************************************************/
-void write_verilog_testbench(OpenfpgaContext& openfpga_ctx,
-                             const Command& cmd, const CommandContext& cmd_context) {
+int write_verilog_testbench(OpenfpgaContext& openfpga_ctx,
+                            const Command& cmd, const CommandContext& cmd_context) {
 
   CommandOptionId opt_output_dir = cmd.option("file");
   CommandOptionId opt_reference_benchmark = cmd.option("reference_benchmark_file_path");
@@ -87,6 +93,9 @@ void write_verilog_testbench(OpenfpgaContext& openfpga_ctx,
                          openfpga_ctx.arch().sim_setting,
                          openfpga_ctx.arch().config_protocol.type(),
                          options);
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_verilog.h b/openfpga/src/base/openfpga_verilog.h
index faf8cf6b0..096039aab 100644
--- a/openfpga/src/base/openfpga_verilog.h
+++ b/openfpga/src/base/openfpga_verilog.h
@@ -15,11 +15,11 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void write_fabric_verilog(OpenfpgaContext& openfpga_ctx,
-                          const Command& cmd, const CommandContext& cmd_context); 
+int write_fabric_verilog(OpenfpgaContext& openfpga_ctx,
+                         const Command& cmd, const CommandContext& cmd_context); 
 
-void write_verilog_testbench(OpenfpgaContext& openfpga_ctx,
-                             const Command& cmd, const CommandContext& cmd_context); 
+int write_verilog_testbench(OpenfpgaContext& openfpga_ctx,
+                            const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/base/openfpga_write_gsb.cpp b/openfpga/src/base/openfpga_write_gsb.cpp
index 9c367ebfb..cdb833c75 100644
--- a/openfpga/src/base/openfpga_write_gsb.cpp
+++ b/openfpga/src/base/openfpga_write_gsb.cpp
@@ -5,6 +5,9 @@
 #include "vtr_time.h"
 #include "vtr_log.h"
 
+/* Headers from openfpgashell library */
+#include "command_exit_codes.h"
+
 #include "write_xml_device_rr_gsb.h"
 
 #include "openfpga_write_gsb.h"
@@ -19,8 +22,8 @@ namespace openfpga {
  * Write internal structrure of all the General Switch Blocks (GSBs)
  * to an XML file 
  *******************************************************************/
-void write_gsb(const OpenfpgaContext& openfpga_ctx,
-               const Command& cmd, const CommandContext& cmd_context) { 
+int write_gsb(const OpenfpgaContext& openfpga_ctx,
+              const Command& cmd, const CommandContext& cmd_context) { 
 
   /* Check the option '--file' is enabled or not 
    * Actually, it must be enabled as the shell interface will check 
@@ -38,6 +41,9 @@ void write_gsb(const OpenfpgaContext& openfpga_ctx,
                              g_vpr_ctx.device().rr_graph,
                              openfpga_ctx.device_rr_gsb(),
                              cmd_context.option_enable(cmd, opt_verbose));
+
+  /* TODO: should identify the error code from internal function execution */
+  return CMD_EXEC_SUCCESS;
 } 
 
 } /* end namespace openfpga */
diff --git a/openfpga/src/base/openfpga_write_gsb.h b/openfpga/src/base/openfpga_write_gsb.h
index 4f7110717..206e6cd5a 100644
--- a/openfpga/src/base/openfpga_write_gsb.h
+++ b/openfpga/src/base/openfpga_write_gsb.h
@@ -15,8 +15,8 @@
 /* begin namespace openfpga */
 namespace openfpga {
 
-void write_gsb(const OpenfpgaContext& openfpga_ctx,
-               const Command& cmd, const CommandContext& cmd_context); 
+int write_gsb(const OpenfpgaContext& openfpga_ctx,
+              const Command& cmd, const CommandContext& cmd_context); 
 
 } /* end namespace openfpga */
 
diff --git a/openfpga/src/fabric/build_grid_modules.cpp b/openfpga/src/fabric/build_grid_modules.cpp
index 95e435f6f..0b693fcec 100644
--- a/openfpga/src/fabric/build_grid_modules.cpp
+++ b/openfpga/src/fabric/build_grid_modules.cpp
@@ -306,22 +306,17 @@ void build_primitive_block_module(ModuleManager& module_manager,
   /* Find the inout ports required by the primitive node, and add them to the module
    * This is mainly due to the I/O blocks, which have inout ports for the top-level fabric
    */
-  if (CIRCUIT_MODEL_IOPAD == circuit_lib.model_type(primitive_model)) {
-    std::vector<CircuitPortId> primitive_model_inout_ports = circuit_lib.model_ports_by_type(primitive_model, CIRCUIT_MODEL_PORT_INOUT);
-    for (auto port : primitive_model_inout_ports) {
+  for (const auto& port : circuit_lib.model_global_ports(primitive_model, false)) {
+    if ( (CIRCUIT_MODEL_PORT_INOUT == circuit_lib.port_type(port))
+      && (true == circuit_lib.port_is_io(port)) ) {
       add_primitive_module_fpga_global_io_port(module_manager, primitive_module,
                                                logic_module, logic_instance_id,
                                                ModuleManager::MODULE_GPIO_PORT,
                                                circuit_lib,
                                                primitive_model,
                                                port);
-    }
-  }
-
-  /* Find the other i/o ports required by the primitive node, and add them to the module */
-  for (const auto& port : circuit_lib.model_global_ports(primitive_model, false)) {
-    if ( (CIRCUIT_MODEL_PORT_INPUT == circuit_lib.port_type(port))
-      && (true == circuit_lib.port_is_io(port)) ) {
+    } else if ( (CIRCUIT_MODEL_PORT_INPUT == circuit_lib.port_type(port))
+             && (true == circuit_lib.port_is_io(port)) ) {
       add_primitive_module_fpga_global_io_port(module_manager, primitive_module,
                                                logic_module, logic_instance_id,
                                                ModuleManager::MODULE_GPIN_PORT,
diff --git a/openfpga/src/fpga_sdc/analysis_sdc_writer.cpp b/openfpga/src/fpga_sdc/analysis_sdc_writer.cpp
index c188dedd8..584f6e63f 100644
--- a/openfpga/src/fpga_sdc/analysis_sdc_writer.cpp
+++ b/openfpga/src/fpga_sdc/analysis_sdc_writer.cpp
@@ -203,6 +203,12 @@ void print_analysis_sdc_disable_global_ports(std::fstream& fp,
       continue;
     }
 
+    /* Skip any gpio port here! */
+    if ( (CIRCUIT_MODEL_PORT_INOUT == circuit_lib.port_type(global_port)) 
+      && (true == circuit_lib.port_is_io(global_port)) ) {
+      continue;
+    }
+
     ModulePortId module_port = module_manager.find_module_port(top_module, circuit_lib.port_prefix(global_port)); 
     BasicPort port_to_disable = module_manager.module_port(top_module, module_port);
 
diff --git a/openfpga/src/fpga_verilog/verilog_api.cpp b/openfpga/src/fpga_verilog/verilog_api.cpp
index dc332db58..c37b68888 100644
--- a/openfpga/src/fpga_verilog/verilog_api.cpp
+++ b/openfpga/src/fpga_verilog/verilog_api.cpp
@@ -63,19 +63,19 @@ void fpga_fabric_verilog(ModuleManager& module_manager,
   std::string src_dir_path = format_dir_path(options.output_directory());
 
   /* Create directories */
-  create_dir_path(src_dir_path.c_str());
+  create_directory(src_dir_path);
 
   /* Sub directory under SRC directory to contain all the primitive block netlists */
   std::string submodule_dir_path = src_dir_path + std::string(DEFAULT_SUBMODULE_DIR_NAME);
-  create_dir_path(submodule_dir_path.c_str());
+  create_directory(submodule_dir_path);
 
   /* Sub directory under SRC directory to contain all the logic block netlists */
   std::string lb_dir_path = src_dir_path + std::string(DEFAULT_LB_DIR_NAME);
-  create_dir_path(lb_dir_path.c_str());
+  create_directory(lb_dir_path);
 
   /* Sub directory under SRC directory to contain all the routing block netlists */
   std::string rr_dir_path = src_dir_path + std::string(DEFAULT_RR_DIR_NAME);
-  create_dir_path(rr_dir_path.c_str());
+  create_directory(rr_dir_path);
 
   /* Print Verilog files containing preprocessing flags */
   print_verilog_preprocessing_flags_netlist(std::string(src_dir_path),
@@ -153,7 +153,7 @@ void fpga_verilog_testbench(const ModuleManager& module_manager,
   std::string netlist_name = atom_ctx.nlist.netlist_name();
 
   /* Create directories */
-  create_dir_path(src_dir_path.c_str());
+  create_directory(src_dir_path);
 
   /* TODO: check if this works here. This function was in fabric generator */
   print_verilog_simulation_preprocessing_flags(std::string(src_dir_path),
diff --git a/openfpga/src/utils/module_manager_utils.cpp b/openfpga/src/utils/module_manager_utils.cpp
index 64bef2e88..a57e97261 100644
--- a/openfpga/src/utils/module_manager_utils.cpp
+++ b/openfpga/src/utils/module_manager_utils.cpp
@@ -37,8 +37,9 @@ ModuleId add_circuit_model_to_module_manager(ModuleManager& module_manager,
 
   /* Add ports */
   /* Find global ports and add one by one 
-   * Global input ports will be considered as global port in the context of module manager
-   * Global output ports will be considered as spy port in the context of module manager
+   * Non-I/O Global input ports will be considered as global port to be shorted wired in the context of module manager
+   * I/O Global output ports will be considered as general purpose output port in the context of module manager
+   * I/O Global inout ports will be considered as general purpose i/o port in the context of module manager
    */
   for (const auto& port : circuit_lib.model_global_ports(circuit_model, false)) {
     BasicPort port_info(circuit_lib.port_prefix(port), circuit_lib.port_size(port));
@@ -50,9 +51,12 @@ ModuleId add_circuit_model_to_module_manager(ModuleManager& module_manager,
     } else if ( (CIRCUIT_MODEL_PORT_INPUT == circuit_lib.port_type(port))
              && (true == circuit_lib.port_is_io(port)) ) {
       module_manager.add_port(module, port_info, ModuleManager::MODULE_GPIN_PORT);  
-    } else {
-      VTR_ASSERT(CIRCUIT_MODEL_PORT_OUTPUT == circuit_lib.port_type(port));
+    } else if (CIRCUIT_MODEL_PORT_OUTPUT == circuit_lib.port_type(port)) {
+      VTR_ASSERT(true == circuit_lib.port_is_io(port));
       module_manager.add_port(module, port_info, ModuleManager::MODULE_GPOUT_PORT);  
+    } else if ( (CIRCUIT_MODEL_PORT_INOUT == circuit_lib.port_type(port)) 
+             && (true == circuit_lib.port_is_io(port)) ) {
+      module_manager.add_port(module, port_info, ModuleManager::MODULE_GPIO_PORT);  
     }
   }
 
diff --git a/openfpga/test_openfpga_arch/k6_N10_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_N10_40nm_openfpga.xml
index 17eb8b550..de0602e1e 100644
--- a/openfpga/test_openfpga_arch/k6_N10_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_N10_40nm_openfpga.xml
@@ -156,7 +156,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_40nm_openfpga.xml
index c43614ae8..51e250a8a 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_40nm_openfpga.xml
@@ -173,7 +173,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_40nm_openfpga.xml
index cf619cd27..ae08c8250 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_40nm_openfpga.xml
@@ -174,7 +174,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_40nm_openfpga.xml
index 4ddf1dd0b..cb145e06d 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_40nm_openfpga.xml
@@ -174,7 +174,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_aib_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_aib_40nm_openfpga.xml
index f0e84e167..e65851291 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_aib_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_chain_mem16K_aib_40nm_openfpga.xml
@@ -174,7 +174,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
@@ -209,7 +209,7 @@
       <port type="output" prefix="rx_data" size="80"/>
       <port type="clock" prefix="tx_clk" size="1" default_val="0"/>
       <port type="clock" prefix="rx_clk" size="1" default_val="0"/>
-      <port type="inout" prefix="pad" size="80"/>
+      <port type="inout" prefix="pad" size="80" is_global="true" is_io="true"/>
     </circuit_model>
   </circuit_library>
   <configuration_protocol>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_column_chain_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_column_chain_40nm_openfpga.xml
index d70ebcb2d..65117d199 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_column_chain_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_column_chain_40nm_openfpga.xml
@@ -174,7 +174,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_chain_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_chain_40nm_openfpga.xml
index 81a9582dc..779880dea 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_chain_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_chain_40nm_openfpga.xml
@@ -174,7 +174,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_scan_chain_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_scan_chain_40nm_openfpga.xml
index 840a2e3bb..621847439 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_scan_chain_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_adder_register_scan_chain_40nm_openfpga.xml
@@ -179,7 +179,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_spyio_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_spyio_40nm_openfpga.xml
index 547c742c8..159214507 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_spyio_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_spyio_40nm_openfpga.xml
@@ -173,11 +173,11 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true" />
       <!-- A spypad for the direction port of the I/O pad, which can be visible in the fpga_top -->
-      <port type="input" prefix="din" size="1" is_global="true" io="true" default_value="0"/>
-      <port type="output" prefix="dout" size="1" is_global="true"/>
-      <port type="output" prefix="dir" size="1" is_global="true"/>
+      <port type="input" prefix="din" size="1" is_global="true" is_io="true" default_value="0"/>
+      <port type="output" prefix="dout" size="1" is_global="true" is_io="true"/>
+      <port type="output" prefix="dir" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_stdcell_mux_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_stdcell_mux_40nm_openfpga.xml
index d3e3d1f6c..59f493a13 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_stdcell_mux_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_stdcell_mux_40nm_openfpga.xml
@@ -165,7 +165,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>
diff --git a/openfpga/test_openfpga_arch/k6_frac_N10_tree_mux_40nm_openfpga.xml b/openfpga/test_openfpga_arch/k6_frac_N10_tree_mux_40nm_openfpga.xml
index 8052fb2dc..d04318510 100644
--- a/openfpga/test_openfpga_arch/k6_frac_N10_tree_mux_40nm_openfpga.xml
+++ b/openfpga/test_openfpga_arch/k6_frac_N10_tree_mux_40nm_openfpga.xml
@@ -164,7 +164,7 @@
       <design_technology type="cmos"/>
       <input_buffer exist="true" circuit_model_name="INVTX1"/>
       <output_buffer exist="true" circuit_model_name="INVTX1"/>
-      <port type="inout" prefix="pad" size="1"/>
+      <port type="inout" prefix="pad" size="1" is_global="true" is_io="true"/>
       <port type="sram" prefix="en" size="1" mode_select="true" circuit_model_name="sc_dff_compact" default_val="1"/>
       <port type="input" prefix="outpad" size="1"/>
       <port type="output" prefix="inpad" size="1"/>