diff --git a/README.md b/README.md
index 87fe6e2..bbab8c7 100644
--- a/README.md
+++ b/README.md
@@ -7,12 +7,20 @@
 TODO
 
 ### Build
-
-TODO
+run this command:
+    autoreconf --force --verbose --install
 
 ### Test
+run this command:
+     ./configure CFLAGS='-std=c99 -Werror -Wall -Wextra -Wvla'
+then:
+    make
 
-TODO
+#### asan
+run this command:
+    ./configure CFLAGS='-std=c99 -Werror -Wall -Wextra -Wvla -g -fsanitize=address'
+then:
+    make check
 
 ## Authors
 
diff --git a/configure.ac b/configure.ac
index 4a89a36..f9684ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,9 @@
 # Init the 42sh project
 AC_INIT([42sh], [1.0], [matteo.flebus@epita.fr])
 
+# FLAGS="-std=c99 -pedantic -Werror -Wall -Wextra -Wvla"
+# AC_SUBST([FLAGS])
+
 # Setup Automake
 AM_INIT_AUTOMAKE([subdir-objects] [foreign])
 
@@ -21,10 +24,17 @@ AC_PROG_CC
 
 # List Makefiles in subdirectories
 AC_CONFIG_FILES([
-                    Makefile
                     src/Makefile
                     src/ast/Makefile
                     src/parser/Makefile
                     src/lexer/Makefile
+                    src/io_backend/Makefile
+                    src/execution/Makefile
+                    src/expansion/Makefile
+                    src/utils/Makefile
                 ])
+                    # TODO add tests Makefile here
+                    # tests/Makefile
+                    # tests/unit/Makefile
+                    # tests/unit/utils/Makefile
 AC_OUTPUT
diff --git a/src/Makefile.am b/src/Makefile.am
index 8ecd21f..411f4cb 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,11 +1,10 @@
 # define the subdirectories
 SUBDIRS = \
-		ast \
 		parser \
 		lexer \
 		io_backend \
 		execution \
-		expansin \
+		expansion \
 		utils
 
 bin_PROGRAMS = 42sh
@@ -14,10 +13,7 @@ bin_PROGRAMS = 42sh
 
 42sh_CPPFLAGS = -I%D%
 
-42sh_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 42sh_LDADD =  \
-		ast/libast.a \
 		parser/libparser.a \
 		lexer/liblexer.a \
 		io_backend/libio_backend.a \
@@ -27,20 +23,16 @@ bin_PROGRAMS = 42sh
 
 
 ################################################# Test
-
-bin_PROGRAMS = 42sh_asan
-
-42sh_asan_SOURCES = main.c
-
-42sh_asan_CPPFLAGS = -I%D%
-
-42sh_asan_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla -g -fsanitize=address
-
-42sh_asan_LDADD =  \
-		ast/libast.a \
-		parser/libparser.a \
-		lexer/liblexer.a \
-		io_backend/libio_backend.a \
-		expansion/libexpansion.a \
-		execution/libexecution.a \
-		utils/libutils.a
+#
+#42sh_asan_SOURCES = main.c
+#
+#42sh_asan_CPPFLAGS = -I%D%
+#
+#42sh_asan_LDADD =  \
+#		ast/lib_asan_ast.a \
+#		parser/lib_asan_parser.a \
+#		lexer/lib_asan_lexer.a \
+#		io_backend/lib_asan_io_backend.a \
+#		expansion/lib_asan_expansion.a \
+#		execution/lib_asan_execution.a \
+#		utils/lib_asan_utils.a
diff --git a/src/ast/ast.c b/src/ast/ast.c
deleted file mode 100644
index e69de29..0000000
diff --git a/src/ast/ast.h b/src/ast/ast.h
deleted file mode 100644
index b3be544..0000000
--- a/src/ast/ast.h
+++ /dev/null
@@ -1,39 +0,0 @@
-#ifndef AST_H
-#define AST_H
-
-#include "../utils/lists/lists.h"
-
-enum ast_type
-{
-    AST_END = 0,
-    AST_IF,
-    AST_CMD
-};
-
-struct ast_cmd
-{
-    struct list *cmd;
-};
-
-union ast_node;
-
-struct ast
-{
-    enum ast_type type;
-    union ast_node *data;
-};
-
-struct ast_if
-{
-    struct ast *condition;
-    struct ast *then_clause;
-    struct ast *else_clause;
-};
-
-union ast_node
-{
-    struct ast_if ast_if;
-    struct ast_cmd ast_cmd;
-};
-
-#endif /* ! AST_H */
diff --git a/src/execution/Makefile.am b/src/execution/Makefile.am
index f83e3ba..5a71cbb 100644
--- a/src/execution/Makefile.am
+++ b/src/execution/Makefile.am
@@ -6,6 +6,4 @@ libexecution_a_SOURCES =  \
 
 libexecution_a_CPPFLAGS = -I$(top_srcdir)/src
 
-libexecution_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = libexecution.a
diff --git a/src/expansion/Makefile.am b/src/expansion/Makefile.am
index 5074622..065f225 100644
--- a/src/expansion/Makefile.am
+++ b/src/expansion/Makefile.am
@@ -6,6 +6,4 @@ libexpansion_a_SOURCES =  \
 
 libexpansion_a_CPPFLAGS = -I$(top_srcdir)/src
 
-libexpansion_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = libexpansion.a
diff --git a/src/io_backend/Makefile.am b/src/io_backend/Makefile.am
index 7f056b2..0cfadff 100644
--- a/src/io_backend/Makefile.am
+++ b/src/io_backend/Makefile.am
@@ -6,6 +6,4 @@ libio_backend_a_SOURCES =  \
 
 libio_backend_a_CPPFLAGS = -I$(top_srcdir)/src
 
-libio_backend_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = libio_backend.a
diff --git a/src/lexer/Makefile.am b/src/lexer/Makefile.am
index a113221..dd11411 100644
--- a/src/lexer/Makefile.am
+++ b/src/lexer/Makefile.am
@@ -6,6 +6,4 @@ liblexer_a_SOURCES =  \
 
 liblexer_a_CPPFLAGS = -I$(top_srcdir)/src
 
-liblexer_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = liblexer.a
diff --git a/src/parser/Makefile.am b/src/parser/Makefile.am
index 51c8cb6..dd13901 100644
--- a/src/parser/Makefile.am
+++ b/src/parser/Makefile.am
@@ -6,6 +6,4 @@ libparser_a_SOURCES =  \
 
 libparser_a_CPPFLAGS = -I$(top_srcdir)/src
 
-libparser_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = libparser.a
diff --git a/src/utils/Makefile.am b/src/utils/Makefile.am
index dba2e51..5b72df3 100644
--- a/src/utils/Makefile.am
+++ b/src/utils/Makefile.am
@@ -1,11 +1,8 @@
 lib_LIBRARIES = libutils.a
 
-# libutils_a_SOURCES =  \
-#   utils.c \
-#   utils.h
+libutils_a_SOURCES =  \
+	string_utils.c
 
-# libutils_a_CPPFLAGS = -I$(top_srcdir)/src
+libutils_a_CPPFLAGS = -I$(top_srcdir)/src
 
-# libutils_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
-# noinst_LIBRARIES = libutils.a
+noinst_LIBRARIES = libutils.a
diff --git a/src/ast/Makefile.am b/src/utils/ast/Makefile.am
similarity index 67%
rename from src/ast/Makefile.am
rename to src/utils/ast/Makefile.am
index 9df484e..fa41e3d 100644
--- a/src/ast/Makefile.am
+++ b/src/utils/ast/Makefile.am
@@ -6,6 +6,4 @@ libast_a_SOURCES =  \
 
 libast_a_CPPFLAGS = -I$(top_srcdir)/src
 
-libast_a_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
-
 noinst_LIBRARIES = libast.a
diff --git a/src/utils/ast/ast.c b/src/utils/ast/ast.c
new file mode 100644
index 0000000..40b42d7
--- /dev/null
+++ b/src/utils/ast/ast.c
@@ -0,0 +1,68 @@
+#include "ast.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+bool ast_is_if(struct ast *node)
+{
+    assert(node != NULL);
+    return node->type == AST_IF;
+}
+
+bool ast_is_cmd(struct ast *node)
+{
+    assert(node != NULL);
+    return node->type == AST_CMD;
+}
+
+struct ast_if *ast_get_if(struct ast *node)
+{
+    assert(node != NULL);
+    assert(node->type == AST_IF);
+    return (struct ast_if *)node->data;
+}
+
+struct ast_cmd *ast_get_cmd(struct ast *node)
+{
+    assert(node != NULL);
+    assert(node->type == AST_CMD);
+    return (struct ast_cmd *)node->data;
+}
+
+static struct ast *ast_create(enum ast_type type, void *data)
+{
+    struct ast *node = malloc(sizeof(struct ast));
+    if (!node)
+        return NULL;
+
+    node->type = type;
+    node->data = data;
+
+    return node;
+}
+
+struct ast *ast_create_if(struct ast *condition, struct ast *then_clause,
+                          struct ast *else_clause)
+{
+    struct ast_if *if_data = malloc(sizeof(struct ast_if));
+    if (!if_data)
+        return NULL;
+
+    if_data->condition = condition;
+    if_data->then_clause = then_clause;
+    if_data->else_clause = else_clause;
+
+    return ast_create(AST_IF, if_data);
+}
+
+struct ast *ast_create_cmd(struct list *cmd)
+{
+    struct ast_cmd *cmd_data = malloc(sizeof(struct ast_cmd));
+    if (!cmd_data)
+        return NULL;
+
+    cmd_data->cmd = cmd;
+
+    return ast_create(AST_CMD, cmd_data);
+}
diff --git a/src/utils/ast/ast.h b/src/utils/ast/ast.h
new file mode 100644
index 0000000..3247ba5
--- /dev/null
+++ b/src/utils/ast/ast.h
@@ -0,0 +1,73 @@
+#ifndef AST_H
+#define AST_H
+
+#include <stdbool.h>
+
+#include "../lists/lists.h"
+
+enum ast_type
+{
+    AST_END,
+    AST_IF,
+    AST_CMD
+};
+
+struct ast_cmd
+{
+    struct list *cmd;
+};
+
+struct ast_if
+{
+    struct ast *condition;
+    struct ast *then_clause;
+    struct ast *else_clause;
+};
+
+struct ast
+{
+    enum ast_type type;
+
+    /**
+     * Data associated with this AST node. It can be one of the following:
+     * - NULL (AST_END)
+     * - struct ast_if* (AST_IF)
+     * - struct ast_cmd* (AST_CMD)
+     */
+    void *data;
+};
+
+/**
+ * Checks if the given AST node is an if statement.
+ */
+bool ast_is_if(struct ast *node);
+
+/**
+ * Checks if the given AST node is a command.
+ */
+bool ast_is_cmd(struct ast *node);
+
+/**
+ * Retrieves the if statement data from the given AST node.
+ * Assumes that the node is of type AST_IF.
+ */
+struct ast_if *ast_get_if(struct ast *node);
+
+/**
+ * Retrieves the command data from the given AST node.
+ * Assumes that the node is of type AST_CMD.
+ */
+struct ast_cmd *ast_get_cmd(struct ast *node);
+
+/**
+ * Creates a new AST node representing an if statement.
+ */
+struct ast *ast_create_if(struct ast *condition, struct ast *then_clause,
+                          struct ast *else_clause);
+
+/**
+ * Creates a new AST node representing a command.
+ */
+struct ast *ast_create_cmd(struct list *cmd);
+
+#endif /* ! AST_H */