diff --git a/src/main.c b/src/main.c
index f1d0c00..e548360 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,6 +31,9 @@ static int main_loop(struct lexer_context *ctx, struct args_options *options,
                      struct hash_map *vars)
 {
     int return_code = SUCCESS;
+    // init parser
+    int parser_init();
+
     // Retrieve and build first AST
     struct ast *command_ast = get_ast(ctx);
 
@@ -61,6 +64,7 @@ static int main_loop(struct lexer_context *ctx, struct args_options *options,
         return err_input(&vars);
 
     ast_free(&command_ast);
+    parser_close();
 
     return return_code;
 }
diff --git a/src/parser/Makefile.am b/src/parser/Makefile.am
index 3b7b6f5..642414b 100644
--- a/src/parser/Makefile.am
+++ b/src/parser/Makefile.am
@@ -2,7 +2,9 @@ lib_LIBRARIES = libparser.a
 
 libparser_a_SOURCES =  \
   parser.c \
-  parsing_utils.c
+  grammar.c \
+  grammar_basic.c \
+  grammar_advanced.c
 
 libparser_a_CPPFLAGS = -I$(top_srcdir)/src
 
diff --git a/src/parser/grammar.c b/src/parser/grammar.c
new file mode 100644
index 0000000..02098e0
--- /dev/null
+++ b/src/parser/grammar.c
@@ -0,0 +1,206 @@
+// === Includes
+#include "grammar.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "grammar_basic.h"
+
+// === Static variables
+
+// rule-indexed array containing firsts
+static struct firsts_list *firsts_map = NULL;
+
+// === Static functions
+
+/* @brief Add a token to a rule's firsts (in firsts_map)
+ *
+ * @arg rule the rule to which add a first
+ * @arg token the token to add to the rule's firsts
+ * @return true on success, false on error
+ */
+static bool add_first(enum rule rule, enum token_type token)
+{
+    struct firsts_list *item = &firsts_map[rule];
+    if (item->tokens != NULL)
+    {
+        // Check for duplicates
+        for (size_t i = 0; i < item->list_length; i++)
+        {
+            if (item->tokens[i] == token)
+                return true;
+        }
+
+        // Append
+        item->list_length++;
+        item->tokens = realloc(
+            item->tokens, (item->list_length) * sizeof(enum token_type));
+    }
+    else
+    {
+        // Create entry
+        item->list_length = 1;
+        item->tokens = calloc(1, sizeof(enum token_type));
+    }
+
+    // Check for alloc error
+    if (item->tokens == NULL)
+    {
+        item->list_length = 0;
+        return false;
+    }
+
+    // Fill
+    item->list_length++;
+    item->tokens[item->list_length - 1] = token;
+
+    return true;
+}
+
+/* @brief initializes the firsts_map static variable (does not populate it)
+ * @return true on success, false on error
+ */
+static bool init_firsts_map(void)
+{
+    firsts_map = calloc(NUMBER_OF_RULES, sizeof(struct firsts_list));
+    if (firsts_map == NULL)
+    {
+        puts("Internal error: couldn't create the firsts_map (is your memory "
+             "full ?)");
+        return false;
+    }
+
+    return true;
+}
+
+/* @brief: add all the redirection token_types to the first of [rule].
+ *          this also contains IONUMBER
+ */
+static void add_first_redir(enum rule rule)
+{
+    add_first(rule, TOKEN_IONUMBER);
+    add_first(rule, TOKEN_REDIR_LEFT);
+    add_first(rule, TOKEN_REDIR_RIGHT);
+    add_first(rule, TOKEN_REDIR_LEFT_RIGHT);
+    add_first(rule, TOKEN_REDIR_DOUBLE_RIGHT);
+    add_first(rule, TOKEN_REDIR_LEFT_AMP);
+    add_first(rule, TOKEN_REDIR_RIGHT_PIPE);
+}
+
+// === Functions
+
+bool grammar_init(void)
+{
+    // Initialize the firsts map
+    bool success = init_firsts_map();
+    if (success != true)
+        return false;
+
+    // Populate the firsts map
+    add_first(RULE_INPUT, TOKEN_WORD);
+    add_first(RULE_INPUT, TOKEN_IF);
+    add_first(RULE_INPUT, TOKEN_NEWLINE);
+    add_first(RULE_INPUT, TOKEN_EOF);
+
+    add_first(RULE_LIST, TOKEN_WORD);
+    add_first(RULE_LIST, TOKEN_IF);
+
+    add_first(RULE_AND_OR, TOKEN_WORD);
+    add_first(RULE_AND_OR, TOKEN_IF);
+
+    add_first(RULE_PIPELINE, TOKEN_WORD);
+    add_first(RULE_PIPELINE, TOKEN_IF);
+
+    add_first(RULE_COMMAND, TOKEN_WORD);
+    add_first(RULE_COMMAND, TOKEN_IF);
+
+    add_first(RULE_SIMPLE_COMMAND, TOKEN_WORD);
+
+    add_first(RULE_SHELL_COMMAND, TOKEN_IF);
+
+    add_first(RULE_IF, TOKEN_IF);
+
+    add_first(RULE_COMPOUND_LIST, TOKEN_NEWLINE);
+    add_first(RULE_COMPOUND_LIST, TOKEN_WORD);
+    add_first(RULE_COMPOUND_LIST, TOKEN_IF);
+
+    add_first(RULE_ELSE_CLAUSE, TOKEN_ELSE);
+    add_first(RULE_ELSE_CLAUSE, TOKEN_ELIF);
+
+    add_first(RULE_ELEMENT, TOKEN_WORD);
+    add_first_redir(RULE_ELEMENT);
+
+    add_first_redir(RULE_REDIRECTION);
+
+    add_first_redir(RULE_PREFIX);
+
+    return true;
+}
+
+void grammar_close(void)
+{
+    // Deep free firsts map
+    for (int i = 0; i < NUMBER_OF_RULES; i++)
+    {
+        if (firsts_map[i].tokens != NULL)
+        {
+            free(firsts_map[i].tokens);
+        }
+    }
+    free(firsts_map);
+    firsts_map = NULL;
+}
+
+struct firsts_list *first(enum rule rule)
+{
+    if (firsts_map == NULL || firsts_map[rule].tokens == NULL)
+    {
+        puts("Internal error: attempted to get the firsts of a rule without "
+             "properly initializing the firsts map");
+        return NULL;
+    }
+
+    return &firsts_map[rule];
+}
+
+bool is_first(struct token token, enum rule rule)
+{
+    struct firsts_list *firsts = &firsts_map[rule];
+    for (size_t i = 0; i < firsts->list_length; i++)
+    {
+        if (firsts->tokens[i] == token.type)
+            return true;
+    }
+
+    return false;
+}
+
+struct ast *parse_input(struct lexer_context *ctx)
+{
+    struct token *token = PEEK_TOKEN();
+
+    if (token->type == TOKEN_EOF)
+        return ast_create_list(NULL);
+
+    if (token->type == TOKEN_NEWLINE)
+    {
+        POP_TOKEN();
+        return ast_create_list(NULL);
+    }
+
+    struct ast *ast = parse_list(ctx);
+    if (ast == NULL)
+        return NULL;
+
+    token = PEEK_TOKEN();
+    if (token->type == TOKEN_NEWLINE || token->type == TOKEN_EOF)
+    {
+        if (token->type == TOKEN_NEWLINE)
+            POP_TOKEN();
+        return ast;
+    }
+
+    puts("Syntax error: expected newline or EOF after list");
+    ast_free(&ast);
+    return NULL;
+}
diff --git a/src/parser/grammar.h b/src/parser/grammar.h
new file mode 100644
index 0000000..5721ee7
--- /dev/null
+++ b/src/parser/grammar.h
@@ -0,0 +1,93 @@
+#ifndef GRAMMAR_H
+#define GRAMMAR_H
+
+#include <stdbool.h>
+
+#include "../lexer/lexer.h"
+
+// === Macros
+
+#define PEEK_TOKEN()                                                           \
+    peek_token(ctx);                                                           \
+    if (token == NULL)                                                         \
+    {                                                                          \
+        puts("Internal error: cannot get the following token");                \
+        return NULL;                                                           \
+    }
+
+#define POP_TOKEN()                                                            \
+    pop_token(ctx);                                                            \
+    if (token == NULL)                                                         \
+    {                                                                          \
+        puts("Internal error: cannot get the following token");                \
+        return NULL;                                                           \
+    }
+
+// === Structures
+
+enum rule {
+    RULE_NULL = 0,
+    RULE_INPUT,
+    RULE_LIST,
+    RULE_AND_OR,
+    RULE_PIPELINE,
+    RULE_COMMAND,
+    RULE_SIMPLE_COMMAND,
+    RULE_SHELL_COMMAND,
+    RULE_IF,
+    RULE_COMPOUND_LIST,
+    RULE_ELSE_CLAUSE,
+    RULE_ELEMENT,
+    RULE_REDIRECTION,
+    RULE_PREFIX,
+    NUMBER_OF_RULES
+};
+
+struct firsts_list {
+    enum token_type* tokens; // Heap allocated array
+    size_t list_length;
+};
+
+// === Functions
+
+/*
+ * @brief Initializes the grammar submodule
+ * @return PARSER_INIT_SUCCESS on success PARSER_INIT_ERROR on error
+ * @warning Do not use outside the parser
+ */
+bool grammar_init(void);
+
+/*
+ * @brief Closes the grammar submodule
+ * @warning Do not use outside the parser
+ */
+void grammar_close(void);
+
+/*
+ * @brief get the first accepted tokens of a rule
+ *
+ * @arg r the rule
+ * @return the accepted tokens as a firsts_list struct
+ */
+struct firsts_list *first(enum rule r);
+
+/*
+ * @brief tells is token belong to the firsts of a specific rule
+ *
+ * @arg token
+ * @arg rule
+ * @return true if token belongs to rule's firsts, false otherwise
+ */
+bool is_first(struct token token, enum rule rule);
+
+/* @brief Acts as the entry point of the parser, calls parse_list
+ *
+ * @code input = list '\n'
+ *             | list EOF
+ *             | '\n'
+ *             | EOF
+ *             ;
+ */
+struct ast *parse_input(struct lexer_context *ctx);
+
+#endif /* ! GRAMMAR_H */
diff --git a/src/parser/grammar_advanced.c b/src/parser/grammar_advanced.c
new file mode 100644
index 0000000..aac5742
--- /dev/null
+++ b/src/parser/grammar_advanced.c
@@ -0,0 +1,45 @@
+#include "grammar_advanced.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "grammar_basic.h"
+
+struct ast *parse_redirection(struct lexer_context *ctx)
+{
+    struct token *token = PEEK_TOKEN();
+    int io_number = -1;
+    if (token->type == TOKEN_IONUMBER)
+    {
+        io_number = atoi(token->data);
+        POP_TOKEN();
+        token = PEEK_TOKEN();
+    }
+
+    if (token->type != TOKEN_REDIRECTION)
+    {
+        puts("Syntax error: expected a redirection token but got something "
+             "else");
+        return NULL;
+    }
+    char *redir_op = strdup(token->data);
+    POP_TOKEN();
+
+    token = PEEK_TOKEN();
+    if (token->type != TOKEN_WORD)
+    {
+        puts("Syntax error: expected a word after redirection");
+        free(redir_op);
+        return NULL;
+    }
+    char *target = strdup(token->data);
+    POP_TOKEN();
+
+    return ast_create_redir(io_number, redir_op, target);
+}
+
+struct ast *parse_prefix(struct lexer_context *ctx)
+{
+    return parse_redirection(ctx);
+}
diff --git a/src/parser/grammar_advanced.h b/src/parser/grammar_advanced.h
new file mode 100644
index 0000000..72b5a43
--- /dev/null
+++ b/src/parser/grammar_advanced.h
@@ -0,0 +1,27 @@
+#ifndef GRAMMAR_ADVANCED_H
+#define GRAMMAR_ADVANCED_H
+
+#include "grammar.h"
+
+// === Functions
+
+/*
+ * @brief parses a redirection rule
+ *
+ * @code redirection = [IONUMBER] ( '>' | '<' | '>>' | '>&' | '<&' | '>|' | '<>' ) WORD ;
+ *
+ * @first TOKEN_IONUMBER, TOKEN_REDIRECTION
+ */
+struct ast *parse_redirection(struct lexer_context *ctx);
+
+/*
+ * @brief parses a prefix rule
+ *
+ * @code prefix = redirection ;
+ *
+ * @first first(redirection)
+ */
+struct ast *parse_prefix(struct lexer_context *ctx);
+
+
+#endif /* ! GRAMMAR_ADVANCED_H */
diff --git a/src/parser/parsing_utils.c b/src/parser/grammar_basic.c
similarity index 71%
rename from src/parser/parsing_utils.c
rename to src/parser/grammar_basic.c
index 2daeb3d..a0e0868 100644
--- a/src/parser/parsing_utils.c
+++ b/src/parser/grammar_basic.c
@@ -1,19 +1,15 @@
-#define _POSIX_C_SOURCE 200809L
+#include "grammar_basic.h"
 
-// === Includes
-#include "parsing_utils.h"
-
-#include <stdbool.h>
-#include <stddef.h>
 #include <stdio.h>
 #include <string.h>
 
-#include "../lexer/lexer.h"
-#include "../utils/ast/ast.h"
+#include "../utils/lists/lists.h"
+#include "grammar.h"
+#include "grammar_advanced.h"
 
 // === Static functions
 
-enum ast_and_or_type and_or_tok_to_ast(enum token_type tok_type)
+static enum ast_and_or_type and_or_tok_to_ast(enum token_type tok_type)
 {
     switch (tok_type)
     {
@@ -27,53 +23,8 @@ enum ast_and_or_type and_or_tok_to_ast(enum token_type tok_type)
     }
 }
 
-/* Returns true if c is a command terminator, false otherwise
-static bool isterminator(struct token *token)
-{
-    if (token == NULL)
-        return false;
-
-    switch (token->type)
-    {
-    case TOKEN_NEWLINE:
-    case TOKEN_SEMICOLON:
-    case TOKEN_EOF:
-        return true;
-    default:
-        return false;
-    }
-}
-
- */
-
-/* @brief: returns true if token is an end of list indicator.
- * @warning: not used
- */
-
-/*
-static bool is_end_of_list(struct token *token)
-{
-    if (token == NULL)
-        return false;
-
-    switch (token->type)
-    {
-        case TOKEN_NEWLINE:
-        case TOKEN_EOF:
-            return true;
-        default:
-            return false;
-    }
-}
-*/
-
 // === Functions
 
-struct ast *parse_input(struct lexer_context *ctx)
-{
-    return parse_list(ctx);
-}
-
 struct ast *parse_list(struct lexer_context *ctx)
 {
     struct list *result_list = NULL;
@@ -92,20 +43,20 @@ struct ast *parse_list(struct lexer_context *ctx)
     while (token->type == TOKEN_SEMICOLON)
     {
         token = POP_TOKEN();
-        // if (!isterminator(token)) // Follow(list)
-        // {
-        current_node = parse_and_or(ctx);
-        if (current_node == NULL)
-        {
-            // TODO free list
-            //  There must be a function for that
-            return NULL;
-        }
-        result_list = list_append(result_list, current_node);
-        // }
         token = PEEK_TOKEN();
+        if (is_first(*token, RULE_AND_OR))
+        {
+            current_node = parse_and_or(ctx);
+            if (current_node == NULL)
+            {
+                struct ast *tmp = ast_create_list(result_list);
+                ast_free(&tmp);
+                return NULL;
+            }
+            result_list = list_append(result_list, current_node);
+            token = PEEK_TOKEN();
+        }
     }
-    // result_list = list_append(result_list, current_node);
 
     return ast_create_list(result_list);
 }
@@ -113,33 +64,41 @@ struct ast *parse_list(struct lexer_context *ctx)
 struct ast *parse_and_or(struct lexer_context *ctx)
 {
     struct ast *result = parse_pipeline(ctx);
+    if (result == NULL)
+        return NULL;
     struct token *token = PEEK_TOKEN();
 
-    if (token->type == TOKEN_AND || token->type == TOKEN_OR)
+    while (token->type == TOKEN_AND || token->type == TOKEN_OR)
     {
-        // set left part
+        // Set left part
 
         struct ast *left = result;
 
         // eat and_or token
         token = POP_TOKEN();
 
-        // set type
+        // Set type
         enum ast_and_or_type type = and_or_tok_to_ast(token->type);
 
         token = PEEK_TOKEN();
 
-        // skip newlines
+        // Skip newlines
         while (token->type == TOKEN_NEWLINE)
         {
             token = POP_TOKEN();
             token = PEEK_TOKEN();
         }
 
-        // right part
+        // Right part
         struct ast *right = parse_pipeline(ctx);
 
         result = ast_create_and_or(left, right, type);
+        if (result == NULL)
+        {
+            ast_free(&left);
+            ast_free(&right);
+            return NULL;
+        }
     }
 
     return result;
@@ -164,53 +123,92 @@ struct ast *parse_command(struct lexer_context *ctx)
     }
     else
     {
-        return ast_create_void(); // TODO not sure what to do
+        puts("Syntax error: expected command");
+        return NULL;
     }
 }
 
 struct ast *parse_simple_command(struct lexer_context *ctx)
 {
     struct list *command_elements = NULL;
-    struct token *token = PEEK_TOKEN();
+
+    // WORD
+    struct token *token = POP_TOKEN();
     if (token->type != TOKEN_WORD)
     {
         puts("Expected a command but got a different token type");
         return NULL;
     }
+    char *command = strdup(token->data);
+    command_elements = list_append(command_elements, command);
 
-    while (token->type == TOKEN_WORD)
+    token = PEEK_TOKEN();
+
+    // Eventual elements
+    while (is_first(*token, RULE_ELEMENT))
     {
-        token = pop_token(ctx);
-        if (token == NULL)
+        // Get element
+        struct ast *element = parse_element(ctx);
+        if (element == NULL)
         {
-            // TODO free
+            list_deep_destroy(command_elements);
             return NULL;
         }
-        char *word = strdup(token->data);
-        if (word == NULL)
+
+        // Get element type
+        if (ast_is_word(element))
         {
-            // TODO free
-            puts("Internal error: Couldn't copy token content (is memory full "
-                 "?)");
+            struct ast_word *element_word = ast_get_word(element);
+            command_elements =
+                list_append(command_elements, element_word->word);
+        }
+        else if (ast_is_redir(element))
+        {
+            // TODO
+            puts("NOT IMPLEMENTED");
             return NULL;
         }
-        command_elements = list_append(command_elements, word);
-        token = peek_token(ctx);
-        if (token == NULL)
+        else
         {
-            // TODO free
+            puts("Internal error: unexpected return value from parse_element "
+                 "in parse_simple_command");
+            list_deep_destroy(command_elements);
             return NULL;
         }
+
+        // Forward
+        token = PEEK_TOKEN();
     }
 
+    // Result
     struct ast *result = ast_create_command(command_elements);
     if (result == NULL)
     {
-        // TODO free
+        list_deep_destroy(command_elements);
+        return NULL;
     }
     return result;
 }
 
+struct ast *parse_element(struct lexer_context *ctx)
+{
+    struct token *token = PEEK_TOKEN();
+    if (token->type == TOKEN_WORD)
+    {
+        token = POP_TOKEN();
+        return ast_create_word(token->data);
+    }
+    else if (token->type == TOKEN_IONUMBER || token->type == TOKEN_REDIRECTION)
+    {
+        return parse_redirection(ctx);
+    }
+    else
+    {
+        puts("Syntax error: unexpected token at parse_element");
+        return NULL;
+    }
+}
+
 struct ast *parse_shell_command(struct lexer_context *ctx)
 {
     return parse_if_rule(ctx);
@@ -257,6 +255,7 @@ struct ast *parse_if_rule(struct lexer_context *ctx)
         return NULL;
     }
 
+    // Fi keyword
     token = POP_TOKEN();
     if (token->type != TOKEN_FI)
     {
@@ -267,6 +266,7 @@ struct ast *parse_if_rule(struct lexer_context *ctx)
         return NULL;
     }
 
+    // Result
     struct ast *result =
         ast_create_if(condition_content, then_content, else_content);
     if (result == NULL)
@@ -294,7 +294,7 @@ struct ast *parse_compound_list(struct lexer_context *ctx)
         token = PEEK_TOKEN();
     }
 
-    // and_or
+    // And/or
     current_cmd = parse_and_or(ctx);
     if (current_cmd == NULL)
         return NULL;
@@ -314,12 +314,15 @@ struct ast *parse_compound_list(struct lexer_context *ctx)
             token = PEEK_TOKEN();
         }
 
-        // and_or
-        current_cmd = parse_and_or(ctx);
-        if (current_cmd == NULL)
-            return NULL;
-        result_list = list_append(result_list, current_cmd);
-
+        // And/or
+        if (is_first(*token, RULE_AND_OR))
+        {
+            current_cmd = parse_and_or(ctx);
+            if (current_cmd == NULL)
+                return NULL;
+            result_list = list_append(result_list, current_cmd);
+        }
+        
         token = PEEK_TOKEN();
     }
 
@@ -352,7 +355,7 @@ struct ast *parse_else_clause(struct lexer_context *ctx)
         token = POP_TOKEN();
         struct ast *condition = parse_compound_list(ctx);
 
-        // 'then'
+        // Then keyword
         token = POP_TOKEN();
         if (token->type != TOKEN_THEN)
         {
diff --git a/src/parser/grammar_basic.h b/src/parser/grammar_basic.h
new file mode 100644
index 0000000..f1c2f77
--- /dev/null
+++ b/src/parser/grammar_basic.h
@@ -0,0 +1,112 @@
+#ifndef GRAMMAR_BASIC_H
+#define GRAMMAR_BASIC_H
+
+#include "../lexer/lexer.h"
+#include "../utils/ast/ast.h"
+
+// === Functions
+
+/*
+ * @brief parses a list of [and_or] rules separated by semicolons and that
+ *         ends by a newline
+ *
+ * @code list = and_or { ';' and_or } [ ';' ] ;
+ *
+ * @first first(and_or)
+ */
+struct ast *parse_list(struct lexer_context *ctx);
+
+/*
+ * @brief Only parses a pipeline rule for the moment
+ *
+ * @code and_or = pipeline { ( '&&' | '||' ) {'\n'} pipeline } ;
+ *
+ * @first first(pipeline)
+ */
+struct ast *parse_and_or(struct lexer_context *ctx);
+
+/*
+ * @brief Only parses a command rule for the moment
+ *
+ * @code pipeline = command ;
+ *
+ * @first first(command)
+ */
+struct ast *parse_pipeline(struct lexer_context *ctx);
+
+/*
+ * @brief Parses a simple command rule or a shell command rule depending on
+ *        the first token.
+ * @note
+ *        TOKEN_WORD => simple_command
+ *        TOKEN_IF => shell_command
+ *
+ * @code command = simple_command
+ *               | shell_command
+ *               ;
+ * @first first(simple_command), first(shell_command)
+ */
+struct ast *parse_command(struct lexer_context *ctx);
+
+/*
+ * @brief Parses a simple list of words (command and arguments)
+ *        ending by a separator
+ *
+ * @code simple_command = WORD { element } ;
+ *
+ * @first WORD
+ */
+struct ast *parse_simple_command(struct lexer_context *ctx);
+
+/*
+ * @brief Parses an element rule
+ *
+ * @code element = WORD
+ *               | redirection
+ *               ;
+ *
+ * @first WORD, first(redirection)
+ */
+struct ast *parse_element(struct lexer_context *ctx);
+
+/*
+ * @brief Only parses if rules for the moment
+ *
+ * @code shell_command = if_rule ;
+ *
+ * @first first(if_rule)
+ */
+struct ast *parse_shell_command(struct lexer_context *ctx);
+
+/*
+ * @brief Parses a if rule (condition, then-clause, elif-clause, else-clause)
+ *
+ * @code if_rule = 'if' compound_list 'then' compound_list [else_clause] 'fi' ;
+ *
+ * @first TOKEN_IF
+ */
+struct ast *parse_if_rule(struct lexer_context *ctx);
+
+/*
+ * @brief parses commands inside if/else clauses and returns the corresponding
+ * AST list
+ *
+ * @code compound_list = {'\n'} and_or { ( ';' | '\n' ) {'\n'} and_or } [';']
+ * {'\n'} ;
+ *
+ * @first TOKEN_NEWLINE, first(and_or)
+ */
+struct ast *parse_compound_list(struct lexer_context *ctx);
+
+/*
+ * @brief
+ *
+ * @code else_clause = 'else' compound_list
+ *                   | 'elif' compound_list 'then' compound_list [else_clause]
+ *                   ;
+ *
+ * @first TOKEN_ELSE, TOKEN_ELIF
+ */
+struct ast *parse_else_clause(struct lexer_context *ctx);
+
+#endif /* ! GRAMMAR_BASIC_H */
diff --git a/src/parser/parser.c b/src/parser/parser.c
index dbe3f72..b86c696 100644
--- a/src/parser/parser.c
+++ b/src/parser/parser.c
@@ -1,49 +1,52 @@
 #include "parser.h"
 
-#include <stdbool.h>
-#include <stddef.h>
 #include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 
-#include "../lexer/lexer.h"
-#include "../parser/parsing_utils.h"
-#include "../utils/lists/lists.h"
+#include "grammar.h"
 
-// === Static functions
-// ...
+// === Static variables
+
+static enum parser_state state = PARSER_STATE_NOT_INITIALIZED;
 
 // === Functions
 
+bool parser_init(void)
+{
+    if (state == PARSER_STATE_READY)
+    {
+        puts("Internal error: tried to initialize the parser module twice.");
+        return NULL;
+    }
+    int success = grammar_init();
+    if (success == false)
+        return false;
+
+    state = PARSER_STATE_READY;
+    return true;
+}
+
 struct ast *get_ast(struct lexer_context *ctx)
 {
-    struct token *token = PEEK_TOKEN();
-    struct ast *res;
-
-    if (token->type == TOKEN_EOF)
+    if (ctx == NULL)
     {
-        token = pop_token(ctx);
-        return ast_create_end();
+        puts("Internal error: called parser with no lexer context (NULL "
+             "pointer). Aborting.");
+        return NULL;
     }
-    else if (token->type == TOKEN_NEWLINE)
+    if (state == PARSER_STATE_NOT_INITIALIZED)
     {
-        token = pop_token(ctx);
-        return ast_create_void();
+        puts("Internal error: attempted to call parser without initializing "
+             "it. Aborting.");
+        return NULL;
     }
-    else // TOKEN WORD
+    if (state == PARSER_STATE_CLOSED)
     {
-        res = parse_list(ctx);
+        puts("Internal error: attempted to call parser after closing it. "
+             "Aborting.");
+        return NULL;
     }
 
-    /*
-       if (token == NULL)
-       {
-       puts("Internal error: cannot get the following token");
-       puts("Hint: EOF might be missing");
-       return NULL;
-       }
-       */
-    return res;
+    return parse_input(ctx);
 }
 
 // TODO
@@ -51,4 +54,4 @@ struct ast *get_ast_str(char *command)
 {
     (void)command;
     return NULL;
-}
\ No newline at end of file
+}
diff --git a/src/parser/parser.h b/src/parser/parser.h
index 1837e75..a79497b 100644
--- a/src/parser/parser.h
+++ b/src/parser/parser.h
@@ -1,9 +1,29 @@
 #ifndef PARSER_H
 #define PARSER_H
 
+#include <stdbool.h>
+
 #include "../lexer/lexer.h"
 #include "../utils/ast/ast.h"
 
+enum parser_state
+{
+    PARSER_STATE_NOT_INITIALIZED = 0,
+    PARSER_STATE_READY,
+    PARSER_STATE_CLOSED
+};
+
+/* @brief Initializes the parser module
+ * @warning parser needs to be closed after use with parser_close()
+ *
+ * @return Returns false on error and true on success
+ */
+bool parser_init(void);
+
+/* @brief Closes the parser module after use
+ */
+void parser_close(void);
+
 /* @brief Builds the AST representation of the next command to execute.
  *
  * @return Returns the AST representation of the next command to execute.
diff --git a/src/parser/parsing_utils.h b/src/parser/parsing_utils.h
deleted file mode 100644
index 89eb4bf..0000000
--- a/src/parser/parsing_utils.h
+++ /dev/null
@@ -1,100 +0,0 @@
-#ifndef PARSING_UTILS_H
-#define PARSING_UTILS_H
-
-#include "../lexer/lexer.h"
-
-// === Macros
-
-#define PEEK_TOKEN()                                                           \
-    peek_token(ctx);                                                           \
-    if (token == NULL)                                                         \
-    {                                                                          \
-        puts("Internal error: cannot get the following token");                \
-        return NULL;                                                           \
-    }
-
-#define POP_TOKEN()                                                            \
-    pop_token(ctx);                                                            \
-    if (token == NULL)                                                         \
-    {                                                                          \
-        puts("Internal error: cannot get the following token");                \
-        return NULL;                                                           \
-    }
-
-/* @brief Acts as the entry point of the parser, calls parse_list
- *
- * @code input = list '\n'
- *             | list EOF
- *             | '\n'
- *             | EOF
- *             ;
- */
-struct ast *parse_input(struct lexer_context *ctx);
-
-/* @brief: parses a list of [and_or] rules separated by semicolons and that
- *         ends by a newline
- *
- * @code list = and_or { ';' and_or } [ ';' ] ;
- */
-struct ast *parse_list(struct lexer_context *ctx);
-
-/* @brief Only parses a pipeline rule for the moment
- *
- * @code and_or = pipeline ;
- */
-struct ast *parse_and_or(struct lexer_context *ctx);
-
-/* @brief Only parses a command rule for the moment
- *
- * @code pipeline = command ;
- */
-struct ast *parse_pipeline(struct lexer_context *ctx);
-
-/* @brief Parses a simple command rule or a shell command rule depending on
- *        the first token.
- * @note
- *        TOKEN_WORD => simple_command
- *        TOKEN_IF => shell_command
- *
- * @code command = simple_command
- *               | shell_command
- *               ;
- */
-struct ast *parse_command(struct lexer_context *ctx);
-
-/* @brief Parses a simple list of words (command and arguments)
- *        ending by a separator
- *
- * @code simple_command = WORD { element } ;
- */
-struct ast *parse_simple_command(struct lexer_context *ctx);
-
-/* @brief Only parses if rules for the moment
- *
- * @code shell_command = if_rule ;
- */
-struct ast *parse_shell_command(struct lexer_context *ctx);
-
-/* @brief Parses a if rule (condition, then-clause, elif-clause, else-clause)
- *
- * @code if_rule = 'if' compound_list 'then' compound_list [else_clause] 'fi' ;
- */
-struct ast *parse_if_rule(struct lexer_context *ctx);
-
-/* @brief parses commands inside if/else clauses and returns the corresponding
- * AST list
- *
- * @code compound_list = {'\n'} and_or { ( ';' | '\n' ) {'\n'} and_or } [';']
- * {'\n'} ;
- */
-struct ast *parse_compound_list(struct lexer_context *ctx);
-
-/* @brief
- *
- * @code else_clause = 'else' compound_list
- *                   | 'elif' compound_list 'then' compound_list [else_clause]
- *                   ;
- */
-struct ast *parse_else_clause(struct lexer_context *ctx);
-
-#endif /* ! PARSING_UTILS_H */
diff --git a/src/utils/ast/ast.c b/src/utils/ast/ast.c
index ae042ee..b4afb9c 100644
--- a/src/utils/ast/ast.c
+++ b/src/utils/ast/ast.c
@@ -10,7 +10,7 @@
 
 void ast_free(struct ast **node)
 {
-    if (*node == NULL)
+    if (node == NULL || *node == NULL)
         return;
     // ast void does not need to be freed.
     if (ast_is_if(*node))
diff --git a/src/utils/ast/ast.h b/src/utils/ast/ast.h
index a98d88b..fc35666 100644
--- a/src/utils/ast/ast.h
+++ b/src/utils/ast/ast.h
@@ -9,6 +9,7 @@
 #include "ast_list.h"
 #include "ast_redir.h"
 #include "ast_void.h"
+#include "ast_word.h"
 
 /**
  * Prints the Graphviz DOT representation of the given AST to stdout.
diff --git a/src/utils/ast/ast_base.h b/src/utils/ast/ast_base.h
index e09b25d..4ae00ec 100644
--- a/src/utils/ast/ast_base.h
+++ b/src/utils/ast/ast_base.h
@@ -11,7 +11,8 @@ enum ast_type
     AST_AND_OR,
     AST_REDIR,
     AST_VOID,
-    AST_CMD
+    AST_CMD,
+    AST_WORD
 };
 
 struct ast
diff --git a/src/utils/ast/ast_word.c b/src/utils/ast/ast_word.c
new file mode 100644
index 0000000..d798c77
--- /dev/null
+++ b/src/utils/ast/ast_word.c
@@ -0,0 +1,45 @@
+#include "ast_word.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct ast *ast_create_word(char *word)
+{
+    struct ast_word *ast_node = malloc(sizeof(struct ast_word));
+    if (ast_node == NULL)
+        return NULL;
+
+    ast_node->type = AST_WORD;
+    ast_node->word = strdup(word);
+    struct ast *res = ast_create(AST_WORD, ast_node);
+    if (res == NULL)
+    {
+        free(ast_node);
+        return NULL;
+    }
+
+    return res;
+}
+
+struct ast_word *ast_get_word(struct ast *node)
+{
+    if (node == NULL || node->type != AST_WORD)
+        return NULL;
+
+    return node->data;
+}
+
+bool ast_is_word(struct ast *node)
+{
+    return node && node->type == AST_WORD;
+}
+
+void ast_free_word(struct ast_word *ast_node)
+{
+    if (ast_node == NULL)
+        return;
+
+    free(ast_node->word);
+    free(ast_node);
+}
diff --git a/src/utils/ast/ast_word.h b/src/utils/ast/ast_word.h
new file mode 100644
index 0000000..d5e0e1d
--- /dev/null
+++ b/src/utils/ast/ast_word.h
@@ -0,0 +1,35 @@
+#ifndef AST_WORD_H
+#define AST_WORD_H
+
+#include <stdbool.h>
+
+#include "ast_base.h"
+
+struct ast_word
+{
+    enum ast_type type;
+    char *word;
+};
+
+/**
+ * Checks if the given AST node is a command.
+ */
+bool ast_is_word(struct ast *node);
+
+/**
+ * Retrieves the command data from the given AST node.
+ * Assumes that the node is of type AST_CMD.
+ */
+struct ast_word *ast_get_word(struct ast *node);
+
+/**
+ * Creates a new AST node representing a command.
+ */
+struct ast *ast_create_word(char* word);
+
+/*
+ * @brief: frees the given ast_command and sets the pointer to NULL.
+ */
+void ast_free_word(struct ast_word *ast_node);
+
+#endif /* ! AST_WORD_H */