Add cd -

src/builtins.c

@@ -88,11 +88,33 @@ void cd_print_error(void)
     }
 }
 
+static
+int builtins_cd_chdir(char *path, history_t *history, char **args, env_t *env)
+{
+    bool last_chdir_set = false;
+
+    if (history->last_chdir != NULL && u_strcmp(args[1], "-") == 0) {
+        path = history->last_chdir;
+        free(history->last_chdir);
+        history->last_chdir = u_strdup(get_env_value(env, "PWD"));
+        last_chdir_set = true;
+    }
+    if (chdir(path) < 0) {
+        write(STDERR_FILENO, path, u_strlen(path));
+        cd_print_error();
+        return RETURN_FAILURE;
+    }
+    if (!last_chdir_set) {
+        free(history->last_chdir);
+        history->last_chdir = u_strdup(path);
+    }
+    return RETURN_SUCCESS;
+}
+
 int builtins_cd(env_t *env, char **args, char *buff __attribute__((unused)),
     history_t *history __attribute__((unused)))
 {
     char *path = args[1];
-    int result = RETURN_SUCCESS;
 
     if (path == NULL || u_strcmp(args[1], "~") == 0)
         path = get_env_value(env, "HOME");
@@ -102,10 +124,5 @@ int builtins_cd(env_t *env, char **args, char *buff __attribute__((unused)),
         WRITE_CONST(STDERR_FILENO, "cd: Too many arguments.\n");
         return RETURN_FAILURE;
     }
-    if (chdir(path) < 0) {
-        write(STDERR_FILENO, path, u_strlen(path));
-        cd_print_error();
-        result = RETURN_FAILURE;
-    }
-    return result;
+    return builtins_cd_chdir(path, history, args, env);
 }

src/shell.c

@@ -56,7 +56,7 @@ int shell_loop(env_t *env, int is_a_tty, history_t *history)
 int shell(char **env_ptr)
 {
     env_t env = parse_env(env_ptr);
-    history_t history = { .cmd_history = NULL, 0 };
+    history_t history = { .cmd_history = NULL, 0, .last_chdir = NULL };
     int shell_result;
 
     if (!env.env)

src/shell.h

@@ -13,6 +13,7 @@
 typedef struct {
     char **cmd_history;
     int last_exit_code;
+    char *last_chdir;
 } history_t;
 int shell(char **env);
 #endif /* SHELL_H */

ulib/str/strdup.c

@@ -15,6 +15,8 @@ char *u_strdup(char const *src)
     char *dest;
     int len = u_strlen(src);
 
+    if (!len)
+        return NULL;
     dest = malloc(sizeof(char) * (len + 1));
     if (dest == NULL)
         return NULL;