diff --git a/src/templates_front/templator_front.org b/src/templates_front/templator_front.org
index 5e0096a..fb517ad 100644
--- a/src/templates_front/templator_front.org
+++ b/src/templates_front/templator_front.org
@@ -688,29 +688,6 @@ interface
 end interface
     #+end_src
 
-** C helper functions
-
-    #+begin_src c :tangle prefix_front.c
-trexio_exit_code transform_str (char** dest, const char** src, uint64_t str_max_num, uint32_t str_max_len){
-
-  if (dest == NULL)  return TREXIO_INVALID_ARG_1;
-  assert (str_max_num > 0);
-  assert (str_max_len > 0);
-
-  char* tmp_str = (char*)calloc(str_max_num*(str_max_len+1)+1,sizeof(char));
-
-  for (int i=0; i<str_max_num; i++){
-    dest[i] = tmp_str;
-    strncpy(tmp_str, src[i], str_max_len);
-    tmp_str += str_max_len + 1;
-  }
-
-  /*tmp_str cannot be freed here but it is taken case of when pointer to dest is deallocated */
-
-  return TREXIO_SUCCESS;
-}
-    #+end_src
-
 * Templates for front end
 ** Description
 
@@ -779,7 +756,7 @@ trexio_exit_code transform_str (char** dest, const char** src, uint64_t str_max_
    *read* and *write* functionality.  TREXIO supports I/O with single
    or double precision for integer and floating point numbers.
 
-** Templates for front end has/read/write a dimension
+** Templates for front end has/read/write a single dimensioning variable
 
    This section concerns API calls related to dimensioning variables.
 
@@ -854,26 +831,23 @@ trexio_write_$group_num$_64 (trexio_t* const file, const int64_t num)
   if (file == NULL) return TREXIO_INVALID_ARG_1;
   if (num  <  0   ) return TREXIO_INVALID_ARG_2;
 
-  trexio_exit_code rc = TREXIO_GROUP_WRITE_ERROR;
-
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    rc = trexio_text_write_$group_num$(file, (int64_t) num);
+    return trexio_text_write_$group_num$(file, (int64_t) num);
     break;
 
   case TREXIO_HDF5:
-    rc = trexio_hdf5_write_$group_num$(file, (int64_t) num);
+    return trexio_hdf5_write_$group_num$(file, (int64_t) num);
     break;
 /*
   case TREXIO_JSON:
-    rc = trexio_json_write_$group_num$(file, (int64_t) num);
+    return trexio_json_write_$group_num$(file, (int64_t) num);
     break;
 ,*/
   }
-  if (rc != TREXIO_SUCCESS) return rc;
 
-  return TREXIO_SUCCESS;
+  return TREXIO_FAILURE;
 }
      #+end_src
 
@@ -917,26 +891,23 @@ trexio_write_$group_num$_32 (trexio_t* const file, const int32_t num)
   if (file == NULL) return TREXIO_INVALID_ARG_1;
   if (num  <  0   ) return TREXIO_INVALID_ARG_2;
 
-  trexio_exit_code rc = TREXIO_GROUP_WRITE_ERROR;
-
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    rc = trexio_text_write_$group_num$(file, (int64_t) num);
+    return trexio_text_write_$group_num$(file, (int64_t) num);
     break;
 
   case TREXIO_HDF5:
-    rc = trexio_hdf5_write_$group_num$(file, (int64_t) num);
+    return trexio_hdf5_write_$group_num$(file, (int64_t) num);
     break;
 /*
   case TREXIO_JSON:
-    rc = trexio_json_write_$group_num$(file, (int64_t) num);
+    return trexio_json_write_$group_num$(file, (int64_t) num);
     break;
 ,*/
   }
-  if (rc != TREXIO_SUCCESS) return rc;
 
-  return TREXIO_SUCCESS;
+  return TREXIO_FAILURE;
 }
      #+end_src
 
@@ -980,8 +951,8 @@ trexio_has_$group_num$ (trexio_t* const file)
     break;
 ,*/
   }
-  return TREXIO_FAILURE;
 
+  return TREXIO_FAILURE;
 }
      #+end_src
 
@@ -1411,7 +1382,7 @@ end interface
      #+end_src
 
 ** Templates for front end has/read/write a dataset of strings
-
+*** Introduction
    This section concerns API calls related to datasets of strings.
 
    | Function name               | Description                         |
@@ -1622,6 +1593,145 @@ interface
 end interface
      #+end_src
 
+** Templates for front end has/read/write a single string attribute
+*** Introduction
+
+   This section concerns API calls related to string attributes.
+
+   | Function name              | Description                                  |
+   |----------------------------+----------------------------------------------|
+   | ~trexio_has_$group_str$~   | Check if a string attribute exists in a file |
+   | ~trexio_read_$group_str$~  | Read a string attribute                      |
+   | ~trexio_write_$group_str$~ | Write a string attribute                     |
+
+*** C templates for front end
+
+     #+begin_src c :tangle hrw_attr_str_front.h :exports none
+trexio_exit_code trexio_has_$group_str$(trexio_t* const file);
+trexio_exit_code trexio_read_$group_str$(trexio_t* const file, char* const str);
+trexio_exit_code trexio_write_$group_str$(trexio_t* const file, const char* str);
+     #+end_src
+
+     #+begin_src c :tangle read_attr_str_front.c
+trexio_exit_code
+trexio_read_$group_str$ (trexio_t* const file, char* const str)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  if (str  == NULL) return TREXIO_INVALID_ARG_2;
+
+  switch (file->back_end) {
+
+  case TREXIO_TEXT:
+    //return trexio_text_read_$group_str$(file, str);
+    break;
+
+  case TREXIO_HDF5:
+    return trexio_hdf5_read_$group_str$(file, str);
+    break;
+/*
+  case TREXIO_JSON:
+    return trexio_json_read_$group_str$(file, str);
+    break;
+,*/
+  }
+
+  return TREXIO_FAILURE;
+}
+     #+end_src
+
+     #+begin_src c :tangle write_attr_str_front.c
+trexio_exit_code
+trexio_write_$group_str$ (trexio_t* const file, const char* str)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  if (str  == NULL) return TREXIO_INVALID_ARG_2;
+
+  switch (file->back_end) {
+
+  case TREXIO_TEXT:
+    //return trexio_text_write_$group_str$(file, str);
+    break;
+
+  case TREXIO_HDF5:
+    return trexio_hdf5_write_$group_str$(file, str);
+    break;
+/*
+  case TREXIO_JSON:
+    return trexio_json_write_$group_str$(file, str);
+    break;
+,*/
+  }
+
+  return TREXIO_FAILURE;
+}
+     #+end_src
+   
+     #+begin_src c :tangle has_attr_str_front.c
+trexio_exit_code
+trexio_has_$group_str$ (trexio_t* const file)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  assert(file->back_end < TREXIO_INVALID_BACK_END);
+
+  switch (file->back_end) {
+
+  case TREXIO_TEXT:
+    //return trexio_text_has_$group_str$(file);
+    break;
+
+  case TREXIO_HDF5:
+    return trexio_hdf5_has_$group_str$(file);
+    break;
+/*
+  case TREXIO_JSON:
+    return trexio_json_has_$group_str$(file);
+    break;
+,*/
+  }
+  return TREXIO_FAILURE;
+
+}
+     #+end_src
+
+*** Fortran templates for front end
+
+    The ~Fortran~ templates that provide an access to the ~C~ API calls from Fortran.
+    These templates are based on the use of ~iso_c_binding~. Pointers have to be passed by value.
+
+    
+     #+begin_src f90 :tangle write_attr_str_front_fortran.f90
+interface
+   integer function trexio_write_$group_str$ (trex_file, str) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     character, intent(in) :: str(*)
+   end function trexio_write_$group_str$
+end interface
+     #+end_src
+
+     #+begin_src f90 :tangle read_attr_str_front_fortran.f90
+interface
+   integer function trexio_read_$group_str$ (trex_file, str) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     character, intent(out) :: str(*)
+   end function trexio_read_$group_str$
+end interface
+     #+end_src
+
+     #+begin_src f90 :tangle has_attr_str_front_fortran.f90
+interface
+   integer function trexio_has_$group_str$ (trex_file) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+   end function trexio_has_$group_str$
+end interface
+     #+end_src
+
 * Fortran helper/wrapper functions
 
   The function below adapts the original C-based ~trexio_open~ for Fortran.
diff --git a/src/templates_hdf5/templator_hdf5.org b/src/templates_hdf5/templator_hdf5.org
index 62f1e58..2680f9b 100644
--- a/src/templates_hdf5/templator_hdf5.org
+++ b/src/templates_hdf5/templator_hdf5.org
@@ -56,6 +56,7 @@
 #define $GROUP$_GROUP_NAME          "$group$"
 #define $GROUP_NUM$_NAME            "$group_num$"
 #define $GROUP_DSET$_NAME           "$group_dset$"
+#define $GROUP_STR$_NAME            "$group_str$"
   #+end_src
 
 ** Template for HDF5 structures
@@ -155,7 +156,7 @@ trexio_hdf5_deinit (trexio_t* const file)
 }
   #+end_src
 
-** Template for HDF5 has/read/write a number
+** Template for HDF5 has/read/write a single dimensioning variable
 
   #+begin_src c :tangle hrw_num_hdf5.h :exports none
 trexio_exit_code trexio_hdf5_has_$group_num$ (trexio_t* const file);
@@ -176,11 +177,14 @@ trexio_hdf5_read_$group_num$ (trexio_t* const file, uint64_t* const num)
   /* Quit if the dimensioning attribute is missing in the file */
   if (H5Aexists(f->$group$_group, $GROUP_NUM$_NAME) == 0) return TREXIO_FAILURE;
 
-  /* Read the nucleus_num attribute of nucleus group */
+  /* Read the $group_num$ attribute of $group$ group */
   const hid_t num_id = H5Aopen(f->$group$_group, $GROUP_NUM$_NAME, H5P_DEFAULT);
   if (num_id <= 0) return TREXIO_INVALID_ID;
 
   const herr_t status = H5Aread(num_id, H5T_NATIVE_UINT64, num);
+
+  H5Aclose(num_id);
+
   if (status < 0) return TREXIO_FAILURE;
 
   return TREXIO_SUCCESS;
@@ -623,7 +627,132 @@ trexio_hdf5_has_$group_dset$ (trexio_t* const file)
 
 }
    #+end_src
+   
+** Template for HDF5 has/read/write a single string attribute
 
+  #+begin_src c :tangle hrw_attr_str_hdf5.h :exports none
+trexio_exit_code trexio_hdf5_has_$group_str$ (trexio_t* const file);
+trexio_exit_code trexio_hdf5_read_$group_str$ (trexio_t* const file, char* const str);
+trexio_exit_code trexio_hdf5_write_$group_str$(trexio_t* const file, const char* str);
+  #+end_src
+
+
+  #+begin_src c :tangle read_attr_str_hdf5.c
+trexio_exit_code
+trexio_hdf5_read_$group_str$ (trexio_t* const file, char* const str)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  if (str  == NULL) return TREXIO_INVALID_ARG_2;
+
+  const trexio_hdf5_t* f = (const trexio_hdf5_t*) file;
+  /* Quit if the string attribute is missing in the file */
+  if (H5Aexists(f->$group$_group, $GROUP_STR$_NAME) == 0) return TREXIO_HAS_NOT;
+
+  /* Read the $group_str$ attribute of $group$ group */
+  const hid_t str_id = H5Aopen(f->$group$_group, $GROUP_STR$_NAME, H5P_DEFAULT);
+  if (str_id <= 0) return TREXIO_INVALID_ID;
+
+  const hid_t ftype_id = H5Aget_type(str_id);
+  if (ftype_id <= 0) return TREXIO_INVALID_ID;
+  uint64_t sdim = H5Tget_size(ftype_id);
+  if (sdim <= 0) return TREXIO_FAILURE;
+  sdim++;                         /* Make room for null terminator */
+
+  const hid_t mem_id = H5Tcopy(H5T_C_S1);
+  if (mem_id <= 0) return TREXIO_INVALID_ID;
+
+  herr_t status;
+  status = H5Tset_size(mem_id, sdim);
+  if (status < 0) return TREXIO_FAILURE;
+
+  status = H5Aread(str_id, mem_id, str);
+  if (status < 0) return TREXIO_FAILURE;
+
+  H5Aclose(str_id);
+  H5Tclose(mem_id);
+  H5Tclose(ftype_id);
+
+  return TREXIO_SUCCESS;
+
+}
+   #+end_src
+
+
+  #+begin_src c :tangle write_attr_str_hdf5.c
+trexio_exit_code
+trexio_hdf5_write_$group_str$ (trexio_t* const file, const char* str)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  if (str  == NULL) return TREXIO_INVALID_ARG_2;
+
+  trexio_hdf5_t* const f = (trexio_hdf5_t*) file;
+
+
+  /* Setup the dataspace */
+  const hid_t dtype_id = H5Tcopy(H5T_C_S1);
+  if (dtype_id <= 0) return TREXIO_INVALID_ID;
+
+  size_t str_attr_len = strlen(str) + 1;
+
+  herr_t status;
+  status = H5Tset_size(dtype_id, str_attr_len);
+  if (status < 0) return TREXIO_FAILURE;
+
+  status = H5Tset_strpad(dtype_id, H5T_STR_NULLTERM);
+  if (status < 0) return TREXIO_FAILURE;
+
+  const hid_t dspace_id = H5Screate(H5S_SCALAR);
+  if (dspace_id <= 0) return TREXIO_INVALID_ID;
+  
+  /* Create the $group_str$ attribute of $group$ group */
+  const hid_t str_id = H5Acreate(f->$group$_group, $GROUP_STR$_NAME, dtype_id, dspace_id,
+                       H5P_DEFAULT, H5P_DEFAULT);
+
+  if (str_id <= 0) {
+    H5Sclose(dspace_id);
+    H5Tclose(dtype_id);
+    return TREXIO_INVALID_ID;
+  }
+  
+  status = H5Awrite(str_id, dtype_id, str);
+  if (status < 0) {
+    H5Aclose(str_id);
+    H5Sclose(dspace_id);
+    H5Tclose(dtype_id);
+    return TREXIO_FAILURE;
+  }
+  
+  H5Aclose(str_id);
+  H5Sclose(dspace_id);
+  H5Tclose(dtype_id);
+  return TREXIO_SUCCESS;
+
+}
+    #+end_src
+
+  #+begin_src c :tangle has_attr_str_hdf5.c
+trexio_exit_code
+trexio_hdf5_has_$group_str$ (trexio_t* const file)
+{
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  const trexio_hdf5_t* f = (const trexio_hdf5_t*) file;
+
+  htri_t status = H5Aexists(f->$group$_group, $GROUP_STR$_NAME);
+  /* H5Aexists returns positive value if attribute exists, 0 if does not, negative if error */
+  if (status > 0){
+    return TREXIO_SUCCESS;
+  } else if (status == 0) {
+    return TREXIO_HAS_NOT;
+  } else {
+    return TREXIO_FAILURE;
+  }
+
+}
+    #+end_src
 * Constant file suffixes (not used by the generator)               :noexport:
 
   #+begin_src c :tangle suffix_hdf5.h