diff --git a/src/MPIIO/dump_custom_mpiio.cpp b/src/MPIIO/dump_custom_mpiio.cpp
index 68c5896361..766bd976bc 100644
--- a/src/MPIIO/dump_custom_mpiio.cpp
+++ b/src/MPIIO/dump_custom_mpiio.cpp
@@ -232,48 +232,36 @@ void DumpCustomMPIIO::init_style()
   // format = copy of default or user-specified line format
 
   delete[] format;
-  char *str;
-  if (format_line_user)
-    str = format_line_user;
-  else
-    str = format_default;
-
-  int n = strlen(str) + 1;
-  format = new char[n];
-  strcpy(format, str);
+  if (format_line_user) format = utils::strdup(format_line_user);
+  else format = utils::strdup(format_default);
 
   // tokenize the format string and add space at end of each format element
   // if user-specified int/float format exists, use it instead
   // if user-specified column format exists, use it instead
   // lo priority = line, medium priority = int/float, hi priority = column
 
-  char *ptr;
-  for (int i = 0; i < size_one; i++) {
-    if (i == 0)
-      ptr = strtok(format, " \0");
-    else
-      ptr = strtok(nullptr, " \0");
-    if (ptr == nullptr) error->all(FLERR, "Dump_modify format line is too short");
+  auto words = utils::split_words(format);
+  if ((int) words.size() < nfield)
+    error->all(FLERR,"Dump_modify format line is too short");
+
+  int i=0;
+  for (const auto &word : words) {
     delete[] vformat[i];
 
-    if (format_column_user[i]) {
-      vformat[i] = new char[strlen(format_column_user[i]) + 2];
-      strcpy(vformat[i], format_column_user[i]);
-    } else if (vtype[i] == Dump::INT && format_int_user) {
-      vformat[i] = new char[strlen(format_int_user) + 2];
-      strcpy(vformat[i], format_int_user);
-    } else if (vtype[i] == Dump::DOUBLE && format_float_user) {
-      vformat[i] = new char[strlen(format_float_user) + 2];
-      strcpy(vformat[i], format_float_user);
-    } else if (vtype[i] == Dump::BIGINT && format_bigint_user) {
-      vformat[i] = new char[strlen(format_bigint_user) + 2];
-      strcpy(vformat[i], format_bigint_user);
-    } else {
-      vformat[i] = new char[strlen(ptr) + 2];
-      strcpy(vformat[i], ptr);
-    }
+    if (format_column_user[i])
+      vformat[i] = utils::strdup(std::string(format_column_user[i]) + " ");
+    else if (vtype[i] == Dump::INT && format_int_user)
+      vformat[i] = utils::strdup(std::string(format_int_user) + " ");
+    else if (vtype[i] == Dump::DOUBLE && format_float_user)
+      vformat[i] = utils::strdup(std::string(format_float_user) + " ");
+    else if (vtype[i] == Dump::BIGINT && format_bigint_user)
+      vformat[i] = utils::strdup(std::string(format_bigint_user) + " ");
+    else vformat[i] = utils::strdup(word + " ");
 
-    vformat[i] = strcat(vformat[i], " ");
+    // remove trailing blank on last column's format
+    if (i == nfield-1) vformat[i][strlen(vformat[i])-1] = '\0';
+
+    ++i;
   }
 
   // setup boundary string
@@ -299,26 +287,22 @@ void DumpCustomMPIIO::init_style()
   // find current ptr for each compute,fix,variable
   // check that fix frequency is acceptable
 
-  int icompute;
-  for (int i = 0; i < ncompute; i++) {
-    icompute = modify->find_compute(id_compute[i]);
-    if (icompute < 0) error->all(FLERR, "Could not find dump custom compute ID");
-    compute[i] = modify->compute[icompute];
+  for (i = 0; i < ncompute; i++) {
+    compute[i] = modify->get_compute_by_id(id_compute[i]);
+    if (!compute[i]) error->all(FLERR,"Could not find dump custom compute ID {}",id_compute[i]);
   }
 
-  int ifix;
-  for (int i = 0; i < nfix; i++) {
-    ifix = modify->find_fix(id_fix[i]);
-    if (ifix < 0) error->all(FLERR, "Could not find dump custom fix ID");
-    fix[i] = modify->fix[ifix];
-    if (nevery % modify->fix[ifix]->peratom_freq)
-      error->all(FLERR, "Dump custom and fix not computed at compatible times");
+  for (i = 0; i < nfix; i++) {
+    fix[i] = modify->get_fix_by_id(id_fix[i]);
+    if (!fix[i]) error->all(FLERR,"Could not find dump custom fix ID {}", id_fix[i]);
+    if (nevery % fix[i]->peratom_freq)
+      error->all(FLERR,"Dump custom and fix not computed at compatible times");
   }
 
-  int ivariable;
-  for (int i = 0; i < nvariable; i++) {
-    ivariable = input->variable->find(id_variable[i]);
-    if (ivariable < 0) error->all(FLERR, "Could not find dump custom variable name");
+  for (i = 0; i < nvariable; i++) {
+    int ivariable = input->variable->find(id_variable[i]);
+    if (ivariable < 0)
+      error->all(FLERR,"Could not find dump custom variable name {}", id_variable[i]);
     variable[i] = ivariable;
   }