diff --git a/src/MISC/fix_ttm.cpp b/src/MISC/fix_ttm.cpp
index e759e600c9..e79f7616d9 100644
--- a/src/MISC/fix_ttm.cpp
+++ b/src/MISC/fix_ttm.cpp
@@ -31,6 +31,7 @@
 #include "error.h"
 #include "utils.h"
 #include "fmt/format.h"
+#include "tokenizer.h"
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
@@ -41,11 +42,11 @@ using namespace FixConst;
 
 FixTTM::FixTTM(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg),
-  random(NULL), fp(NULL), fpr(NULL), nsum(NULL), nsum_all(NULL),
-  T_initial_set(NULL), gfactor1(NULL), gfactor2(NULL), ratio(NULL),
-  flangevin(NULL), T_electron(NULL), T_electron_old(NULL), sum_vsq(NULL),
-  sum_mass_vsq(NULL), sum_vsq_all(NULL), sum_mass_vsq_all(NULL),
-  net_energy_transfer(NULL), net_energy_transfer_all(NULL)
+  random(NULL), fp(NULL), nsum(NULL), nsum_all(NULL),
+  gfactor1(NULL), gfactor2(NULL), ratio(NULL), flangevin(NULL),
+  T_electron(NULL), T_electron_old(NULL), sum_vsq(NULL), sum_mass_vsq(NULL),
+  sum_vsq_all(NULL), sum_mass_vsq_all(NULL), net_energy_transfer(NULL),
+  net_energy_transfer_all(NULL)
 {
   if (narg < 15) error->all(FLERR,"Illegal fix ttm command");
 
@@ -67,14 +68,6 @@ FixTTM::FixTTM(LAMMPS *lmp, int narg, char **arg) :
   nxnodes = force->inumeric(FLERR,arg[10]);
   nynodes = force->inumeric(FLERR,arg[11]);
   nznodes = force->inumeric(FLERR,arg[12]);
-
-  if (comm->me == 0) {
-    fpr = fopen(arg[13],"r");
-    if (fpr == NULL)
-      error->all(FLERR,fmt::format("Cannot open input file {}: {}",
-                                   arg[13], utils::getsyserror()));
-  }
-
   nfileevery = force->inumeric(FLERR,arg[14]);
 
   if (nfileevery) {
@@ -115,12 +108,14 @@ FixTTM::FixTTM(LAMMPS *lmp, int narg, char **arg) :
   gfactor2 = new double[atom->ntypes+1];
 
   // allocate 3d grid variables
+  // check for allowed maxium number of total grid nodes
 
-  total_nnodes = nxnodes*nynodes*nznodes;
+  total_nnodes = (bigint)nxnodes * (bigint)nynodes * (bigint)nznodes;
+  if (total_nnodes > MAXSMALLINT)
+    error->all(FLERR,"Too many nodes in fix ttm");
 
   memory->create(nsum,nxnodes,nynodes,nznodes,"ttm:nsum");
   memory->create(nsum_all,nxnodes,nynodes,nznodes,"ttm:nsum_all");
-  memory->create(T_initial_set,nxnodes,nynodes,nznodes,"ttm:T_initial_set");
   memory->create(sum_vsq,nxnodes,nynodes,nznodes,"ttm:sum_vsq");
   memory->create(sum_mass_vsq,nxnodes,nynodes,nznodes,"ttm:sum_mass_vsq");
   memory->create(sum_vsq_all,nxnodes,nynodes,nznodes,"ttm:sum_vsq_all");
@@ -149,7 +144,7 @@ FixTTM::FixTTM(LAMMPS *lmp, int narg, char **arg) :
 
   // set initial electron temperatures from user input file
 
-  if (me == 0) read_initial_electron_temperatures();
+  if (comm->me == 0) read_initial_electron_temperatures(arg[13]);
   MPI_Bcast(&T_electron[0][0][0],total_nnodes,MPI_DOUBLE,0,world);
 }
 
@@ -157,7 +152,7 @@ FixTTM::FixTTM(LAMMPS *lmp, int narg, char **arg) :
 
 FixTTM::~FixTTM()
 {
-  if (nfileevery && me == 0) fclose(fp);
+  if (fp) fclose(fp);
 
   delete random;
 
@@ -166,7 +161,6 @@ FixTTM::~FixTTM()
 
   memory->destroy(nsum);
   memory->destroy(nsum_all);
-  memory->destroy(T_initial_set);
   memory->destroy(sum_vsq);
   memory->destroy(sum_mass_vsq);
   memory->destroy(sum_vsq_all);
@@ -221,9 +215,9 @@ void FixTTM::init()
 
 void FixTTM::setup(int vflag)
 {
-  if (strstr(update->integrate_style,"verlet"))
+  if (utils::strmatch(update->integrate_style,"^verlet")) {
     post_force_setup(vflag);
-  else {
+  } else {
     ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
     post_force_respa_setup(vflag,nlevels_respa-1,0);
     ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
@@ -329,27 +323,48 @@ void FixTTM::reset_dt()
    only called by proc 0
 ------------------------------------------------------------------------- */
 
-void FixTTM::read_initial_electron_temperatures()
+void FixTTM::read_initial_electron_temperatures(const char *filename)
 {
-  char line[MAXLINE];
+  int ***T_initial_set;
+  memory->create(T_initial_set,nxnodes,nynodes,nznodes,"ttm:T_initial_set");
+  memset(&T_initial_set[0][0][0],0,total_nnodes*sizeof(int));
 
-  for (int ixnode = 0; ixnode < nxnodes; ixnode++)
-    for (int iynode = 0; iynode < nynodes; iynode++)
-      for (int iznode = 0; iznode < nznodes; iznode++)
-        T_initial_set[ixnode][iynode][iznode] = 0;
+  std::string name = utils::get_potential_file_path(filename);
+  if (name.empty())
+    error->one(FLERR,fmt::format("Cannot open input file: {}",
+                                 filename));
+  FILE *fpr = fopen(name.c_str(),"r");
 
   // read initial electron temperature values from file
 
+  char line[MAXLINE];
   int ixnode,iynode,iznode;
   double T_tmp;
   while (1) {
     if (fgets(line,MAXLINE,fpr) == NULL) break;
-    sscanf(line,"%d %d %d %lg",&ixnode,&iynode,&iznode,&T_tmp);
+    ValueTokenizer values(line);
+    if (values.has_next()) ixnode = values.next_int();
+    if (values.has_next()) iynode = values.next_int();
+    if (values.has_next()) iznode = values.next_int();
+    if (values.has_next()) T_tmp  = values.next_double();
+    else error->one(FLERR,"Incorrect format in fix ttm input file");
+
+    // check correctness of input data
+
+    if ((ixnode < 0) || (ixnode >= nxnodes)
+        || (iynode < 0) || (iynode >= nynodes)
+        || (iznode < 0) || (iznode >= nznodes))
+      error->one(FLERR,"Fix ttm invalide node index in fix ttm input");
+
     if (T_tmp < 0.0)
       error->one(FLERR,"Fix ttm electron temperatures must be > 0.0");
+
     T_electron[ixnode][iynode][iznode] = T_tmp;
     T_initial_set[ixnode][iynode][iznode] = 1;
   }
+  fclose(fpr);
+
+  // check completeness of input data
 
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
@@ -357,9 +372,7 @@ void FixTTM::read_initial_electron_temperatures()
         if (T_initial_set[ixnode][iynode][iznode] == 0)
           error->one(FLERR,"Initial temperatures not all set in fix ttm");
 
-  // close file
-
-  fclose(fpr);
+  memory->destroy(T_initial_set);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -463,7 +476,7 @@ void FixTTM::end_of_step()
               (T_electron_old[ixnode][iynode][right_znode] +
                T_electron_old[ixnode][iynode][left_znode] -
                2*T_electron_old[ixnode][iynode][iznode])/dz/dz) -
-              (net_energy_transfer_all[ixnode][iynode][iznode])/del_vol);
+             (net_energy_transfer_all[ixnode][iynode][iznode])/del_vol);
         }
   }
 
@@ -514,7 +527,7 @@ void FixTTM::end_of_step()
     MPI_Allreduce(&sum_mass_vsq[0][0][0],&sum_mass_vsq_all[0][0][0],
                   total_nnodes,MPI_DOUBLE,MPI_SUM,world);
 
-    if (me == 0) {
+    if (comm->me == 0) {
       fmt::print(fp,"{}",update->ntimestep);
 
       double T_a;
@@ -525,15 +538,15 @@ void FixTTM::end_of_step()
             if (nsum_all[ixnode][iynode][iznode] > 0)
               T_a = sum_mass_vsq_all[ixnode][iynode][iznode]/
                 (3.0*force->boltz*nsum_all[ixnode][iynode][iznode]/force->mvv2e);
-            fprintf(fp," %f",T_a);
+            fmt::print(fp," {}",T_a);
           }
 
-      fprintf(fp,"\t");
+      fputs("\t",fp);
       for (int ixnode = 0; ixnode < nxnodes; ixnode++)
         for (int iynode = 0; iynode < nynodes; iynode++)
           for (int iznode = 0; iznode < nznodes; iznode++)
-            fprintf(fp,"%f ",T_electron[ixnode][iynode][iznode]);
-      fprintf(fp,"\n");
+            fmt::print(fp," {}",T_electron[ixnode][iynode][iznode]);
+      fputs("\n",fp);
     }
   }
 }
@@ -560,7 +573,7 @@ void FixTTM::grow_arrays(int ngrow)
 }
 
 /* ----------------------------------------------------------------------
-  return the energy of the electronic subsystem or the net_energy transfer
+   return the energy of the electronic subsystem or the net_energy transfer
    between the subsystems
 ------------------------------------------------------------------------- */
 
@@ -582,7 +595,7 @@ double FixTTM::compute_vector(int n)
           electronic_density*del_vol;
         transfer_energy +=
           net_energy_transfer_all[ixnode][iynode][iznode]*update->dt;
-  }
+      }
 
   if (n == 0) return e_energy;
   if (n == 1) return transfer_energy;
diff --git a/src/MISC/fix_ttm.h b/src/MISC/fix_ttm.h
index 9fbae2a418..76631dbf57 100644
--- a/src/MISC/fix_ttm.h
+++ b/src/MISC/fix_ttm.h
@@ -48,17 +48,15 @@ class FixTTM : public Fix {
   double compute_vector(int);
 
  private:
-  int me;
   int nfileevery;
   int nlevels_respa;
   int seed;
   class RanMars *random;
-  FILE *fp,*fpr;
-  int nxnodes,nynodes,nznodes,total_nnodes;
-  int ***nsum;
-  int ***nsum_all,***T_initial_set;
-  double *gfactor1,*gfactor2,*ratio;
-  double **flangevin;
+  FILE *fp;
+  int nxnodes,nynodes,nznodes;
+  bigint total_nnodes;
+  int ***nsum, ***nsum_all;
+  double *gfactor1,*gfactor2,*ratio,**flangevin;
   double ***T_electron,***T_electron_old;
   double ***sum_vsq,***sum_mass_vsq;
   double ***sum_vsq_all,***sum_mass_vsq_all;
@@ -67,7 +65,7 @@ class FixTTM : public Fix {
   double electronic_thermal_conductivity;
   double gamma_p,gamma_s,v_0,v_0_sq;
 
-  void read_initial_electron_temperatures();
+  void read_initial_electron_temperatures(const char *);
 };
 
 }
diff --git a/src/USER-MISC/fix_ttm_mod.cpp b/src/USER-MISC/fix_ttm_mod.cpp
index 9051414d07..cd3fbaa721 100644
--- a/src/USER-MISC/fix_ttm_mod.cpp
+++ b/src/USER-MISC/fix_ttm_mod.cpp
@@ -34,6 +34,7 @@
 #include "math_const.h"
 #include "utils.h"
 #include "fmt/format.h"
+#include "tokenizer.h"
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
@@ -65,7 +66,12 @@ static const char cite_fix_ttm_mod[] =
 /* ---------------------------------------------------------------------- */
 
 FixTTMMod::FixTTMMod(LAMMPS *lmp, int narg, char **arg) :
-  Fix(lmp, narg, arg)
+  Fix(lmp, narg, arg),
+  random(NULL), fp(NULL), nsum(NULL), nsum_all(NULL),
+  gfactor1(NULL), gfactor2(NULL), ratio(NULL), flangevin(NULL),
+  T_electron(NULL), T_electron_old(NULL), sum_vsq(NULL), sum_mass_vsq(NULL),
+  sum_vsq_all(NULL), sum_mass_vsq_all(NULL), net_energy_transfer(NULL),
+  net_energy_transfer_all(NULL)
 {
   if (lmp->citeme) lmp->citeme->add(cite_fix_ttm_mod);
 
@@ -82,32 +88,20 @@ FixTTMMod::FixTTMMod(LAMMPS *lmp, int narg, char **arg) :
   if (seed <= 0)
     error->all(FLERR,"Invalid random number seed in fix ttm/mod command");
 
-  FILE *fpr_2 = force->open_potential(arg[4]);
-  if (fpr_2 == NULL) {
-    char str[128];
-    snprintf(str,128,"Cannot open file %s",arg[4]);
-    error->all(FLERR,str);
-  }
-
   nxnodes = force->inumeric(FLERR,arg[5]);
   nynodes = force->inumeric(FLERR,arg[6]);
   nznodes = force->inumeric(FLERR,arg[7]);
   if (nxnodes <= 0 || nynodes <= 0 || nznodes <= 0)
     error->all(FLERR,"Fix ttm/mod number of nodes must be > 0");
 
-  const char *filename = arg[8];
-  FILE *fpr = force->open_potential(filename);
-  if (fpr == NULL) {
-    char str[128];
-    snprintf(str,128,"Cannot open file %s",filename);
-    error->all(FLERR,str);
-  }
+  total_nnodes = (bigint)nxnodes * (bigint)nynodes * (bigint)nznodes;
+  if (total_nnodes > MAXSMALLINT)
+    error->all(FLERR,"Too many nodes in fix ttm/mod");
 
   nfileevery = force->inumeric(FLERR,arg[9]);
   if (nfileevery > 0) {
     if (narg != 11) error->all(FLERR,"Illegal fix ttm/mod command");
-    MPI_Comm_rank(world,&me);
-    if (me == 0) {
+    if (comm->me == 0) {
       fp = fopen(arg[10],"w");
       if (fp == NULL) {
         char str[128];
@@ -116,121 +110,11 @@ FixTTMMod::FixTTMMod(LAMMPS *lmp, int narg, char **arg) :
       }
     }
   }
-  char linee[MAXLINE];
-  double tresh_d;
-  int tresh_i;
-  // C0 (metal)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  esheat_0 = tresh_d;
-  // C1 (metal*10^3)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  esheat_1 = tresh_d;
-  // C2 (metal*10^6)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  esheat_2 = tresh_d;
-  // C3 (metal*10^9)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  esheat_3 = tresh_d;
-  // C4 (metal*10^12)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  esheat_4 = tresh_d;
-  // C_limit
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  C_limit = tresh_d;
-  //Temperature damping factor
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  T_damp = tresh_d;
-  // rho_e
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  electronic_density = tresh_d;
-  //thermal_diffusion
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  el_th_diff = tresh_d;
-  // gamma_p
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  gamma_p = tresh_d;
-  // gamma_s
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  gamma_s = tresh_d;
-  // v0
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  v_0 = tresh_d;
-  // average intensity of pulse (source of energy) (metal units)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  intensity = tresh_d;
-  // coordinate of 1st surface in x-direction (in box units) - constant
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%d",&tresh_i);
-  surface_l = tresh_i;
-  // coordinate of 2nd surface in x-direction (in box units) - constant
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%d",&tresh_i);
-  surface_r = tresh_i;
-  // skin_layer = intensity is reduced (I=I0*exp[-x/skin_layer])
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%d",&tresh_i);
-  skin_layer = tresh_i;
-  // width of pulse (picoseconds)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  width = tresh_d;
-  // factor of electronic pressure (PF) Pe = PF*Ce*Te
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  pres_factor = tresh_d;
-  // effective free path of electrons (angstrom)
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  free_path = tresh_d;
-  // ionic density (ions*angstrom^{-3})
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  ionic_density = tresh_d;
-  // if movsur = 0: surface is freezed
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%d",&tresh_i);
-  movsur = tresh_i;
-  // electron_temperature_min
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  utils::sfgets(FLERR,linee,MAXLINE,fpr_2,filename,error);
-  sscanf(linee,"%lg",&tresh_d);
-  electron_temperature_min = tresh_d;
-  fclose(fpr_2);
-  //t_surface is determined by electronic temperature (not constant)
+
+  read_parameters(arg[4]);
+
+  // t_surface is determined by electronic temperature (not constant)
+
   t_surface_l = surface_l;
   mult_factor = intensity;
   duration = 0.0;
@@ -255,7 +139,6 @@ FixTTMMod::FixTTMMod(LAMMPS *lmp, int narg, char **arg) :
   total_nnodes = nxnodes*nynodes*nznodes;
   memory->create(nsum,nxnodes,nynodes,nznodes,"ttm/mod:nsum");
   memory->create(nsum_all,nxnodes,nynodes,nznodes,"ttm/mod:nsum_all");
-  memory->create(T_initial_set,nxnodes,nynodes,nznodes,"ttm/mod:T_initial_set");
   memory->create(sum_vsq,nxnodes,nynodes,nznodes,"ttm/mod:sum_vsq");
   memory->create(sum_mass_vsq,nxnodes,nynodes,nznodes,"ttm/mod:sum_mass_vsq");
   memory->create(sum_vsq_all,nxnodes,nynodes,nznodes,"ttm/mod:sum_vsq_all");
@@ -270,31 +153,36 @@ FixTTMMod::FixTTMMod(LAMMPS *lmp, int narg, char **arg) :
                  "ttm/mod:net_energy_transfer_all");
   flangevin = NULL;
   grow_arrays(atom->nmax);
+
   // zero out the flangevin array
+
   for (int i = 0; i < atom->nmax; i++) {
     flangevin[i][0] = 0;
     flangevin[i][1] = 0;
     flangevin[i][2] = 0;
   }
+
   atom->add_callback(0);
   atom->add_callback(1);
+
   // set initial electron temperatures from user input file
-  if (me == 0) read_initial_electron_temperatures(fpr);
+
+  if (comm->me == 0) read_initial_electron_temperatures(arg[8]);
   MPI_Bcast(&T_electron[0][0][0],total_nnodes,MPI_DOUBLE,0,world);
-  fclose(fpr);
 }
 
 /* ---------------------------------------------------------------------- */
 
 FixTTMMod::~FixTTMMod()
 {
-  if (nfileevery && me == 0) fclose(fp);
+  if (fp) fclose(fp);
   delete random;
+
   delete [] gfactor1;
   delete [] gfactor2;
+
   memory->destroy(nsum);
   memory->destroy(nsum_all);
-  memory->destroy(T_initial_set);
   memory->destroy(sum_vsq);
   memory->destroy(sum_mass_vsq);
   memory->destroy(sum_vsq_all);
@@ -328,16 +216,20 @@ void FixTTMMod::init()
     error->all(FLERR,"Cannot use non-periodic boundares with fix ttm/mod");
   if (domain->triclinic)
     error->all(FLERR,"Cannot use fix ttm/mod with triclinic box");
+
   // set force prefactors
+
   for (int i = 1; i <= atom->ntypes; i++) {
     gfactor1[i] = - gamma_p / force->ftm2v;
     gfactor2[i] =
       sqrt(24.0*force->boltz*gamma_p/update->dt/force->mvv2e) / force->ftm2v;
   }
+
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++)
         net_energy_transfer_all[ixnode][iynode][iznode] = 0;
+
   if (strstr(update->integrate_style,"respa"))
     nlevels_respa = ((Respa *) update->integrate)->nlevels;
 }
@@ -346,7 +238,7 @@ void FixTTMMod::init()
 
 void FixTTMMod::setup(int vflag)
 {
-  if (strstr(update->integrate_style,"verlet")) {
+  if (utils::strmatch(update->integrate_style,"^verlet")) {
     post_force_setup(vflag);
   } else {
     ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
@@ -365,13 +257,17 @@ void FixTTMMod::post_force(int /*vflag*/)
   int *type = atom->type;
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
+
   double dx = domain->xprd/nxnodes;
   double dy = domain->yprd/nynodes;
   double dz = domain->zprd/nynodes;
   double gamma1,gamma2;
+
   // apply damping and thermostat to all atoms in fix group
+
   for (int i = 0; i < nlocal; i++) {
     if (mask[i] & groupbit) {
+
       double xscale = (x[i][0] - domain->boxlo[0])/domain->xprd;
       double yscale = (x[i][1] - domain->boxlo[1])/domain->yprd;
       double zscale = (x[i][2] - domain->boxlo[2])/domain->zprd;
@@ -384,9 +280,12 @@ void FixTTMMod::post_force(int /*vflag*/)
       while (ixnode < 0) ixnode += nxnodes;
       while (iynode < 0) iynode += nynodes;
       while (iznode < 0) iznode += nznodes;
+
       if (T_electron[ixnode][iynode][iznode] < 0)
         error->all(FLERR,"Electronic temperature dropped below zero");
+
       double tsqrt = sqrt(T_electron[ixnode][iynode][iznode]);
+
       gamma1 = gfactor1[type[i]];
       double vsq = v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2];
       if (vsq > v_0_sq) gamma1 *= (gamma_p + gamma_s)/gamma_p;
@@ -455,7 +354,9 @@ void FixTTMMod::post_force_setup(int /*vflag*/)
   double **f = atom->f;
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
+
   // apply langevin forces that have been stored from previous run
+
   for (int i = 0; i < nlocal; i++) {
     if (mask[i] & groupbit) {
       f[i][0] += flangevin[i][0];
@@ -488,33 +389,209 @@ void FixTTMMod::reset_dt()
       sqrt(24.0*force->boltz*gamma_p/update->dt/force->mvv2e) / force->ftm2v;
 }
 
+/* ----------------------------------------------------------------------
+   read in ttm/mod parameters from a user-specified file
+   only called by proc 0
+------------------------------------------------------------------------- */
+
+void FixTTMMod::read_parameters(const char *filename)
+{
+  char line[MAXLINE];
+  std::string name = utils::get_potential_file_path(filename);
+  if (name.empty())
+    error->one(FLERR,fmt::format("Cannot open input file: {}",
+                                 filename));
+  FILE *fpr = fopen(name.c_str(),"r");
+
+  // C0 (metal)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  esheat_0 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // C1 (metal*10^3)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  esheat_1 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // C2 (metal*10^6)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  esheat_2 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // C3 (metal*10^9)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  esheat_3 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // C4 (metal*10^12)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  esheat_4 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // C_limit
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  C_limit = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // Temperature damping factor
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  T_damp = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // rho_e
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  electronic_density = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // thermal_diffusion
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  el_th_diff = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // gamma_p
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  gamma_p = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // gamma_s
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  gamma_s = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // v0
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  v_0 = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // average intensity of pulse (source of energy) (metal units)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  intensity = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // coordinate of 1st surface in x-direction (in box units) - constant
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  surface_l = utils::inumeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // coordinate of 2nd surface in x-direction (in box units) - constant
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  surface_r = utils::inumeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // skin_layer = intensity is reduced (I=I0*exp[-x/skin_layer])
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  skin_layer = utils::inumeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // width of pulse (picoseconds)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  width = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // factor of electronic pressure (PF) Pe = PF*Ce*Te
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  pres_factor = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // effective free path of electrons (angstrom)
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  free_path = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // ionic density (ions*angstrom^{-3})
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  ionic_density = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // if movsur = 0: surface is frozen
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  movsur = utils::inumeric(FLERR,utils::trim(line).c_str(),true,lmp);
+
+  // electron_temperature_min
+
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  utils::sfgets(FLERR,line,MAXLINE,fpr,filename,error);
+  electron_temperature_min = utils::numeric(FLERR,utils::trim(line).c_str(),true,lmp);
+  fclose(fpr);
+}
+
 /* ----------------------------------------------------------------------
    read in initial electron temperatures from a user-specified file
    only called by proc 0
 ------------------------------------------------------------------------- */
 
-void FixTTMMod::read_initial_electron_temperatures(FILE *fpr)
+void FixTTMMod::read_initial_electron_temperatures(const char *filename)
 {
-  char line[MAXLINE];
-  for (int ixnode = 0; ixnode < nxnodes; ixnode++)
-    for (int iynode = 0; iynode < nynodes; iynode++)
-      for (int iznode = 0; iznode < nznodes; iznode++)
-        T_initial_set[ixnode][iynode][iznode] = 0;
+  int ***T_initial_set;
+  memory->create(T_initial_set,nxnodes,nynodes,nznodes,"ttm/mod:T_initial_set");
+  memset(&T_initial_set[0][0][0],0,total_nnodes*sizeof(int));
+
+  std::string name = utils::get_potential_file_path(filename);
+  if (name.empty())
+    error->one(FLERR,fmt::format("Cannot open input file: {}",
+                                 filename));
+  FILE *fpr = fopen(name.c_str(),"r");
+
   // read initial electron temperature values from file
+
+  char line[MAXLINE];
   int ixnode,iynode,iznode;
   double T_tmp;
   while (1) {
     if (fgets(line,MAXLINE,fpr) == NULL) break;
-    sscanf(line,"%d %d %d %lg",&ixnode,&iynode,&iznode,&T_tmp);
-    if (T_tmp < 0.0) error->one(FLERR,"Fix ttm/mod electron temperatures must be >= 0.0");
+    ValueTokenizer values(line);
+    if (values.has_next()) ixnode = values.next_int();
+    if (values.has_next()) iynode = values.next_int();
+    if (values.has_next()) iznode = values.next_int();
+    if (values.has_next()) T_tmp  = values.next_double();
+    else error->one(FLERR,"Incorrect format in fix ttm input file");
+
+    // check correctness of input data
+
+    if ((ixnode < 0) || (ixnode >= nxnodes)
+        || (iynode < 0) || (iynode >= nynodes)
+        || (iznode < 0) || (iznode >= nznodes))
+      error->one(FLERR,"Fix ttm invalide node index in fix ttm input");
+
+    if (T_tmp < 0.0)
+      error->one(FLERR,"Fix ttm electron temperatures must be > 0.0");
+
     T_electron[ixnode][iynode][iznode] = T_tmp;
     T_initial_set[ixnode][iynode][iznode] = 1;
   }
+  fclose(fpr);
+
+  // check completeness of input data
+
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++)
         if (T_initial_set[ixnode][iynode][iznode] == 0)
-          error->one(FLERR,"Initial temperatures not all set in fix ttm/mod");
+          error->one(FLERR,"Initial temperatures not all set in fix ttm");
+
+  memory->destroy(T_initial_set);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -551,6 +628,7 @@ void FixTTMMod::end_of_step()
   int *type = atom->type;
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
+
   if (movsur == 1){
     for (int ixnode = 0; ixnode < nxnodes; ixnode++)
       for (int iynode = 0; iynode < nynodes; iynode++)
@@ -566,6 +644,7 @@ void FixTTMMod::end_of_step()
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++)
         net_energy_transfer[ixnode][iynode][iznode] = 0;
+
   for (int i = 0; i < nlocal; i++)
     if (mask[i] & groupbit) {
       double xscale = (x[i][0] - domain->boxlo[0])/domain->xprd;
@@ -587,9 +666,11 @@ void FixTTMMod::end_of_step()
              flangevin[i][2]*v[i][2]);
       }
     }
+
   MPI_Allreduce(&net_energy_transfer[0][0][0],
                 &net_energy_transfer_all[0][0][0],
                 total_nnodes,MPI_DOUBLE,MPI_SUM,world);
+
   double dx = domain->xprd/nxnodes;
   double dy = domain->yprd/nynodes;
   double dz = domain->zprd/nznodes;
@@ -611,6 +692,7 @@ void FixTTMMod::end_of_step()
         }
   // num_inner_timesteps = # of inner steps (thermal solves)
   // required this MD step to maintain a stable explicit solve
+
   int num_inner_timesteps = 1;
   double inner_dt = update->dt;
   double stability_criterion = 0.0;
@@ -720,9 +802,13 @@ void FixTTMMod::end_of_step()
       (el_thermal_conductivity*(1.0/dx/dx + 1.0/dy/dy + 1.0/dz/dz));
 
   } while (stability_criterion < 0.0);
+
   // output nodal temperatures for current timestep
+
   if ((nfileevery) && !(update->ntimestep % nfileevery)) {
+
     // compute atomic Ta for each grid point
+
     for (int ixnode = 0; ixnode < nxnodes; ixnode++)
       for (int iynode = 0; iynode < nynodes; iynode++)
         for (int iznode = 0; iznode < nznodes; iznode++) {
@@ -733,6 +819,7 @@ void FixTTMMod::end_of_step()
           sum_vsq_all[ixnode][iynode][iznode] = 0.0;
           sum_mass_vsq_all[ixnode][iynode][iznode] = 0.0;
         }
+
     double massone;
     for (int i = 0; i < nlocal; i++)
       if (mask[i] & groupbit) {
@@ -755,36 +842,39 @@ void FixTTMMod::end_of_step()
         sum_vsq[ixnode][iynode][iznode] += vsq;
         sum_mass_vsq[ixnode][iynode][iznode] += massone*vsq;
       }
+
     MPI_Allreduce(&nsum[0][0][0],&nsum_all[0][0][0],total_nnodes,
                   MPI_INT,MPI_SUM,world);
     MPI_Allreduce(&sum_vsq[0][0][0],&sum_vsq_all[0][0][0],total_nnodes,
                   MPI_DOUBLE,MPI_SUM,world);
     MPI_Allreduce(&sum_mass_vsq[0][0][0],&sum_mass_vsq_all[0][0][0],
                   total_nnodes,MPI_DOUBLE,MPI_SUM,world);
-    MPI_Allreduce(&t_surface_l,&surface_l,
-                  1,MPI_INT,MPI_MIN,world);
-    if (me == 0) {
+    MPI_Allreduce(&t_surface_l,&surface_l,1,MPI_INT,MPI_MIN,world);
+
+    if (comm->me == 0) {
       fmt::print(fp,"{}",update->ntimestep);
+
       double T_a;
       for (int ixnode = 0; ixnode < nxnodes; ixnode++)
         for (int iynode = 0; iynode < nynodes; iynode++)
           for (int iznode = 0; iznode < nznodes; iznode++) {
             T_a = 0;
-            if (nsum_all[ixnode][iynode][iznode] > 0){
+            if (nsum_all[ixnode][iynode][iznode] > 0) {
               T_a = sum_mass_vsq_all[ixnode][iynode][iznode]/
                 (3.0*force->boltz*nsum_all[ixnode][iynode][iznode]/force->mvv2e);
               if (movsur == 1){
                 if (T_electron[ixnode][iynode][iznode]==0.0) T_electron[ixnode][iynode][iznode] = electron_temperature_min;
               }
             }
-            fprintf(fp," %f",T_a);
+            fmt::print(fp," {}",T_a);
           }
-      fprintf(fp,"\t");
+
+      fputs("\t",fp);
       for (int ixnode = 0; ixnode < nxnodes; ixnode++)
         for (int iynode = 0; iynode < nynodes; iynode++)
           for (int iznode = 0; iznode < nznodes; iznode++)
-            fprintf(fp,"%f ",T_electron[ixnode][iynode][iznode]);
-      fprintf(fp,"\n");
+            fmt::print(fp," {}",T_electron[ixnode][iynode][iznode]);
+      fputs("\n",fp);
     }
   }
 }
@@ -817,10 +907,12 @@ double FixTTMMod::compute_vector(int n)
 {
   double e_energy = 0.0;
   double transfer_energy = 0.0;
+
   double dx = domain->xprd/nxnodes;
   double dy = domain->yprd/nynodes;
   double dz = domain->zprd/nznodes;
   double del_vol = dx*dy*dz;
+
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++) {
@@ -828,6 +920,7 @@ double FixTTMMod::compute_vector(int n)
         transfer_energy +=
           net_energy_transfer_all[ixnode][iynode][iznode]*update->dt;
       }
+
   if (n == 0) return e_energy;
   if (n == 1) return transfer_energy;
   return 0.0;
@@ -841,17 +934,21 @@ void FixTTMMod::write_restart(FILE *fp)
 {
   double *rlist;
   memory->create(rlist,nxnodes*nynodes*nznodes+1,"ttm/mod:rlist");
+
   int n = 0;
   rlist[n++] = seed;
+
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++)
-        rlist[n++] = T_electron[ixnode][iynode][iznode];
+        rlist[n++] =  T_electron[ixnode][iynode][iznode];
+
   if (comm->me == 0) {
     int size = n * sizeof(double);
     fwrite(&size,sizeof(int),1,fp);
     fwrite(rlist,sizeof(double),n,fp);
   }
+
   memory->destroy(rlist);
 }
 
@@ -863,12 +960,16 @@ void FixTTMMod::restart(char *buf)
 {
   int n = 0;
   double *rlist = (double *) buf;
+
   // the seed must be changed from the initial seed
+
   seed = static_cast<int> (0.5*rlist[n++]);
+
   for (int ixnode = 0; ixnode < nxnodes; ixnode++)
     for (int iynode = 0; iynode < nynodes; iynode++)
       for (int iznode = 0; iznode < nznodes; iznode++)
         T_electron[ixnode][iynode][iznode] = rlist[n++];
+
   delete random;
   random = new RanMars(lmp,seed+comm->me);
 }
@@ -893,10 +994,13 @@ int FixTTMMod::pack_restart(int i, double *buf)
 void FixTTMMod::unpack_restart(int nlocal, int nth)
 {
   double **extra = atom->extra;
+
   // skip to Nth set of extra values
+
   int m = 0;
   for (int i = 0; i < nth; i++) m += static_cast<int> (extra[nlocal][m]);
   m++;
+
   flangevin[nlocal][0] = extra[nlocal][m++];
   flangevin[nlocal][1] = extra[nlocal][m++];
   flangevin[nlocal][2] = extra[nlocal][m++];
diff --git a/src/USER-MISC/fix_ttm_mod.h b/src/USER-MISC/fix_ttm_mod.h
index 21f6e57e04..84d976ec07 100644
--- a/src/USER-MISC/fix_ttm_mod.h
+++ b/src/USER-MISC/fix_ttm_mod.h
@@ -53,17 +53,15 @@ class FixTTMMod : public Fix {
   double compute_vector(int);
 
  private:
-  int me;
   int nfileevery;
   int nlevels_respa;
   int seed;
   class RanMars *random;
   FILE *fp;
-  int nxnodes,nynodes,nznodes,total_nnodes;
-  int ***nsum;
-  int ***nsum_all,***T_initial_set;
-  double *gfactor1,*gfactor2,*ratio;
-  double **flangevin;
+  int nxnodes,nynodes,nznodes;
+  bigint total_nnodes;
+  int ***nsum, ***nsum_all;
+  double *gfactor1,*gfactor2,*ratio,**flangevin;
   double ***T_electron,***T_electron_old,***T_electron_first;
   double ***sum_vsq,***sum_mass_vsq;
   double ***sum_vsq_all,***sum_mass_vsq_all;
@@ -79,7 +77,8 @@ class FixTTMMod : public Fix {
   double electron_temperature_min;
   el_heat_capacity_thermal_conductivity el_properties(double);
   double el_sp_heat_integral(double);
-  void read_initial_electron_temperatures(FILE *);
+  void read_parameters(const char *);
+  void read_initial_electron_temperatures(const char *);
 };
 
 }
diff --git a/src/utils.cpp b/src/utils.cpp
index 4efa35a8d1..ce6a64f22f 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -348,6 +348,19 @@ tagint utils::tnumeric(const char *file, int line, const char *str,
   return ATOTAGINT(str);
 }
 
+/* ----------------------------------------------------------------------
+   Return string without leading or trailing whitespace
+------------------------------------------------------------------------- */
+
+std::string utils::trim(const std::string & line) {
+  int beg = re_match(line.c_str(),"\\S+");
+  int end = re_match(line.c_str(),"\\s+$");
+  if (beg < 0) beg = 0;
+  if (end < 0) end = line.size();
+
+  return line.substr(beg,end-beg);
+}
+
 /* ----------------------------------------------------------------------
    Return string without trailing # comment
 ------------------------------------------------------------------------- */
diff --git a/src/utils.h b/src/utils.h
index abaa87ca5f..3919f8d4d5 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -143,6 +143,13 @@ namespace LAMMPS_NS {
     tagint tnumeric(const char *file, int line, const char *str,
                     bool do_abort, LAMMPS *lmp);
 
+    /**
+     * \brief Trim leading and trailing whitespace. Like TRIM() in Fortran.
+     * \param line string that should be trimmed
+     * \return new string without whitespace (string)
+     */
+    std::string trim(const std::string &line);
+
     /**
      * \brief Trim anything from '#' onward
      * \param line string that should be trimmed
diff --git a/unittest/utils/test_utils.cpp b/unittest/utils/test_utils.cpp
index 22a647f460..08aa5df1ff 100644
--- a/unittest/utils/test_utils.cpp
+++ b/unittest/utils/test_utils.cpp
@@ -25,6 +25,24 @@ using ::testing::EndsWith;
 using ::testing::Eq;
 using ::testing::StrEq;
 
+TEST(Utils, trim)
+{
+    auto trimmed = utils::trim("\t some text");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("some text \r\n");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("\v some text \f");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("   some\t text    ");
+    ASSERT_THAT(trimmed, StrEq("some\t text"));
+
+    trimmed = utils::trim("  \t\n   ");
+    ASSERT_THAT(trimmed, StrEq(""));
+}
+
 TEST(Utils, trim_comment)
 {
     auto trimmed = utils::trim_comment("some text # comment");