diff --git a/src/read_dump.cpp b/src/read_dump.cpp
index 82f5c969df..3002eaffc3 100644
--- a/src/read_dump.cpp
+++ b/src/read_dump.cpp
@@ -1217,27 +1217,19 @@ int ReadDump::fields_and_keywords(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"box") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) boxflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) boxflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      boxflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"replace") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) replaceflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) replaceflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      replaceflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"purge") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) purgeflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) purgeflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      purgeflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"trim") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) trimflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) trimflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      trimflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"add") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
@@ -1257,15 +1249,11 @@ int ReadDump::fields_and_keywords(int narg, char **arg)
       iarg += 3;
     } else if (strcmp(arg[iarg],"scaled") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) scaleflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) scaleflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      scaleflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"wrapped") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
-      if (strcmp(arg[iarg+1],"yes") == 0) wrapflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) wrapflag = 0;
-      else error->all(FLERR,"Illegal read_dump command");
+      wrapflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"format") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal read_dump command");
diff --git a/src/rerun.cpp b/src/rerun.cpp
index f9bb507a11..ce21fbc2b8 100644
--- a/src/rerun.cpp
+++ b/src/rerun.cpp
@@ -106,11 +106,7 @@ void Rerun::command(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"post") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal rerun command");
-      if (strcmp(arg[iarg+1],"yes") == 0) {
-        postflag = 1;
-      } else if (strcmp(arg[iarg+1],"no") == 0) {
-        postflag = 0;
-      } else error->all(FLERR,"Illegal rerun command");
+      postflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"dump") == 0) {
       break;
diff --git a/src/reset_atom_ids.cpp b/src/reset_atom_ids.cpp
index 3aea800b6f..822490ffc8 100644
--- a/src/reset_atom_ids.cpp
+++ b/src/reset_atom_ids.cpp
@@ -69,9 +69,7 @@ void ResetIDs::command(int narg, char **arg)
   while (iarg < narg) {
     if (strcmp(arg[iarg],"sort") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal reset_atom_ids command");
-      if (strcmp(arg[iarg+1],"yes") == 0) sortflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) sortflag = 0;
-      else error->all(FLERR,"Illegal reset_atom_ids command");
+      sortflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else error->all(FLERR,"Illegal reset_atom_ids command");
   }
diff --git a/src/reset_mol_ids.cpp b/src/reset_mol_ids.cpp
index cf5bcdec6e..ff3602a745 100644
--- a/src/reset_mol_ids.cpp
+++ b/src/reset_mol_ids.cpp
@@ -77,15 +77,11 @@ void ResetMolIDs::command(int narg, char **arg)
   while (iarg < narg) {
     if (strcmp(arg[iarg],"compress") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal reset_mol_ids command");
-      if (strcmp(arg[iarg+1],"yes") == 0) compressflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) compressflag = 0;
-      else error->all(FLERR,"Illegal reset_mol_ids command");
+      compressflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"single") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal reset_mol_ids command");
-      if (strcmp(arg[iarg+1],"yes") == 0) singleflag = 1;
-      else if (strcmp(arg[iarg+1],"no") == 0) singleflag = 0;
-      else error->all(FLERR,"Illegal reset_mol_ids command");
+      singleflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"offset") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal reset_mol_ids command");
diff --git a/src/run.cpp b/src/run.cpp
index 2d8b4816a4..a026580c83 100644
--- a/src/run.cpp
+++ b/src/run.cpp
@@ -77,15 +77,11 @@ void Run::command(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"pre") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal run command");
-      if (strcmp(arg[iarg+1],"no") == 0) preflag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) preflag = 1;
-      else error->all(FLERR,"Illegal run command");
+      preflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"post") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal run command");
-      if (strcmp(arg[iarg+1],"no") == 0) postflag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) postflag = 1;
-      else error->all(FLERR,"Illegal run command");
+      postflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
 
       // all remaining args are commands
diff --git a/src/thermo.cpp b/src/thermo.cpp
index eaf208c2eb..434012870b 100644
--- a/src/thermo.cpp
+++ b/src/thermo.cpp
@@ -556,16 +556,12 @@ void Thermo::modify_params(int narg, char **arg)
     } else if (strcmp(arg[iarg],"norm") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal thermo_modify command");
       normuserflag = 1;
-      if (strcmp(arg[iarg+1],"no") == 0) normuser = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) normuser = 1;
-      else error->all(FLERR,"Illegal thermo_modify command");
+      normuser = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
 
     } else if (strcmp(arg[iarg],"flush") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal thermo_modify command");
-      if (strcmp(arg[iarg+1],"no") == 0) flushflag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) flushflag = 1;
-      else error->all(FLERR,"Illegal thermo_modify command");
+      flushflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
 
     } else if (strcmp(arg[iarg],"line") == 0) {
diff --git a/src/velocity.cpp b/src/velocity.cpp
index fa09f451df..c151691b38 100644
--- a/src/velocity.cpp
+++ b/src/velocity.cpp
@@ -36,6 +36,7 @@ using namespace LAMMPS_NS;
 
 enum{CREATE,SET,SCALE,RAMP,ZERO};
 enum{ALL,LOCAL,GEOM};
+enum{UNIFORM,GAUSSIAN};
 enum{NONE,CONSTANT,EQUAL,ATOM};
 
 #define WARMUP 100
@@ -84,7 +85,7 @@ void Velocity::command(int narg, char **arg)
   // set defaults
 
   temperature = nullptr;
-  dist_flag = 0;
+  dist_flag = UNIFORM;
   sum_flag = 0;
   momentum_flag = 1;
   rotation_flag = 0;
@@ -149,11 +150,12 @@ void Velocity::init_external(const char *extgroup)
   groupbit = group->bitmask[igroup];
 
   temperature = nullptr;
-  dist_flag = 0;
+  dist_flag = UNIFORM;
   sum_flag = 0;
   momentum_flag = 1;
   rotation_flag = 0;
   loop_flag = ALL;
+  rfix = -1;
   scale_flag = 1;
   bias_flag = 0;
 }
@@ -275,11 +277,11 @@ void Velocity::create(double t_desired, int seed)
     int natoms = static_cast<int> (atom->natoms);
 
     for (i = 1; i <= natoms; i++) {
-      if (dist_flag == 0) {
+      if (dist_flag == UNIFORM) {
         vx = random->uniform() - 0.5;
         vy = random->uniform() - 0.5;
         vz = random->uniform() - 0.5;
-      } else {
+      } else { // GAUSSIAN
         vx = random->gaussian();
         vy = random->gaussian();
         vz = random->gaussian();
@@ -310,11 +312,11 @@ void Velocity::create(double t_desired, int seed)
 
     for (i = 0; i < nlocal; i++) {
       if (mask[i] & groupbit) {
-        if (dist_flag == 0) {
+        if (dist_flag == UNIFORM) {
           vx = random->uniform() - 0.5;
           vy = random->uniform() - 0.5;
           vz = random->uniform() - 0.5;
-        } else {
+        } else { // GAUSSIAN
           vx = random->gaussian();
           vy = random->gaussian();
           vz = random->gaussian();
@@ -335,11 +337,11 @@ void Velocity::create(double t_desired, int seed)
     for (i = 0; i < nlocal; i++) {
       if (mask[i] & groupbit) {
         random->reset(seed,x[i]);
-        if (dist_flag == 0) {
+        if (dist_flag == UNIFORM) {
           vx = random->uniform() - 0.5;
           vy = random->uniform() - 0.5;
           vz = random->uniform() - 0.5;
-        } else {
+        } else { // GAUSSIAN
           vx = random->gaussian();
           vy = random->gaussian();
           vz = random->gaussian();
@@ -824,27 +826,21 @@ void Velocity::options(int narg, char **arg)
   while (iarg < narg) {
     if (strcmp(arg[iarg],"dist") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
-      if (strcmp(arg[iarg+1],"uniform") == 0) dist_flag = 0;
-      else if (strcmp(arg[iarg+1],"gaussian") == 0) dist_flag = 1;
+      if (strcmp(arg[iarg+1],"uniform") == 0) dist_flag = UNIFORM;
+      else if (strcmp(arg[iarg+1],"gaussian") == 0) dist_flag = GAUSSIAN;
       else error->all(FLERR,"Illegal velocity command");
       iarg += 2;
     } else if (strcmp(arg[iarg],"sum") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
-      if (strcmp(arg[iarg+1],"no") == 0) sum_flag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) sum_flag = 1;
-      else error->all(FLERR,"Illegal velocity command");
+      sum_flag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"mom") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
-      if (strcmp(arg[iarg+1],"no") == 0) momentum_flag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) momentum_flag = 1;
-      else error->all(FLERR,"Illegal velocity command");
+      momentum_flag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"rot") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
-      if (strcmp(arg[iarg+1],"no") == 0) rotation_flag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) rotation_flag = 1;
-      else error->all(FLERR,"Illegal velocity command");
+      rotation_flag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"temp") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
@@ -856,9 +852,7 @@ void Velocity::options(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"bias") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");
-      if (strcmp(arg[iarg+1],"no") == 0) bias_flag = 0;
-      else if (strcmp(arg[iarg+1],"yes") == 0) bias_flag = 1;
-      else error->all(FLERR,"Illegal velocity command");
+      bias_flag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"loop") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal velocity command");