diff --git a/src/MISC/fix_ipi.cpp b/src/MISC/fix_ipi.cpp
index 277ddc8489..6fc3ec97b5 100644
--- a/src/MISC/fix_ipi.cpp
+++ b/src/MISC/fix_ipi.cpp
@@ -18,18 +18,19 @@
 
 #include "fix_ipi.h"
 
-#include <cstring>
 #include "atom.h"
-#include "force.h"
-#include "update.h"
+#include "comm.h"
+#include "compute.h"
+#include "domain.h"
 #include "error.h"
+#include "force.h"
+#include "irregular.h"
 #include "kspace.h"
 #include "modify.h"
-#include "compute.h"
-#include "comm.h"
 #include "neighbor.h"
-#include "irregular.h"
-#include "domain.h"
+#include "update.h"
+
+#include <cstring>
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
@@ -83,15 +84,13 @@ static void open_socket(int &sockfd, int inet, int port, char* host,
 
     // fetches information on the host
     struct addrinfo hints, *res;
-    char service[256];
 
     memset(&hints, 0, sizeof(hints));
     hints.ai_socktype = SOCK_STREAM;
     hints.ai_family = AF_UNSPEC;
     hints.ai_flags = AI_PASSIVE;
 
-    sprintf(service,"%d",port); // convert the port number to a string
-    ai_err = getaddrinfo(host, service, &hints, &res);
+    ai_err = getaddrinfo(host, std::to_string(port).c_str(), &hints, &res);
     if (ai_err!=0)
       error->one(FLERR,"Error fetching host data. Wrong host name?");
 
diff --git a/src/MISC/fix_srp.cpp b/src/MISC/fix_srp.cpp
index fb502febaf..b7263dbb48 100644
--- a/src/MISC/fix_srp.cpp
+++ b/src/MISC/fix_srp.cpp
@@ -246,10 +246,8 @@ void FixSRP::setup_pre_force(int /*zz*/)
   int nadd_all = 0, ndel_all = 0;
   MPI_Allreduce(&ndel,&ndel_all,1,MPI_INT,MPI_SUM,world);
   MPI_Allreduce(&nadd,&nadd_all,1,MPI_INT,MPI_SUM,world);
-  if (comm->me == 0) {
-    sprintf(str, "Removed/inserted %d/%d bond particles.", ndel_all,nadd_all);
-    error->message(FLERR,str);
-  }
+  if (comm->me == 0)
+    error->message(FLERR,"Removed/inserted {}/{} bond particles.", ndel_all,nadd_all);
 
   // check ghost comm distances
   // warn and change if shorter from estimate
@@ -276,11 +274,9 @@ void FixSRP::setup_pre_force(int /*zz*/)
     cutghostmin = comm->cutghost[2]/length2;
 
   // stop if cutghost is insufficient
-  if (cutneighmax_srp > cutghostmin) {
-    sprintf(str, "Communication cutoff too small for fix srp. "
-            "Need %f, current %f.", cutneighmax_srp, cutghostmin);
-    error->all(FLERR,str);
-  }
+  if (cutneighmax_srp > cutghostmin)
+    error->all(FLERR,"Communication cutoff too small for fix srp. "
+            "Need {:.8}, current {:.8}", cutneighmax_srp, cutghostmin);
 
   // assign tags for new atoms, update map
   atom->tag_extend();
@@ -515,14 +511,8 @@ void FixSRP::post_run()
 
   bigint ndelete = natoms_previous - atom->natoms;
 
-  if (comm->me == 0) {
-    if (screen) fprintf(screen,"Deleted " BIGINT_FORMAT
-                        " atoms, new total = " BIGINT_FORMAT "\n",
-                        ndelete,atom->natoms);
-    if (logfile) fprintf(logfile,"Deleted " BIGINT_FORMAT
-                         " atoms, new total = " BIGINT_FORMAT "\n",
-                         ndelete,atom->natoms);
-  }
+  if (comm->me == 0)
+    utils::logmesg(lmp,"Deleted {} atoms, new total = {}\n",ndelete,atom->natoms);
 
   // verlet calls box_too_small_check() in post_run
   // this check maps all bond partners
diff --git a/src/MISC/pair_srp.cpp b/src/MISC/pair_srp.cpp
index e3a31dda96..67690c8d11 100644
--- a/src/MISC/pair_srp.cpp
+++ b/src/MISC/pair_srp.cpp
@@ -28,24 +28,23 @@ Please contact Timothy Sirk for questions (tim.sirk@us.army.mil).
 
 #include "pair_srp.h"
 
-#include <cmath>
-
-#include <cstring>
 #include "atom.h"
+#include "citeme.h"
 #include "comm.h"
-#include "force.h"
-#include "neighbor.h"
-#include "neigh_list.h"
-#include "memory.h"
-#include "error.h"
 #include "domain.h"
-#include "modify.h"
+#include "error.h"
 #include "fix.h"
 #include "fix_srp.h"
-#include "thermo.h"
+#include "force.h"
+#include "memory.h"
+#include "modify.h"
+#include "neigh_list.h"
+#include "neighbor.h"
 #include "output.h"
-#include "citeme.h"
+#include "thermo.h"
 
+#include <cmath>
+#include <cstring>
 
 using namespace LAMMPS_NS;
 
@@ -79,26 +78,15 @@ PairSRP::PairSRP(LAMMPS *lmp) : Pair(lmp)
   nextra = 1;
   segment = nullptr;
 
-  // generate unique fix-id for this pair style instance
-
-  fix_id = strdup("XX_FIX_SRP");
-  fix_id[0] = '0' + srp_instance / 10;
-  fix_id[1] = '0' + srp_instance % 10;
-  ++srp_instance;
-
-  // create fix SRP instance here
+  // create fix SRP instance here with unique fix id
   // similar to granular pair styles with history,
   //   this should be early enough that FixSRP::pre_exchange()
   //   will be invoked before other fixes that migrate atoms
   //   this is checked for in FixSRP
 
-  char **fixarg = new char*[3];
-  fixarg[0] = fix_id;
-  fixarg[1] = (char *) "all";
-  fixarg[2] = (char *) "SRP";
-  modify->add_fix(3,fixarg);
+  modify->add_fix(fmt::format("{:02d}_FIX_SRP all SRP",srp_instance));
   f_srp = (FixSRP *) modify->fix[modify->nfix-1];
-  delete [] fixarg;
+  ++srp_instance;
 }
 
 /* ----------------------------------------------------------------------
@@ -468,10 +456,8 @@ void PairSRP::init_style()
   if (f_srp != (FixSRP *)modify->fix[ifix])
     error->all(FLERR,"Fix SRP has been changed unexpectedly");
 
-  if (comm->me == 0) {
-    if (screen) fprintf(screen,"Using type %d for bond particles\n",bptype);
-    if (logfile) fprintf(logfile,"Using type %d for bond particles\n",bptype);
-  }
+  if (comm->me == 0)
+    utils::logmesg(lmp,"Using type {} for bond particles\n",bptype);
 
   // set bond and bond particle types in fix srp
   // bonds of this type will be represented by bond particles