diff -Naur lammps-24Jan10/src/error.cpp lammps-24Jan10-patched/src/error.cpp
--- lammps-24Jan10/src/error.cpp	2007-10-03 16:22:30.000000000 +0000
+++ lammps-24Jan10-patched/src/error.cpp	2010-01-30 18:40:17.000000000 +0000
@@ -22,14 +22,20 @@
 
 /* ---------------------------------------------------------------------- */
 
-Error::Error(LAMMPS *lmp) : Pointers(lmp) {}
+Error::Error(LAMMPS *lmp, int library) : Pointers(lmp) {
+  noexit = library;
+}
+
+Error::Error(LAMMPS *lmp) : Pointers(lmp) {
+  noexit = 0;
+}
 
 /* ----------------------------------------------------------------------
    called by all procs in universe
    close all output, screen, and log files in world and universe
 ------------------------------------------------------------------------- */
 
-void Error::universe_all(const char *str)
+void Error::universe_all(const char *str) throw (LAMMPSexception)
 {
   MPI_Barrier(universe->uworld);
 
@@ -38,6 +44,11 @@
     if (universe->ulogfile) fprintf(universe->ulogfile,"ERROR: %s\n",str);
   }
 
+  if (noexit) {
+    last_error_msg = str;
+    throw LAMMPSexception(str);
+  }
+
   if (output) delete output;
   if (universe->nworlds > 1) {
     if (screen && screen != stdout) fclose(screen);
@@ -65,7 +76,7 @@
    close all output, screen, and log files in world
 ------------------------------------------------------------------------- */
 
-void Error::all(const char *str)
+void Error::all(const char *str) throw (LAMMPSexception)
 {
   MPI_Barrier(world);
 
@@ -77,6 +88,11 @@
     if (logfile) fprintf(logfile,"ERROR: %s\n",str);
   }
 
+  if (noexit) {
+    last_error_msg = str;
+    throw LAMMPSexception(str);
+  }
+
   if (output) delete output;
   if (screen && screen != stdout) fclose(screen);
   if (logfile) fclose(logfile);
@@ -110,3 +126,23 @@
 {
   if (screen) fprintf(screen,"WARNING: %s\n",str);
 }
+
+/* ----------------------------------------------------------------------
+   called only when the library interface is used
+   used to clear the error status before a library call
+------------------------------------------------------------------------- */
+
+void Error::clear()
+{
+ last_error_msg = NULL;
+}
+
+/* ----------------------------------------------------------------------
+   called only when the library interface is used
+   returns the last error trapped, if any
+------------------------------------------------------------------------- */
+
+const char *Error::last_error()
+{
+  return last_error_msg;
+}
diff -Naur lammps-24Jan10/src/error.h lammps-24Jan10-patched/src/error.h
--- lammps-24Jan10/src/error.h	2010-01-12 01:37:48.000000000 +0000
+++ lammps-24Jan10-patched/src/error.h	2010-01-30 18:40:28.000000000 +0000
@@ -15,19 +15,27 @@
 #define LMP_ERROR_H
 
 #include "pointers.h"
+#include "exception.h"
 
 namespace LAMMPS_NS {
 
 class Error : protected Pointers {
  public:
+  Error(class LAMMPS *, int);
   Error(class LAMMPS *);
 
-  void universe_all(const char *);
+  void universe_all(const char *) throw (LAMMPSexception);
   void universe_one(const char *);
 
-  void all(const char *);
+  void all(const char *) throw (LAMMPSexception);
   void one(const char *);
   void warning(const char *);
+  
+  void clear();
+  const char *last_error();
+ private:
+  int noexit;
+  const char *last_error_msg;
 };
 
 }
diff -Naur lammps-24Jan10/src/exception.cpp lammps-24Jan10-patched/src/exception.cpp
--- lammps-24Jan10/src/exception.cpp	1970-01-01 00:00:00.000000000 +0000
+++ lammps-24Jan10-patched/src/exception.cpp	2010-01-30 18:40:17.000000000 +0000
@@ -0,0 +1,15 @@
+#include "exception.h"
+
+using namespace LAMMPS_NS;
+
+
+LAMMPSexception::LAMMPSexception(const char *msg) : exception() {
+  message = msg;
+}
+
+const char *LAMMPSexception::what() const throw()
+{
+  return message;
+}
+
+
diff -Naur lammps-24Jan10/src/exception.h lammps-24Jan10-patched/src/exception.h
--- lammps-24Jan10/src/exception.h	1970-01-01 00:00:00.000000000 +0000
+++ lammps-24Jan10-patched/src/exception.h	2010-01-30 18:40:28.000000000 +0000
@@ -0,0 +1,21 @@
+#ifndef EXCEPTION_H
+#define EXCEPTION_H
+
+#include <exception>
+
+using namespace std;
+
+namespace LAMMPS_NS {
+  
+class LAMMPSexception: public exception {
+ public:
+  LAMMPSexception(const char *);
+ 
+  const char* what() const throw();
+
+ private: 
+  const char *message;
+};
+
+}
+#endif
diff -Naur lammps-24Jan10/src/lammps.cpp lammps-24Jan10-patched/src/lammps.cpp
--- lammps-24Jan10/src/lammps.cpp	2010-01-14 00:33:02.000000000 +0000
+++ lammps-24Jan10-patched/src/lammps.cpp	2010-01-30 18:40:17.000000000 +0000
@@ -41,8 +41,18 @@
 
 LAMMPS::LAMMPS(int narg, char **arg, MPI_Comm communicator)
 {
+  init(narg, arg, communicator, 0);
+}
+
+LAMMPS::LAMMPS(int narg, char **arg, MPI_Comm communicator, int aslibrary)
+{
+  init(narg, arg, communicator, aslibrary);
+}
+
+void LAMMPS::init(int narg, char **arg, MPI_Comm communicator, int aslibrary)
+{
   memory = new Memory(this);
-  error = new Error(this);
+  error = new Error(this, aslibrary);
   universe = new Universe(this,communicator);
   output = NULL;
 
diff -Naur lammps-24Jan10/src/lammps.h lammps-24Jan10-patched/src/lammps.h
--- lammps-24Jan10/src/lammps.h	2010-01-12 01:37:48.000000000 +0000
+++ lammps-24Jan10-patched/src/lammps.h	2010-01-30 18:40:28.000000000 +0000
@@ -44,10 +44,13 @@
   FILE *logfile;                 // logfile
 
   LAMMPS(int, char **, MPI_Comm);
+  LAMMPS(int, char **, MPI_Comm, int aslibrary);
   ~LAMMPS();
   void create();
   void init();
   void destroy();
+ private:
+  void init(int, char **, MPI_Comm, int aslibrary);
 };
 
 }
diff -Naur lammps-24Jan10/src/library.cpp lammps-24Jan10-patched/src/library.cpp
--- lammps-24Jan10/src/library.cpp	2009-08-06 22:25:12.000000000 +0000
+++ lammps-24Jan10-patched/src/library.cpp	2010-01-30 18:40:17.000000000 +0000
@@ -23,17 +23,36 @@
 #include "update.h"
 #include "domain.h"
 #include "modify.h"
+#include "exception.h"
+#include "error.h"
 
 using namespace LAMMPS_NS;
 
 /* ----------------------------------------------------------------------
+   return the last error produced by LAMMPS, or NULL. Required by C
+------------------------------------------------------------------------- */
+
+const char *lammps_last_error(void *ptr)
+{  
+  LAMMPS *lmp = (LAMMPS *) ptr;
+  return lmp->error->last_error();
+}
+
+
+/* ----------------------------------------------------------------------
    create an instance of LAMMPS and return pointer to it
    pass in command-line args and MPI communicator to run on
 ------------------------------------------------------------------------- */
 
 void lammps_open(int argc, char **argv, MPI_Comm communicator, void **ptr)
 {
-  LAMMPS *lmp = new LAMMPS(argc,argv,communicator);
+  LAMMPS *lmp;
+  try {
+    lmp = new LAMMPS(argc, argv, communicator, 1);
+  } catch (LAMMPSexception e) {
+    *ptr = NULL;
+    return;
+  }
   *ptr = (void *) lmp;
 }
 
@@ -44,7 +63,12 @@
 void lammps_close(void *ptr)
 {
   LAMMPS *lmp = (LAMMPS *) ptr;
-  delete lmp;
+  lmp->error->clear();
+  try {
+    delete lmp;
+  } catch (LAMMPSexception e) {
+    return;
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -54,7 +78,12 @@
 void lammps_file(void *ptr, char *str)
 {
   LAMMPS *lmp = (LAMMPS *) ptr;
-  lmp->input->file(str);
+  lmp->error->clear();
+  try {
+    lmp->input->file(str);
+  } catch (LAMMPSexception e) {
+    return;
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -64,7 +93,14 @@
 char *lammps_command(void *ptr, char *str)
 {
   LAMMPS *lmp = (LAMMPS *) ptr;
-  return lmp->input->one(str);
+  char *retval;
+  lmp->error->clear();
+  try { 
+    retval = lmp->input->one(str);
+  } catch (LAMMPSexception e) {
+    retval = NULL;
+  }
+  return retval;
 }
 
 /* ----------------------------------------------------------------------
diff -Naur lammps-24Jan10/src/library.h lammps-24Jan10-patched/src/library.h
--- lammps-24Jan10/src/library.h	2009-08-06 22:21:38.000000000 +0000
+++ lammps-24Jan10-patched/src/library.h	2010-01-30 18:40:28.000000000 +0000
@@ -17,6 +17,7 @@
 */
 
 #include "mpi.h"
+#include "error.h"
 
 /* ifdefs allow this file to be included in a C program */
 
@@ -24,6 +25,8 @@
 extern "C" {
 #endif
 
+const char *lammps_last_error(void *ptr);
+
 void lammps_open(int, char **, MPI_Comm, void **);
 void lammps_close(void *);
 void lammps_file(void *, char *);