diff --git a/frontends/yasm/yasm.c b/frontends/yasm/yasm.c
index ffb095cc..d7db7939 100644
--- a/frontends/yasm/yasm.c
+++ b/frontends/yasm/yasm.c
@@ -1,4 +1,4 @@
-/* $Id: yasm.c,v 1.4 2001/07/11 23:16:50 peter Exp $
+/* $Id: yasm.c,v 1.5 2001/08/18 22:15:12 peter Exp $
  * Program entry point, command line parsing
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -21,19 +21,39 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 extern int yydebug;
+extern FILE *yyin;
 
 extern int yyparse(void);
 
+char *filename = (char *)NULL;
 unsigned int line_number = 1;
 unsigned int mode_bits = 32;
 
 int
-main (void)
+main (int argc, char *argv[])
 {
+    FILE *in;
+
     yydebug = 1;
+
+    if(argc==2) {
+	in = fopen(argv[1], "rt");
+	if(!in) {
+	    fprintf(stderr, "could not open file `%s'\n", argv[1]);
+	    return EXIT_FAILURE;
+	}
+	filename = strdup(argv[1]);
+	yyin = in;
+    } else
+	filename = strdup("<UNKNOWN>");
+
     yyparse();
+
+    if(filename)
+	free(filename);
     return EXIT_SUCCESS;
 }
 
diff --git a/libyasm/bytecode.c b/libyasm/bytecode.c
index 9af7ad0d..54c7c8e4 100644
--- a/libyasm/bytecode.c
+++ b/libyasm/bytecode.c
@@ -1,4 +1,4 @@
-/* $Id: bytecode.c,v 1.14 2001/07/25 00:33:10 peter Exp $
+/* $Id: bytecode.c,v 1.15 2001/08/18 22:15:12 peter Exp $
  * Bytecode utility functions
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -21,6 +21,7 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include "globals.h"
 #include "bytecode.h"
 #include "errwarn.h"
@@ -232,7 +233,7 @@ BuildBC_Common (bytecode *bc)
 {
     bc->len = 0;
 
-    bc->filename = (char *)NULL;
+    bc->filename = strdup(filename);
     bc->lineno = line_number;
 
     bc->offset = 0;
diff --git a/libyasm/errwarn.c b/libyasm/errwarn.c
index b6c4e263..eaf6292a 100644
--- a/libyasm/errwarn.c
+++ b/libyasm/errwarn.c
@@ -1,4 +1,4 @@
-/* $Id: errwarn.c,v 1.17 2001/07/25 00:33:10 peter Exp $
+/* $Id: errwarn.c,v 1.18 2001/08/18 22:15:12 peter Exp $
  * Error and warning reporting and related functions.
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -72,7 +72,8 @@ static char *err_msgs[] = {
     "unexpected end of file in string",
     "expression syntax error",
     "floating-point constant encountered in `%s'",
-    "non-floating-point value encountered in `%s'"
+    "non-floating-point value encountered in `%s'",
+    "could not open file `%s'"
 };
 
 /* Warning messages.  Match up with warn_num enum in errwarn.h. */
@@ -275,7 +276,7 @@ void
 OutputError (void)
 {
     if(last_err_num != ERR_NONE)
-	fprintf(stderr, "filename:%u: %s\n", line_number, last_err);
+	fprintf(stderr, "%s:%u: %s\n", filename, line_number, last_err);
     last_err_num = ERR_NONE;
 }
 
@@ -284,7 +285,8 @@ void
 OutputWarning (void)
 {
     if(last_warn_num != WARN_NONE)
-	fprintf(stderr, "filename:%u: warning: %s\n", line_number, last_warn);
+	fprintf(stderr, "%s:%u: warning: %s\n", filename, line_number,
+	    last_warn);
     last_warn_num = WARN_NONE;
 }
 
diff --git a/libyasm/errwarn.h b/libyasm/errwarn.h
index 51bf7175..5c76a17b 100644
--- a/libyasm/errwarn.h
+++ b/libyasm/errwarn.h
@@ -1,4 +1,4 @@
-/* $Id: errwarn.h,v 1.11 2001/07/25 00:33:10 peter Exp $
+/* $Id: errwarn.h,v 1.12 2001/08/18 22:15:12 peter Exp $
  * Error and warning reporting and related functions header file.
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -50,7 +50,8 @@ typedef enum {
     ERR_STRING_EOF,
     ERR_EXPR_SYNTAX,
     ERR_DECLDATA_FLOAT,
-    ERR_DECLDATA_EXPR
+    ERR_DECLDATA_EXPR,
+    ERR_FILE_OPEN
 } err_num;
 
 /* Warning constants.  Match up with warn_msgs in errwarn.c. */
diff --git a/libyasm/linemgr.h b/libyasm/linemgr.h
index 30153d4f..e33463c8 100644
--- a/libyasm/linemgr.h
+++ b/libyasm/linemgr.h
@@ -1,4 +1,4 @@
-/* $Id: linemgr.h,v 1.3 2001/06/28 21:22:01 peter Exp $
+/* $Id: linemgr.h,v 1.4 2001/08/18 22:15:12 peter Exp $
  * Globals header file
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -22,6 +22,7 @@
 #ifndef YASM_GLOBALS_H
 #define YASM_GLOBALS_H
 
+extern char *filename;
 extern unsigned int line_number;
 extern unsigned int mode_bits;
 extern struct symrec_s *locallabel_base;
diff --git a/src/bytecode.c b/src/bytecode.c
index 9af7ad0d..54c7c8e4 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -1,4 +1,4 @@
-/* $Id: bytecode.c,v 1.14 2001/07/25 00:33:10 peter Exp $
+/* $Id: bytecode.c,v 1.15 2001/08/18 22:15:12 peter Exp $
  * Bytecode utility functions
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -21,6 +21,7 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include "globals.h"
 #include "bytecode.h"
 #include "errwarn.h"
@@ -232,7 +233,7 @@ BuildBC_Common (bytecode *bc)
 {
     bc->len = 0;
 
-    bc->filename = (char *)NULL;
+    bc->filename = strdup(filename);
     bc->lineno = line_number;
 
     bc->offset = 0;
diff --git a/src/errwarn.c b/src/errwarn.c
index b6c4e263..eaf6292a 100644
--- a/src/errwarn.c
+++ b/src/errwarn.c
@@ -1,4 +1,4 @@
-/* $Id: errwarn.c,v 1.17 2001/07/25 00:33:10 peter Exp $
+/* $Id: errwarn.c,v 1.18 2001/08/18 22:15:12 peter Exp $
  * Error and warning reporting and related functions.
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -72,7 +72,8 @@ static char *err_msgs[] = {
     "unexpected end of file in string",
     "expression syntax error",
     "floating-point constant encountered in `%s'",
-    "non-floating-point value encountered in `%s'"
+    "non-floating-point value encountered in `%s'",
+    "could not open file `%s'"
 };
 
 /* Warning messages.  Match up with warn_num enum in errwarn.h. */
@@ -275,7 +276,7 @@ void
 OutputError (void)
 {
     if(last_err_num != ERR_NONE)
-	fprintf(stderr, "filename:%u: %s\n", line_number, last_err);
+	fprintf(stderr, "%s:%u: %s\n", filename, line_number, last_err);
     last_err_num = ERR_NONE;
 }
 
@@ -284,7 +285,8 @@ void
 OutputWarning (void)
 {
     if(last_warn_num != WARN_NONE)
-	fprintf(stderr, "filename:%u: warning: %s\n", line_number, last_warn);
+	fprintf(stderr, "%s:%u: warning: %s\n", filename, line_number,
+	    last_warn);
     last_warn_num = WARN_NONE;
 }
 
diff --git a/src/errwarn.h b/src/errwarn.h
index 51bf7175..5c76a17b 100644
--- a/src/errwarn.h
+++ b/src/errwarn.h
@@ -1,4 +1,4 @@
-/* $Id: errwarn.h,v 1.11 2001/07/25 00:33:10 peter Exp $
+/* $Id: errwarn.h,v 1.12 2001/08/18 22:15:12 peter Exp $
  * Error and warning reporting and related functions header file.
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -50,7 +50,8 @@ typedef enum {
     ERR_STRING_EOF,
     ERR_EXPR_SYNTAX,
     ERR_DECLDATA_FLOAT,
-    ERR_DECLDATA_EXPR
+    ERR_DECLDATA_EXPR,
+    ERR_FILE_OPEN
 } err_num;
 
 /* Warning constants.  Match up with warn_msgs in errwarn.c. */
diff --git a/src/globals.h b/src/globals.h
index a5fe788f..5083ebdc 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1,4 +1,4 @@
-/* $Id: globals.h,v 1.3 2001/06/28 21:22:01 peter Exp $
+/* $Id: globals.h,v 1.4 2001/08/18 22:15:12 peter Exp $
  * Globals header file
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -22,6 +22,7 @@
 #ifndef YASM_GLOBALS_H
 #define YASM_GLOBALS_H
 
+extern char *filename;
 extern unsigned int line_number;
 extern unsigned int mode_bits;
 extern struct symrec_s *locallabel_base;
diff --git a/src/linemgr.h b/src/linemgr.h
index 30153d4f..e33463c8 100644
--- a/src/linemgr.h
+++ b/src/linemgr.h
@@ -1,4 +1,4 @@
-/* $Id: linemgr.h,v 1.3 2001/06/28 21:22:01 peter Exp $
+/* $Id: linemgr.h,v 1.4 2001/08/18 22:15:12 peter Exp $
  * Globals header file
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -22,6 +22,7 @@
 #ifndef YASM_GLOBALS_H
 #define YASM_GLOBALS_H
 
+extern char *filename;
 extern unsigned int line_number;
 extern unsigned int mode_bits;
 extern struct symrec_s *locallabel_base;
diff --git a/src/main.c b/src/main.c
index 28bee46f..68cbcaea 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,4 +1,4 @@
-/* $Id: main.c,v 1.4 2001/07/11 23:16:50 peter Exp $
+/* $Id: main.c,v 1.5 2001/08/18 22:15:12 peter Exp $
  * Program entry point, command line parsing
  *
  *  Copyright (C) 2001  Peter Johnson
@@ -21,19 +21,39 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 extern int yydebug;
+extern FILE *yyin;
 
 extern int yyparse(void);
 
+char *filename = (char *)NULL;
 unsigned int line_number = 1;
 unsigned int mode_bits = 32;
 
 int
-main (void)
+main (int argc, char *argv[])
 {
+    FILE *in;
+
     yydebug = 1;
+
+    if(argc==2) {
+	in = fopen(argv[1], "rt");
+	if(!in) {
+	    fprintf(stderr, "could not open file `%s'\n", argv[1]);
+	    return EXIT_FAILURE;
+	}
+	filename = strdup(argv[1]);
+	yyin = in;
+    } else
+	filename = strdup("<UNKNOWN>");
+
     yyparse();
+
+    if(filename)
+	free(filename);
     return EXIT_SUCCESS;
 }