diff -u gawk-3.1.6/awk.h gawk-3.1.6-inplace-edit/awk.h
--- gawk-3.1.6/awk.h	2007-10-01 04:50:43.000000000 +0900
+++ gawk-3.1.6-inplace-edit/awk.h	2009-01-09 16:37:23.047625000 +0900
@@ -801,6 +801,10 @@
 
 extern char casetable[];	/* for case-independent regexp matching */
 
+#if 2
+extern int do_inplace_edit;
+#endif
+
 /* ------------------------- Pseudo-functions ------------------------- */
 
 #define is_identchar(c)		(isalnum(c) || (c) == '_')
diff -u gawk-3.1.6/builtin.c gawk-3.1.6-inplace-edit/builtin.c
--- gawk-3.1.6/builtin.c	2007-10-01 04:57:05.000000000 +0900
+++ gawk-3.1.6-inplace-edit/builtin.c	2009-01-09 16:37:23.047625000 +0900
@@ -1315,6 +1315,77 @@
 	return r;
 }
 
+#if 2
+/*
+ *
+ */
+static FILE* current_tmpfile_fp = NULL;
+static char current_tmpfile_name[1024] = "";
+static const char *current_file_name = NULL;
+
+/*
+ * close_tmpfile
+ */
+
+int
+close_tmpfile()
+{
+    char backupfilename[1024];
+
+    if (!current_tmpfile_fp)
+        return 0;
+
+    //fprintf(stderr, "copy %s -> %s\n", current_file_name, current_tmpfile_name);
+    fclose(current_tmpfile_fp);
+    snprintf(backupfilename, sizeof backupfilename, "%s.~", current_file_name);
+#if _WIN32
+    /* In Windows, rename() fail when already exists backupfile.
+     * Then we have to delete the file before call of rename()
+     */
+    unlink(backupfilename);
+#endif
+    rename(current_file_name, backupfilename);       /* make backup */
+    rename(current_tmpfile_name, current_file_name); /* update */
+
+    current_tmpfile_fp = NULL;
+    return 0;
+}
+
+/* 
+ * get_current_tmp ---
+ */
+
+FILE*
+get_current_tmp()
+{
+    return current_tmpfile_fp;
+}
+
+/*
+ * create_filen_for_inplace_edit ---
+ */
+FILE*
+create_file_for_inplace_edit(const char* filename)
+{
+    char *p;
+
+    if (current_tmpfile_fp) {
+        close_tmpfile();
+    }
+
+    current_file_name = strdup(filename);
+#ifndef _WIN32
+    snprintf(current_tmpfile_name, sizeof current_tmpfile_name, "%sXXXXXX", filename);
+    p = mkstemp(current_tmpfile_name);
+#else
+    p = tmpnam(current_tmpfile_name);
+#endif
+    current_tmpfile_fp = fopen(p, "wb+");
+
+    return current_tmpfile_fp;
+}
+#endif
+
 /*
  * redirect_to_fp --- return fp for redirection, NULL on failure
  * or stdout if no redirection, used by all print routines
diff -u gawk-3.1.6/io.c gawk-3.1.6-inplace-edit/io.c
--- gawk-3.1.6/io.c	2007-08-12 04:39:49.000000000 +0900
+++ gawk-3.1.6-inplace-edit/io.c	2009-01-09 16:37:23.094500000 +0900
@@ -279,17 +279,31 @@
 	static IOBUF *curfile = NULL;
 	static IOBUF mybuf;
 	const char *fname;
+#if 2
+	extern int create_file_for_inplace_edit(const char*);
+	extern int close_tmpfile();
+#endif
 
 	if (skipping) {
 		if (curfile != NULL)
 			iop_close(curfile);
 		curfile = NULL;
+#if 2
+		if (do_inplace_edit) {
+			close_tmpfile();
+		}
+#endif
 		return NULL;
 	}
 	if (curfile != NULL) {
 		if (at_eof(curfile)) {
 			(void) iop_close(curfile);
 			curfile = NULL;
+#if 2
+			if (do_inplace_edit) {
+				close_tmpfile();
+			}
+#endif
 		} else
 			return curfile;
 	}
@@ -324,6 +338,11 @@
 			FILENAME_node->var_value = dupnode(arg);
 			FNR = 0;
 			i++;
+#if 2
+			if (do_inplace_edit) {
+				create_file_for_inplace_edit(fname);
+			}
+#endif
 			break;
 		}
 	}
diff -u gawk-3.1.6/main.c gawk-3.1.6-inplace-edit/main.c
--- gawk-3.1.6/main.c	2007-10-01 04:55:18.000000000 +0900
+++ gawk-3.1.6-inplace-edit/main.c	2009-01-09 16:42:49.907000000 +0900
@@ -196,6 +196,9 @@
 #if defined(YYDEBUG) || defined(GAWKDEBUG)
 	{ "parsedebug",		no_argument,		NULL,		'D' },
 #endif
+#if 2
+	{ "inplace-edit",	optional_argument,	NULL,		'i' },
+#endif
 	{ NULL, 0, NULL, '\0' }
 };
 
@@ -432,6 +435,12 @@
 #endif
 			/* if not debugging, fall through */
 
+#if 2
+		case 'i':
+			do_inplace_edit = TRUE;
+			break;
+#endif
+
 		case '?':
 		default:
 			/*