--- /sys/src/cmd/aux/htmlsanitize.c
+++ /sys/src/cmd/aux/htmlsanitize.c
@@ -0,0 +1,56 @@
+/*
+ * Because sed can't handle really long lines.
+ */
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+
+Biobuf bout;
+
+void
+cat(Biobuf *b)
+{
+	int c;
+
+	while((c = Bgetrune(b)) >= 0){
+		switch(c){
+		case '<':
+			Bprint(&bout, "&lt;");
+			break;
+		case '>':
+			Bprint(&bout, "&gt;");
+			break;
+		case '&':
+			Bprint(&bout, "&amp;");
+			break;
+		default:
+			Bputrune(&bout, c);
+			break;
+		}
+	}
+}
+
+void
+main(int argc, char *argv[])
+{
+	int i;
+	Biobuf *b, bin;
+
+	argv0 = "htmlsanitize";
+	Binit(&bout, 1, OWRITE);
+	if(argc == 1){
+		Binit(&bin, 0, OREAD);
+		cat(&bin);
+	}
+	else for(i=1; i<argc; i++){
+		b = Bopen(argv[i], OREAD);
+		if(b == nil)
+			sysfatal("can't open %s: %r", argv[i]);
+		else{
+			cat(b);
+			Bterm(b);
+		}
+	}
+	Bflush(&bout);
+	exits(0);
+}
--- /n/sources/plan9/sys/src/cmd/aux/mkfile	Thu Aug 16 22:50:45 2012
+++ /sys/src/cmd/aux/mkfile
@@ -14,6 +14,7 @@
 	depend\
 	disksim\
 	getflags\
+	htmlsanitize\
 	lines\
 	listen\
 	listen1\