zerotrunc: from Plan 9

R=rsc
CC=plan9port.codebot
http://codereview.appspot.com/4809089

src/cmd/zerotrunc.c

@@ -0,0 +1,26 @@
+/*
+ * cat standard input until you get a zero byte
+ */
+
+#include <u.h>
+#include <libc.h>
+
+void
+main(void)
+{
+	char buf[4096];
+	char *p;
+	int n;
+
+	while((n = read(0, buf, sizeof(buf))) > 0){
+		p = memchr(buf, 0, n);
+		if(p != nil)
+			n = p-buf;
+		if(n > 0)
+			write(1, buf, n);
+		if(p != nil)
+			break;
+	}
+	exits(0);
+}
+