--- /sys/src/cmd/random.c	Mon Nov  7 11:12:33 2016
+++ /sys/src/cmd/random.c	Mon Nov  7 00:00:00 2016
@@ -0,0 +1,53 @@
+/*
+ * random - print a random number or string
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <mp.h>
+#include <libsec.h>
+
+static int string, prchars, low, high;
+
+static void
+usage(void)
+{
+	fprint(2, "usage: %s [-s nch]\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char *argv[])
+{
+	char *buf, *out;
+
+	ARGBEGIN {
+	case 's':
+		++string;
+		prchars = atoi(EARGF(usage()));
+		break;
+	default:
+		usage();
+		break;
+	} ARGEND
+
+	if (!string) {
+		print("%f\n", (double)ntruerand(~0ul) / (1ull<<32));
+		exits(0);
+	}
+
+	/* fill buf from /dev/random */
+	buf = malloc(prchars + 1);
+	if (buf == nil)
+		sysfatal("out of memory: %r");
+	genrandom((uchar *)buf, prchars);
+	buf[prchars] = '\0';
+
+	/* encode as printable (base64) and print truncated */
+	fmtinstall('[', encodefmt);
+	out = smprint("%.*[", prchars, buf);
+	if (out == nil)
+		sysfatal("out of memory: %r");
+	print("%.*s\n", prchars, out);
+	exits(0);
+}
--- /sys/man/1/random	Mon Nov  7 11:12:34 2016
+++ /sys/man/1/random	Mon Nov  7 00:00:00 2016
@@ -0,0 +1,24 @@
+.TH RANDOM 1
+.SH NAME
+random - print truly random probability or string
+.SH SYNOPSIS
+.B random
+[
+.B -s
+chars
+]
+.SH DESCRIPTION
+.I Random
+normally prints a truly random number between 0 and 1.
+Given
+.BR -s ,
+it instead prints a base-64-encoded truly random string of
+.I chars
+characters.
+.SH SOURCE
+.B /sys/src/cmd/random.c
+.SH SEE ALSO
+.IR rand (2),
+.B /dev/random
+in
+.IR cons (3)