---
name: "bup-random"
section: "1"
platform: "linux"
package: "bup"
version: "0.34-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/bup-random"
---

# bup-random(1)

generate a stream of random output

## NAME

bup-random - generate a stream of random output

## SYNOPSIS

bup random \[-S seed\] \[-fv\] \<numbytes\>

## DESCRIPTION

`bup random` produces a stream of pseudorandom output bytes to stdout. Note: the bytes are *not* generated using a cryptographic algorithm and should never be used for security.

Note that the stream of random bytes will be identical every time `bup random` is run, unless you provide a different `seed` value. This is intentional: the purpose of this program is to be able to run repeatable tests on large amounts of data, so we want identical data every time.

`bup random` generates about 240 megabytes per second on a modern test system (Intel Core2), which is faster than you could achieve by reading data from most disks. Thus, it can be helpful when running microbenchmarks.

## OPTIONS

- \<numbytes\>

  the number of bytes of data to generate. Can be used with the suffices `k`, `M`, or `G` to indicate kilobytes, megabytes, or gigabytes, respectively.

- \-S, --seed=*seed*

  use the given value to seed the pseudorandom number generator. The generated output stream will be identical for every stream seeded with the same value. The default seed is 1. A seed value of 0 is equivalent to 1.

- \-f, --force

  generate output even if stdout is a tty. (Generating random data to a tty is generally considered ill-advised, but you can do if you really want.)

- \-v, --verbose

  print a progress message showing the number of bytes that has been output so far.

## EXAMPLES

-

  ```
  $ bup random 1k | sha1sum
  2108c55d0a2687c8dacf9192677c58437a55db71  -
  $ bup random -S1 1k | sha1sum
  2108c55d0a2687c8dacf9192677c58437a55db71  -
  $ bup random -S2 1k | sha1sum
  f71acb90e135d98dad7efc136e8d2cc30573e71a  -
  $ time bup random 1G >/dev/null
  Random: 1024 Mbytes, done.
  real   0m4.261s
  user   0m4.048s
  sys    0m0.172s
  $ bup random 1G | bup split -t --bench
  Random: 1024 Mbytes, done.
  bup: 1048576.00kbytes in 18.59 secs = 56417.78 kbytes/sec
  1092599b9c7b2909652ef1e6edac0796bfbfc573
  ```

## BUP

Part of the [`bup`(1)](/bup/1.md) suite.

## AUTHORS

Avery Pennarun ⟨apenwarr@gmail.com⟩\\c.