1RAND(1)                             OpenSSL                            RAND(1)
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NAME

6       openssl-rand, rand - generate pseudo-random bytes
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SYNOPSIS

9       openssl rand [-help] [-out file] [-rand file...]  [-writerand file]
10       [-base64] [-hex] num
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DESCRIPTION

13       This command generates num random bytes using a cryptographically
14       secure pseudo random number generator (CSPRNG).
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16       The random bytes are generated using the RAND_bytes(3) function, which
17       provides a security level of 256 bits, provided it managed to seed
18       itself successfully from a trusted operating system entropy source.
19       Otherwise, the command will fail with a nonzero error code.  For more
20       details, see RAND_bytes(3), RAND(7), and RAND_DRBG(7).
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OPTIONS

23       -help
24           Print out a usage message.
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26       -out file
27           Write to file instead of standard output.
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29       -rand file...
30           A file or files containing random data used to seed the random
31           number generator.  Multiple files can be specified separated by an
32           OS-dependent character.  The separator is ; for MS-Windows, , for
33           OpenVMS, and : for all others.  Explicitly specifying a seed file
34           is in general not necessary, see the "NOTES" section for more
35           information.
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37       [-writerand file]
38           Writes random data to the specified file upon exit.  This can be
39           used with a subsequent -rand flag.
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41       -base64
42           Perform base64 encoding on the output.
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44       -hex
45           Show the output as a hex string.
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NOTES

48       Prior to OpenSSL 1.1.1, it was common for applications to store
49       information about the state of the random-number generator in a file
50       that was loaded at startup and rewritten upon exit. On modern operating
51       systems, this is generally no longer necessary as OpenSSL will seed
52       itself from a trusted entropy source provided by the operating system.
53       The -rand  and -writerand  flags are still supported for special
54       platforms or circumstances that might require them.
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56       It is generally an error to use the same seed file more than once and
57       every use of -rand should be paired with -writerand.
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SEE ALSO

60       RAND_bytes(3), RAND(7), RAND_DRBG(7)
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63       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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65       Licensed under the OpenSSL license (the "License").  You may not use
66       this file except in compliance with the License.  You can obtain a copy
67       in the file LICENSE in the source distribution or at
68       <https://www.openssl.org/source/license.html>.
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721.1.1l                            2021-09-15                           RAND(1)
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