bash - Kuinka saada satunnainen 32 heksadesimaalisen merkkijonon komentoriviltä?

original title: "bash - How to get a random string of 32 hexadecimal digits through command line?"


I'd like to put together a command that will print out a string of 32 hexadecimal digits. I've got a Python script that works:

python -c 'import random ; print "".join(map(lambda t: format(t, "02X"), [random.randrange(256) for x in range(16)]))'

This generates output like:


Which is what I need.

On a Mac, I can even do this:

uuidgen | tr -d '-'

However, I don't have access to the more sophisticated scripting languages ruby and python, and I won't be on a Mac (so no uuidgen). I need to stick with more bash'ish tools like sed, awk, /dev/random because I'm on a limited platform. Is there a way to do this?

Haluaisin koota komennon, joka tulostaa 32 heksadesimaalisen numeron merkkijonon. Minulla on Python-skripti, joka toimii: python-c 'import random; tulosta "" .join (kartta (lam ...

Tämä on yhteenveto käännöksen jälkeen. Jos haluat tarkastella koko käännöstä, napsauta käännä-kuvaketta

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  • Translate

    If you have hexdump then:

    hexdump -n 16 -e '4/4 "%08X" 1 "\n"' /dev/random

    should do the job.


    • -n 16 to consume 16 bytes of input (32 hex digits = 16 bytes).
    • 4/4 "%08X" to iterate four times, consume 4 bytes per iteration and print the corresponding 32 bits value as 8 hex digits, with leading zeros, if needed.
    • 1 "\n" to end with a single newline.

    Note: this solution uses /dev/random but it could as well use /dev/urandom. The choice between the two is a complex question and out of the scope of this answer. If you are not sure, have a look maybe at this other question.

  • Translate

    If you are looking for a single command and have openssl installed, see below. Generate random 16 bytes (32 hex symbols) and encode in hex (also -base64 is supported).

    openssl rand -hex 16

  • Anonymous

    There three ways that I know of:

    # Read n bytes from urandom (in hex):
    xxd -l "$n" -p                    /dev/urandom | tr -d " \n" ; echo
    od  -vN "$n" -An -tx1             /dev/urandom | tr -d " \n" ; echo
    hexdump -vn "$n" -e ' /1 "%02x"'  /dev/urandom ; echo

    Use one, comment out the other two.

  • Translate

    Here are a few more options, all of which have the nice property of providing an obvious and easy way to directly select the length of the output string. In all the cases below, changing the '32' to your desired string length is all you need to do.

    #works in bash and busybox, but not in ksh
    tr -dc 'A-F0-9' < /dev/urandom | head -c32
    #works in bash and ksh, but not in busybox
    tr -dc 'A-F0-9' < /dev/urandom | dd status=none bs=1 count=32
    #works in bash, ksh, AND busybox! w00t!
    tr -dc 'A-F0-9' < /dev/urandom | dd bs=1 count=32 2>/dev/null

    EDIT: Tested in different shells.

  • Translate


    xxd -u -l 16 -p /dev/urandom

    Example output: