Script for creating random numbers, hex strings, octal strings, random passwords...
This is one of those scripts I should have written a long time ago.
nb the RT-AC86U (Merlin 384.13) does not have rc4. If you want to use that part of the script, use rc5 instead. As it is, it runs perfectly well on the AC68U, and it's also great on other Linux/BSD/unix machines.
This is one of those scripts I should have written a long time ago.
- 32-character hex string:
randoms -f 32 - 32-character hex string with upper-case letters:
randoms -F 32 - 50 random decimal numbers, 8 digits each:
randoms 8 50 - 12 character random password:
randoms -p 12 - 5 random MAC addresses:
randoms -F 12 5 | sed 's!.\{2\}!&:!g ; s!:$!!' - random (but probably invalid) UUID:
randoms -f 32 | sed -E 's/(.{8})(.{4})(.{4})(.{4})/\1-\2-\3-\4-/' - (valid) random UUID (of a known or unknown variant; DCE, NCS, Microsoft, undefined):
randoms -f 31 | sed -E 's/(.{8})(.{4})(.{3})(.{4})/\1-\2-4\3-\4-/'
Code:
#!/bin/sh
## atom's "randoms" script
## v1.01, 18 Nov 2019, (c) atom(@)smasher.org
## v1.01f, 09 may 2022, (c) atom(@)smasher.org
## Distributed under the GNU General Public License
## http://www.gnu.org/copyleft/gpl.html
## originally posted - https://www.snbforums.com/threads/script-for-creating-random-numbers-and-more.60182/
## test for output format option
## thanks Dabombber for this section of code :)
case "$1" in
'-f')
## this gives hexadecimal output
chars_match='0-9a-f'
shift
;;
'-F')
## this gives hexadecimal output, upper-case letters
chars_match='0-9A-F'
shift
;;
'-8')
## this gives octal output
chars_match='0-7'
shift
;;
'-p')
## random passwords
chars_match='0-9a-zA-Z<>/\?!@#$%^&*()+=_,.-'
## for random passwords, edit the character-set as desired
## nb, '!-~' include all "normal" "printable" ASCII characters
shift
;;
*)
## default is decimal output
chars_match='0-9'
;;
esac
#### 1st argument
## $1 is number of digits output per line.
## 18 is a default, because that's what usually what expr can safely handle.
## this makes it easy to use this script for deriving random numbers within
## a given range, eg for getting random numbers between 1-37, inclusive:
## expr $( randoms ) % 37 + 1
digits_output=${1:-18}
#### 2nd argument
## $2 is number of output lines
## defaults to 1
lines_output=${2:-1}
## this displays on "-h", "--help", or any improper use
help () {
echo "$(basename $0): usage:"
echo " $(basename $0) [-f|-F|-8|-p] [d [l]]"
echo
echo ' -f: hexadecimal output'
echo ' -F: hexadecimal output, with upper-case letters'
echo ' -8: octal output'
echo ' -p: random passwords'
echo ' d: number of digits (or characters) output per line'
echo ' l: number of output lines'
echo ' ** Default output is decimal format, 18 digits, 1 line'
echo
echo 'Examples:'
echo '* Print 5 random decimal strings, each with 3 digits:'
echo " $(basename $0) 3 5"
echo
echo '* Print 1 random hexadecimal string with 32 digits:'
echo " $(basename $0) -f 32"
echo
echo '* Print 1 random decimal string with 300 digits:'
echo " $(basename $0) 300"
echo
echo '* Print 1 random password string with 12 characters:'
echo " $(basename $0) -p 12"
echo
echo "* Print 5 random MAC addresses:"
echo " $(basename $0) -F 12 5 | sed 's!.\{2\}!&:!g ; s!:\$!!' "
echo
echo "* Print a random (but probably invalid) UUID:"
printf " $(basename $0) -f 32 | sed -E 's/(.{8})(.{4})(.{4})(.{4})/\\\1-\\\2-\\\3-\\\4-/'\n"
echo
echo "* Print a (valid) random UUID (of a known or unknown variant; DCE, NCS, Microsoft, undefined):"
printf " $(basename $0) -f 31 | sed -E 's/(.{8})(.{4})(.{3})(.{4})/\\\1-\\\2-4\\\3-\\\4-/'\n"
echo
exit 1
}
## test that numeric arguments are sensible
## or print help (to stderr) and exit (exit status 1)
[ 0 -lt ${digits_output} ] 2> /dev/random || help 1>&2
[ 0 -lt ${lines_output} ] 2> /dev/random || help 1>&2
n=1
## go through this loop once per line of output
while [ ${lines_output} -ge ${n} ]
do
## this gives output strings of arbitrary length
tr -cd "${chars_match}" < /dev/urandom | head -c ${digits_output}
echo
n=$(( $n + 1 ))
done
exit 0
####################################
## NOTE THE "exit" DIRECTLY ABOVE ##
## WHAT'S BELOW HERE WILL NOT RUN ##
####################################
## for systems with wonky /dev/urandom, this (below) may be more robust.
## it's actually concerning how often "openssl enc -rc4" does better
## than /dev/urandom, according to dieharder, although there are still
## advantages to using /dev/urandom (such as portability and periodic reseeding)
## this is included here for reference and experimentation. have fun with it.
### rc4 is fast and does a good job passing the dieharder tests.
### "tail -c +17" strips out the "Salted__xxxxxxxx" string.
### "2> /dev/random" pipes openssl's errors into /dev/random; use /dev/null if needed.
### "head -c 16 /dev/urandom" derives a 128 bit password, read by "-pass stdin".
n=1
head -c 16 /dev/urandom | openssl enc -rc4 -pass stdin -in /dev/zero 2> /dev/random | tail -c +17 | while :
do
## go through this loop once per line of output
## this gives output strings of arbitrary length
tr -cd "${chars_match}" | head -c ${digits_output}
echo
n=$(( $n + 1 ))
[ ${lines_output} -ge ${n} ] || exit 0
done
##############################################
## and another alternative to /dev/urandom, ##
## this time using "haveged" ##
##############################################
## stderr is directed from haveged into /dev/random,
## if needed, direct that into /dev/null
n=1
## go through this loop once per line of output
haveged -n 0 2> /dev/random | while [ ${lines_output} -ge ${n} ]
do
## this gives output strings of arbitrary length
tr -cd "${chars_match}" | head -c ${digits_output}
echo
n=$(( $n + 1 ))
donenb the RT-AC86U (Merlin 384.13) does not have rc4. If you want to use that part of the script, use rc5 instead. As it is, it runs perfectly well on the AC68U, and it's also great on other Linux/BSD/unix machines.
Last edited:
