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Author Message
 Random alphanumeric sequence parsing
I would like to use /dev/urandom (linux red hat 7.3 kernel 2.4) to
generate long sequence of alphanumeric characters. I used the below
mentioned command but I got several lines while I'd like to have an
"uninterrupted" stream of characters. Any idea or corrections?
Thank you in advanced.

[root]# cat </dev/urandom | head -n 15 | sed -e 's/[^0-9a-zA-Z]//g'|
sed -e 's/\\n//g'

 Sun, 10 Sep 2006 22:32:20 GMT   
 Random alphanumeric sequence parsing
2004-03-24, 06:32(-08), Sara:

tr -cd 0-9a-zA-Z < /dev/urandom

Stphane                      ["Stephane.Chazelas" at ""]

 Sun, 10 Sep 2006 22:50:21 GMT   
 Random alphanumeric sequence parsing

   That _is_ an "uninterrupted" stream of characters; a newline is a
   character like any other.

   Besides, when you pipe through "head -n 15", you are specifically
   asking for 15 lines. Those lines will be of random length; how long
   a string do you want?

   To remove all non alphanumeric characters, pipe the bytes through
   tr's complement option:

tr -cd 'a-zA-Z0-9'

   I have never used /dev/random, but when I tried it just now, it was
   incredibly slow. I'd use the shell to produce the string:

randstr() {
    case $1 in
        "-l") length=$2; shift 2 ;;
        *) length=1 ;;
    while [ ${#_RANDSTR} -lt $length ]
      eval _RANDSTR=${_RANDSTR}${sep}\${$(( $RANDOM % $# + 1 ))}

lower="a b c d e f g h i j k l m n o p q r s t u v w x y z"
upper="A B C D E F G H I J K L M N O P Q R S T U V W X Y Z"
numbers="0 1 2 3 4 5 6 7 8 9"

randstr -l 666 $upper $lower $numbers
echo $_RANDSTR

    Chris F.A. Johnson        
    My code (if any) in this post is copyright 2004, Chris F.A. Johnson
    and may be copied under the terms of the GNU General Public License

 Mon, 11 Sep 2006 01:17:35 GMT   
 Random alphanumeric sequence parsing
Dnia 2004-03-24, Sara napisal:
I've recently almost the same problem, and this is my solution:


unset PASS
for PART in `dd if=/dev/urandom bs=1024 count=10 2> /dev/null | strings`; do
  test ${#PASS} -gt 10 && break

echo "${PASS# }"

This generates nice passwords from 11 to ~16 chars length :)

Stanislaw Klekot

 Wed, 13 Sep 2006 03:00:14 GMT   
   [ 4 post ] 

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