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Top Forums Shell Programming and Scripting Generate 16 digit positive random Numbers Post 302688187 by drl on Saturday 18th of August 2012 06:13:20 AM
Old 08-18-2012
Hi, fpmurphy.
Quote:
Originally Posted by fpmurphy
Code:
tr -dc A-Za-z0-9 </dev/urandom |  head -c 14

Probably a typo, I had better luck with:
Code:
tr -dc '0-9' </dev/urandom |  head -c 14

producing, for example:
Code:
63443697797894

rather than:
Code:
IzjDQNR6LxvwOE

Users should note also:
Code:
       The kernel random-number generator is designed to produce a small
       amount of high-quality seed material to seed a cryptographic pseudo-
       random number generator (CPRNG).  It is designed for security, not
       speed, and is poorly suited to generating large amounts of random data.
       Users should be very economical in the amount of seed material that
       they read from /dev/urandom (and /dev/random); unnecessarily reading
       large quantities of data from this device will have a negative impact
       on other users of the device.
excerpt from man urandom

Best wishes ... cheers, drl
 

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SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.8.4 2005-05-03 SHELL-QUOTE(1p)
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