weed | sinon j'ai reussi a recuperer un script sur le net.
Code :
- :
- ##########################################################################
- # Shellscript: rand - return random number
- # Author : Heiner Steven <heiner.steven@odn.de>
- # Date : 1995-09-02
- # Requires : bc, od
- # Category : Desktop
- # SCCS-Id. : @(#) rand 1.9 02/07/17
- ##########################################################################
- # Description
- # o Prints a random number. Uses existing /dev/urandom for good
- # random numbers, otherwise date and time is used.
- # o If /dev/urandom is available, arbitrary large random numbers
- # are supported.
- #
- # Notes
- # o $Max should be used to find out, how many byte should be
- # read from /dev/urandom
- #
- # Changes
- # 1995-09-28 stv Random numbers cannot be maxvalue+1 (0.2)
- # 2000-01-28 stv numbers were too sequential (because of seconds) (1.2)
- # 2001-12-07 stv use $RANDOM variable, if present (1.3)
- # 2002-07-01 stv use /dev/urandom, if present (1.4)
- # 2002-07-02 stv fixed bug (numbers were always multiple of 256) (1.5)
- # 2002-07-16 stv random numbers were not evenly distributed (1.8)
- ##########################################################################
- PN=`basename "$0"` # program name
- VER='1.9'
- # Device returning random bytes. With Solaris 9 /dev/random may block,
- # therefore we prefer the non-blocking /dev/urandom
- RandomDevice=/dev/urandom
- #MaxRand=4294967295 # 2^32 = 4 GB
- # Some shell commands (e.g. Linux "expr" ) have problems with integer values
- # greater than 2^31
- MaxRand=32767
- Usage () {
- echo >&2 "$PN - return random number, $VER (stv '95)
- usage: $PN [maxvalue]
- Prints a random value (1 <= random <= maxvalue) to standard output.
- If no maximum value is specified, `echo \"$MaxRand + 1\" | bc` is the default"
- exit 1
- }
- Msg () {
- for i
- do echo "$PN: $i" >&2
- done
- }
- Fatal () { Msg "$@"; exit 1; }
- joinlines () {
- # "bc" splits very long output lines using the following format:
- # "a\
- # b"
- tr -d '\134\012' # remove backslash and trailing line-feed character
- echo # terminate line using line-feed
- }
- while [ $# -gt 0 ]
- do
- case "$1" in
- --) shift; break;;
- -h) Usage;;
- -*) Usage;;
- *) break;; # First file name
- esac
- shift
- done
- if [ $# -gt 1 ]
- then Usage
- elif [ $# -eq 1 ]
- then
- case "$1" in
- *[!0-9]*) Fatal "illegal number: $1";;
- *) Max=$1;;
- esac
- fi
- : ${Max:=$MaxRand} # Use default value
- # Try different ways of getting a random number
- if [ -c $RandomDevice ]
- then
- # Read 4 bytes from the random device (dd), and interpret them as a
- # 32 bit long unsigned integer (od -t u4).
- #n=`dd if=/dev/urandom bs=1 count=4 2>/dev/null |
- # od -t u4 | awk 'NR==1 {print $2}'`
- # Uncomment the following to use 64 bit random numbers
- #n=`dd if=/dev/urandom bs=1 count=8 2>/dev/null |
- # od -t u8 | awk 'NR==1 {print $2}'`
- # Uncomment the lines below to get a random number with $ndigit
- # digits. Calculate the number of bytes needed as follows:
- # bytes= ... # round log256(10^$ndigit)
- # -> log256(10^x) = x * log256(10) = x * ln(10)/ln(256)
- # = x * .41524101186092029348
- # Example:
- # How many bytes are needed to represent 10 decimal digits:
- # 10 * .41524101186092029348 = 4.1524101186092029348
- # -> 5 bytes needed to represent all 10 digit decimal values
- # from 0..9999999999
- #ndigit=10 # 0..9999999999
- #bytes=5
- ndigit=`expr "$Max" : '.*'` # string length
- # The following calculation may return a result that is one to large
- # because we do not attempt to properly round the value to the next
- # largest integer value.
- bytes=`echo "$ndigit * l(10)/l(256) + 1" | bc -l | cut -d. -f1`
|
hexdigits=`echo "$bytes * 2" | bc`
#echo >&2 "DEBUG: ndigit=<$ndigit> bytes=<$bytes> hexdigits=<$hexdigits>"
n=`(echo ibase=16; dd if=/dev/urandom bs=1 count=$bytes 2>/dev/null |
od -tx1 | # write as hex byte stream
sed -n '$q;p' | # remove last line
cut -d ' ' -f2- | # remove offsets
tr -d ' ' | joinlines |
cut -c1-$hexdigit |
tr '[a-f]' '[A-F]') | # "bc" needs upper case hex chars
bc | joinlines`
elif [ -n "$RANDOM" ]
then
# This shell has a built-in random function (ksh, bash, zsh), which
# probably generates better distributed values than our "date"
# approach.
n=$RANDOM
else
set -- `date '+%H %M %S'`
[ $# -ne 3 ] && Fatal "could not invoke program date"
n=`echo "$$ * $1 * $2 * $3 + $3" | bc`
fi
# Some "expr" commands have problems with large integer values
echo "$n % $Max + 1" | bc | joinlines
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