examples/scripts/krand.bash

   1 # Originally
   2 #
   3 # From: bsh20858@news.fhda.edu (Brian S Hiles)
   4 # Newsgroups: comp.unix.shell
   5 # Subject: Re: getting random numbers
   6 # Date: 23 Jan 1997 23:27:30 GMT
   7 # Message-ID: <5c8s52$eif@tiptoe.fhda.edu>
   8
   9 # @(#) krand  Produces a random number within integer limits
  10 # "krand" Korn shell script generates a random number in a
  11 # specified range with an optionally specified ``seed'' value.
  12 # Author: Peter Turnbull, May 1993
  13 # Modified by: Becca Thomas, January 1994
  14
  15 # changed the optional third argument to a -s option, converted to
  16 # bash v2 syntax -- chet@po.cwru.edu
  17
  18 PROGNAME=${0##*/}
  19 USAGE="usage: $PROGNAME [-s seed] lower-limit upper-limit"
  20
  21 Seed=$$                 # Initialize random-number seed value with PID
  22
  23 usage()
  24 {
  25         echo ${PROGNAME}: "$USAGE" >&2
  26 }
  27
  28 errexit()
  29 {
  30         echo ${PROGNAME}: "$@" >&2
  31         exit 1
  32 }
  33
  34 # Process command-line arguments:
  35 while getopts "s:" opt; do
  36         case "$opt" in
  37         s) Seed=$OPTARG ;;
  38         *) usage ; exit 2;;
  39         esac
  40 done
  41
  42 shift $(($OPTIND - 1))
  43
  44 case $# in
  45         2) Lower=$1; Upper=$2 ;;
  46         *) usage ; exit 2;;
  47 esac
  48
  49 # Check that specified values are integers:
  50 expr "$Lower" + 0 >/dev/null 2>&1
  51 [ $? -eq 2 ] && { errexit "lower ($Lower) not an integer"; }
  52 expr "$Upper" + 0 >/dev/null 2>&1
  53 [ $? -eq 2 ] && { errexit "upper ($Upper) not an integer"; }
  54 expr "$Seed" + 0 >/dev/null 2>&1
  55 [ $? -eq 2 ] && { errexit "seed ($Seed) not an integer"; }
  56
  57 # Check that values are in the correct range:
  58 if (( "$Lower" < 0 )) || [ ${#Lower} -gt 5 ]; then
  59         errexit "lower limit ($Lower) less than zero"
  60 fi
  61 if (( "$Upper" > 32767 )) || [ ${#Upper} -gt 5 ]; then
  62         errexit "upper limit ($Upper) greater than 32767"
  63 fi
  64 if (( "$Seed" < 0 )) || (( "$Seed" > 32767 )) || [ ${#Seed} -gt 5 ]; then
  65         errexit "seed value ($Seed) out of range (0 to 32767)"
  66 fi
  67 (( "$Upper" <= "$Lower" )) && errexit "upper limit ($Upper) <= lower limit ($Lower)"
  68
  69 # Seed the random-number generator:
  70 RANDOM=$Seed
  71 # Compute value, scaled within range:
  72 let rand="$RANDOM % ($Upper - $Lower + 1) + $Lower"
  73 # Report result:
  74 echo $rand