bashrand

UNIX下SH的实现源码

#! /bin/bash
# bashrand - generate a random number in a specified range with an
#	     optionally specified ``seed'' value.
#
# Original Author: Peter Turnbull, May 1993

usage()
{
	echo "$PROG: usage: $PROG [-s seed] lower-limit upper-limit" >&2
}

PROG=${0##*/}

SEED=$$         # Initialize random-number seed value with PID

while getopts s: opt
do
	case "$opt" in
	s)	SEED=$OPTARG ;;
	*)	usage ; exit 2 ;;
	esac
done

shift $((OPTIND - 1))

# Process command-line arguments:
case $# in
    2)  Lower=$1; Upper=$2 ;;
    *)  usage ; exit 2 ;;
esac

# Check that specified values are integers:
expr "$Lower" + 0 >/dev/null 2>&1 || {
	echo "$PROG: lower ($Lower) not an integer" >&2
	exit 1
}

expr "$Upper" + 0 >/dev/null 2>&1 || {
	echo "$PROG: upper ($Upper) not an integer" >&2
	exit 1
}

expr "$SEED" + 0 >/dev/null 2>&1 || {
	echo "$PROG: seed ($SEED) not an integer" >&2
	exit 1
}

# Check that values are in the correct range:
(( $Lower < 0 )) || [ `expr "$Lower" : '.*'` -gt 5 ] && {
	echo "$PROG: Lower limit ($Lower) out of range" >&2
	exit 1
}

(( $Upper > 32767 )) || [ `expr "$Upper" : '.*'` -gt 5 ] && {
	echo "$PROG: Upper limit ($Upper) out of range" >&2;
	exit 1
}

(( $SEED < 0 )) || (( $SEED > 32767 )) || [ `expr "$SEED" : '.*'` -gt 5 ] && {
	echo "$PROG: Seed value ($SEED) out of range (0 to 32767)" >&2
	exit 1
}

(( $Upper <= $Lower )) && {
	echo "$PROG: upper ($Upper) <= lower value ($Lower)" >&2
	exit 1
}

# Seed the random-number generator:
RANDOM=$SEED

# Compute value, scaled within range:
let rand="$RANDOM % ($Upper - $Lower + 1) + $Lower"

# Report result:
echo $rand