CFLib.org – Common Function Library Project

Description:
This UDF returns a string representation of a random number containing length digits. The function uses a combination of a UUID and the current date/time to periodically seed the ColdFusion random number generator.

Return Values:
Returns a number.

Example:

<cfoutput>
   Random Number is: #getRandomNumber(10)#<br>
</cfoutput>

Parameters:

Full UDF Source:

/**
 * This UDF returns a random number of a length passed in by the user.
 * Updates by original author with help from Steven Van Gemert.
 * 
 * @param length      Length of number. (Required)
 * @return Returns a number. 
 * @author Christopher Jordan (cjordan@placs.net) 
 * @version 2, May 12, 2006 
 */
function GetRandomNumber(length) {
    var i                 = "";
    var Seed              = "";
    var RandomNumber      = "";
    var ThisPart          = "";
    var TheTimeNow        = CreateODBCTime(Now());
    // change these values if you like
    var ThisStartTime     = CreateDateTime( Year(Now()), Month(Now()), Day(Now()), "09", "30", "00" );
    var ThisStopTime      = CreateDateTime( Year(Now()), Month(Now()), Day(Now()), "10", "00", "00" );
      
    // reseed only once every week between the specified start and stop times. In this case, if it's a tuesday between 9:30 and 10:00 in the morning.
    if(DayOfWeek(Now()) EQ 3 AND (TheTimeNow GTE ThisStartTime AND TheTimeNow LTE ThisStopTime)){
        // use just the numeric portions (or at least the last nine digits) of a UUID as a "random" seed
        Seed = Right(ReReplaceNoCase(CreateUUID(),"[A-F,\-]","","ALL"),9);
        Randomize(Seed);
    }

    // The use of NumberFormat in the following while loop assures the possiblity of having numbers which contain multiple consecutive zeros
    while (length){
        if(length GT 8){
            ThisPart = RandRange(0,99999999);
            ThisPart = NumberFormat(ThisPart,RepeatString("0",8));
            RandomNumber = RandomNumber & ThisPart;
            length = length - Len(ThisPart);
        } else {
            ThisPart = RandRange(0,RepeatString("9",length));
            ThisPart = NumberFormat(ThisPart,RepeatString("0",length));
            RandomNumber = RandomNumber & ThisPart;
            length = length - Len(ThisPart);
        }
    }
    return RandomNumber;
}