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kor

StringRegExpReplace help

12 posts in this topic

$sMAC = "333311116666"

If StringRegExp($sMAC, "[0-9]") Then $sMac = StringRegExpReplace($sMAC, "[0-8]", "A", Random(1, 12))
ConsoleWrite($sMAC & @CR)

Trying to accomplish the following.

If $sMAC contains only digits between 0-9 then replace a random number of those digits with the following characters A through F.

I'm not sure how to accomplish the last bit. How do I have it choose a different letter for each replacement based on a pattern of available letters A through F?

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Are you trying to create a random MAC address? I'm pretty sure the site owner would not find that acceptable.

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#3 ·  Posted (edited)

$sMAC = "333311116666"
$max = stringlen ($sMAC)
If StringRegExp($sMAC, "[0-9]") Then
for $i = 1 to random(1, $max , 1)
$sMAC = stringreplace($sMAC , random(1, $max , 1) , Chr(Random(Asc("A"), Asc("F"), 1)))
next
Endif

ConsoleWrite($sMAC & @CR)

*fixed should match behavior described

Edited by boththose

,-. .--. ________ .-. .-. ,---. ,-. .-. .-. .-.
|(| / /\ \ |\ /| |__ __||| | | || .-' | |/ / \ \_/ )/
(_) / /__\ \ |(\ / | )| | | `-' | | `-. | | / __ \ (_)
| | | __ | (_)\/ | (_) | | .-. | | .-' | | \ |__| ) (
| | | | |)| | \ / | | | | | |)| | `--. | |) \ | |
`-' |_| (_) | |\/| | `-' /( (_)/( __.' |((_)-' /(_|
'-' '-' (__) (__) (_) (__)

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Are you trying to create a random MAC address? I'm pretty sure the site owner would not find that acceptable.

Yes.

We name our computers according to their MAC address when imaging. However some MAC's contain only numbers which is against MS best practices when naming computers.

Thus I am trying to randomize the MAC/Computer name so we don't get duplicates during imaging and follow MS best practices.

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#5 ·  Posted (edited)

We name our computers according to their MAC address when imaging. However some MAC's contain only numbers which is against MS best practices when naming computers.

Thus I am trying to randomize the MAC/Computer name so we don't get duplicates during imaging and follow MS best practices.

Ah! I got the wrong impression for a moment. I thought you were up to no good. I apologies for that.

I have always found avoiding duplicates when using random selection to be complicated. There are many possible permutations. Perhaps you could stick to only using values within a certain range or select a random smaller set from several ranges as candidates. No matter what you do, you will have to test the random addresses against those which don't need to be changed - unless you change them all. Making the numbers smaller is one way to simplify the problem. I need to think about this.

Edit

I calculate 280474976710657 permutations with a minimum of one letter in each 12 character address (unless I made a mistake).

Edited by czardas

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#6 ·  Posted (edited)

$sMAC = "333311116666"
$max = stringlen ($sMAC)
If StringRegExp($sMAC, "[0-9]") Then
for $i = 1 to random(1, $max , 1)
$sMAC = stringreplace($sMAC , random(1, $max , 1) , Chr(Random(Asc("A"), Asc("F"), 1)))
next
Endif

ConsoleWrite($sMAC & @CR)

*fixed should match behavior described

Thank you this works. wonder how I can tweak it. I'm reading about stringreplace and it has an optional flag of "occurrence" which I'm trying to set. I'd like to only replace 8 out of the maximum 12 digits, but only the last 8... never the first 4. Thus I was trying to make an occurrence of "-8" which by the helpdoc should start the checking from the right side, but it's not working like it should.

EDIT: got it. instead of using occurrence I just set the Random start searchstring to 5, 12, 1. Thanks!

Edited by kor

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#7 ·  Posted (edited)

Here another way:

Global $sMAC_New
$sMAC = "333311116666"
$aArr = StringSplit($sMAC, "", 2)
For $i = 0 To UBound($aArr) - 1
    If StringIsInt($aArr[$i]) Then $aArr[$i] = Chr(Random(65, 70, 1))
    $sMAC_New &= $aArr[$i]
Next
MsgBox(0, "Test", $sMAC_New)

Or:

Global $sMAC_New
$sMAC = "12345678"
For $i = 1 To StringLen($sMAC)
    If StringIsInt(StringMid($sMAC, $i, 1)) Then
        $sMAC_New &= Chr(Random(65, 70, 1))
    Else
        $sMAC_New &= StringMid($sMAC, $i, 1)
    EndIf
Next
MsgBox(0, "Test", $sMAC_New)

Br,

UEZ

Edited by UEZ

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In the OP you say each replacement must be different. I presume by that you mean that the same letter may not appear twice in the last 8 characters.

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#9 ·  Posted (edited)

Another approach: pseudo-randomize all MAC addresses since they mean nothing to you, but create them in sequence.

If you want to satisfy the requirement that MAC addresses have at least one hex digit yet be unique, use the following pseudocode:

Global $StationNumber = 12345  ; start with some non-negative value less than 2^63-1 - Round(((<expected number of stations> + 4) / 5) * 16)
Local $MAC
For <every station>
If Mod($StationNumber, 16) = 0 Then $StationNumber += 10
$MAC = Hex($StationNumber, 12) ; 12 digits in string, but last one (right) is in A-F
$StationNumber += 1 ; increment for next station
Next

Note: I choose to make the last hex digit in A-F, but you can easily adapt the idea to any other digit.

Edited by jchd

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PCRE v8.33 regexp documentation latest available release and currently implemented in AutoIt beta.

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SQLite official website with full documentation (may be newer than the SQLite library that comes standard with AutoIt)

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In the OP you say each replacement must be different. I presume by that you mean that the same letter may not appear twice in the last 8 characters.

No, you can repeat. That is the reason for the attempt at randomness in the replacements. That is also why I don't want to replace all the digits, just the last 8. This is a special case since not a lot of MAC address have only numbers, but my script must account for those rare machines.

I figure the percentage of MACs that contain only digits is low. Then add to that a randomized replacement of A-F on a randomized number of 1-8 digits should reduce the possability of a duplicate down to something so small it's not a worry.

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Posted Image

,-. .--. ________ .-. .-. ,---. ,-. .-. .-. .-.
|(| / /\ \ |\ /| |__ __||| | | || .-' | |/ / \ \_/ )/
(_) / /__\ \ |(\ / | )| | | `-' | | `-. | | / __ \ (_)
| | | __ | (_)\/ | (_) | | .-. | | .-' | | \ |__| ) (
| | | | |)| | \ / | | | | | |)| | `--. | |) \ | |
`-' |_| (_) | |\/| | `-' /( (_)/( __.' |((_)-' /(_|
'-' '-' (__) (__) (_) (__)

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#12 ·  Posted (edited)

No, you can repeat.

It was the following statement that threw me.

How do I have it choose a different letter for each replacement based on a pattern of available letters A through F?

I figure the percentage of MACs that contain only digits is low. Then add to that a randomized replacement of A-F on a randomized number of 1-8 digits should reduce the possability of a duplicate down to something so small it's not a worry.

Hmm, that's not water-tight. The chance of a repeat is also affected by the distribution of digits prior to replacement. If you think it's an acceptable risk, then okay. Edited by czardas

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