Using the dynamic variable `%Random%`

, we can get a random integer from 0 to 32767. For example:

```
echo %random%
```

This obviously, returns an integer from 0 to 32767. But sometimes we want it to be in a specific range, say from 1 to 100.

The basic method to do so is listed below.

`set /a result=(%RANDOM%*`**max**/32768)+**min**

where `max`

is the top number that can be generated, and `min`

is the smallest number that can be generated. Note that you will not get any decimal numbers because `set /a`

rounds down automatically. To generate a decimal random number, try this:

`set /a whole=(%RANDOM%*`**max**/32768)+**min**
set /a decimal=(%RANDOM%***max**/32768)+**min**
echo %whole%.%decimal%

If you try

```
set /a whole=(%RANDOM%*65536/32768)+1
```

you will most likely get random numbers that are odd.

To generate numbers larger than 32767, here is a better method.

```
set /a result=%random:~-1%%random:~-1%%random:~-1%%random:~-1%%random:~-1%%random:~-1%
```

The previous code extracts the 1 character from each `%random%`

. But this is done on purpose.

Since the `random`

number could be one digit number, extracting the last 2 digit won't work. That's why we extract only the last character. In this case, we have 6 `%random:~-1%`

, generating the maximum of `999999`

, and the minimum at `000000`

, you may need to adjust this to suit your needs.

`cmd.exe`

generate the seed based on the time the `cmd`

section started, so if you start mutliple section at the nearly same time, the result may not be 'random' enough.

Unfortunately, batch does not have a built-in method to generate alphabets, but using `%random%`

and `for`

loop, we can 'generate' alphabets.

This is a simple idea of how this works.

```
set /a result=(%random%*26/32768)+1
for /f "tokens=%result%" %%I in ("A B C D E F G H I J K L M N O P Q R S T U V W X Y Z") do (
echo %%I
)
```

- The first
`set /a`

statement generate a random number`N`

between 1 to 26 - The
`for /f`

statement picks the`N`

th item from a list of A to Z.- Return the result

One can put a total `31`

items in 1 `for`

loop, and practically unlimited items using [this method].(Batch - for loop parameter order

Accorinding to this Stack Overflow answer, user CherryDT pointed out this code:

```
set /a num=%random% %% 100
```

does not give a uniform distribution.

The internal dynamic variable `%random%`

**does** gives a **uniform distribution**, but the above code will not be a uniformed random. This code generates a random number between 0 ~ 99, but the result will not be uniform. 0 ~ 67 will occur more than 68 ~ 99 since `32767 MOD 100`

= `67`

.

To generate a uniform distributed random using the above code, then `100`

must be changed. Here is a method to get a number that creates a uniform distribution.

```
32767 mod (32767 / n)
```

where `n`

is an integer, between 0 ~ 32767, the result may be decimal and may not work in batch.

```
set /a result=(%RANDOM%*100/32768)+1
```

This method will generate a uniform distribution. It avoids using `%`

, which is more like "remainder" then "modulus" in a batch script. Without using `%`

, the result will be uniform.

Alternatively, here is an inefficient, but uniform method.

```
set /a test=%random%
if %test% geq [yourMinNumber] (
if %test% leq [yourMaxNumber] (
rem do something with your random number that is in the range.
)
)
```

Change `[yourMinNumber]`

and `[yourMaxNumber]`

accordingly to your own values.

This modified text is an extract of the original Stack Overflow Documentation created by following contributors and released under CC BY-SA 3.0

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