# Use `GenerateRandom` with an Amazon SDK or CLI
<a name="example_kms_GenerateRandom_section"></a>

The following code examples show how to use `GenerateRandom`.

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#### [ CLI ]

**Amazon CLI**  
**Example 1: To generate a 256-bit random byte string (Linux or macOs)**  
The following `generate-random` example generates a 256-bit (32-byte), base64-encoded random byte string. The example decodes the byte string and saves it in the random file.  
When you run this command, you must use the `number-of-bytes` parameter to specify the length of the random value in bytes.  
You don't specify a KMS key when you run this command. The random byte string is unrelated to any KMS key.  
By default, Amazon KMS generates the random number. However, if you specify a [custom key store](https://docs.aws.amazon.com/kms/latest/developerguide/keystore-cloudhsm.html), the random byte string is generated in the Amazon CloudHSM cluster associated with the custom key store.  
This example uses the following parameters and values:  
It uses the required `--number-of-bytes` parameter with a value of `32` to request a 32-byte (256-bit) string.It uses the `--output` parameter with a value of `text` to direct the Amazon CLI to return the output as text, instead of JSON.It uses the `--query parameter` to extract the value of the `Plaintext` property from the response.It pipes ( \| ) the output of the command to the `base64` utility, which decodes the extracted output.It uses the redirection operator ( > ) to save decoded byte string to the `ExampleRandom` file.It uses the redirection operator ( > ) to save the binary ciphertext to a file.  

```
aws kms generate-random \
    --number-of-bytes 32 \
    --output text \
    --query Plaintext | base64 --decode > ExampleRandom
```
This command produces no output.  
For more information, see [Amazon KMS cryptography essentials](https://docs.aws.amazon.com/kms/latest/developerguide/kms-cryptography.html#entropy-and-random-numbers) in the *Amazon Key Management Service Developer Guide*.  
**Example 2: To generate a 256-bit random number (Windows Command Prompt)**  
The following `generate-random` example generates a 256-bit (32-byte), base64-encoded random byte string. The example decodes the byte string and saves it in the random file. This example is the same as the previous example, except that it uses the `certutil` utility in Windows to base64-decode the random byte string before saving it in a file.  
First, generate a base64-encoded random byte string and saves it in a temporary file, `ExampleRandom.base64`.  

```
aws kms generate-random \
    --number-of-bytes {{32}} \
    --output {{text}} \
    --query {{Plaintext}} {{>}} {{ExampleRandom.base64}}
```
This command produces no output. The output of the `generate-random` command is saved in a file.  
Now use the `certutil -decode` command to decode the base64-encoded byte string in the `ExampleRandom.base64` file. Then, it saves the decoded byte string in the `ExampleRandom` file.  

```
certutil -decode ExampleRandom.base64 ExampleRandom
```
Output:  

```
Input Length = 18
Output Length = 12
CertUtil: -decode command completed successfully.
```
For more information, see [Amazon KMS cryptography essentials](https://docs.aws.amazon.com/kms/latest/developerguide/kms-cryptography.html#entropy-and-random-numbers) in the *Amazon Key Management Service Developer Guide*.  
+  For API details, see [GenerateRandom](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/kms/generate-random.html) in *Amazon CLI Command Reference*. 

------
#### [ Rust ]

**SDK for Rust**  
 There's more on GitHub. Find the complete example and learn how to set up and run in the [Amazon Code Examples Repository](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/rustv1/examples/kms#code-examples). 

```
async fn make_string(client: &Client, length: i32) -> Result<(), Error> {
    let resp = client
        .generate_random()
        .number_of_bytes(length)
        .send()
        .await?;

    // Did we get an encrypted blob?
    let blob = resp.plaintext.expect("Could not get encrypted text");
    let bytes = blob.as_ref();

    let s = base64::encode(bytes);

    println!();
    println!("Data key:");
    println!("{}", s);

    Ok(())
}
```
+  For API details, see [GenerateRandom](https://docs.rs/aws-sdk-kms/latest/aws_sdk_kms/client/struct.Client.html#method.generate_random) in *Amazon SDK for Rust API reference*. 

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For a complete list of Amazon SDK developer guides and code examples, see [Using this service with an Amazon SDK](sdk-general-information-section.md). This topic also includes information about getting started and details about previous SDK versions.