# Copying UDF Values from Source to Destination

How to copy the value of a UDF/custom field from source to destination (typically from the inputs of a process/step to the outputs) is a frequently asked question.

For example, suppose a process/step takes in libraries and tracks their normalization. In such a case, the input samples have a UDF/custom field that is used to track the library ID. Since the library ID changes, it is desirable for the output samples to also have this ID.

### Solution

Use the API to gather the XML for the inputs, then copy the XML node relating to the UDF/custom field to the outputs.

Alternatively, use the out-of-the-box copyUDFs script, which Illumina provides as part of the NextGen Sequencing configuration.

### Script

The **copyUDFs** script is available in the **ngs-extensions.jar** archive\*, and can be called from the EPP / automation parameter string.

The archive file may be named differently, depending upon the version you are running.

Usage:

```
java -jar ngs-extensions.jar -u {username} -p {password} -i {processURI} \
script:copyUDFs -f <myUDF1>,<myUDF2>,<myUDF3>
```

#### Defining the UDF / custom field values

The UDF / custom field values to be copied are defined in the **-f** portion of the syntax. These values must be present on both the inputs and outputs of a process.

For example, suppose you wanted to use this script to copy the value of a UDF called **Library ID**:

* The **Library ID** field must be defined on both inputs and outputs.
* The **-f** flag is defined as follows:

  ```
  -f "Library ID"
  ```

To copy **multiple UDF values** from source to destination, list them in comma-separated form as part of the **-f** flag.

* To copy **Library ID** and **Organism** from source to destination, use the following example:

  ```
  -f "Library ID", "Organism"
  ```