A file output can be used to take the data in a file and send it to an output port of the service.
Each call of a tool service works within its own specially created sub-directory of a directory specified by the location. When data is read from a file, the file is within the sub-directory for that call.
The command is zip archive.zip fred
This example shows that data contained within the file archive.zip will be output from the tool service on an output port called zipped_file. The Use port name for file box can be left ticked (the default) if you want the port name to be the same as that of the file.
The File type can affect how the tool service works. It is normally a bad idea to output binary data stored in a file as text data.
You can remove a file output by clicking the Remove button to the lower right of its area. This will remove both the output port and any reading from the corresponding file.
You can add a new file output by clicking the Add file output button. You will probably want to change the name of the port.