Groovy script that count the number of lines in a files in my process

Hi everyone ,

im trying to count the number of lines in a document in my process . My script is :
//////////////////////////////////////////////////////////////////////////////////
def lines = 0
doc_Integrateur_Enseignes_CSV.eachLine {
lines++
}

////////////////////////////////////////////////////////////////////////////////

doc_Integrateur_Enseignes_CSV is the name of the document in my process ( i upload that document in the task that is prior to the task that contains the script ).
when i try to run the process ,when i submit the form that contains the script i have a screen with error while submiting the form written on it. Im working with bonita 6.5. Any idea everyone ? Thank you