How to find out exception line number in R

Question

I am new to R language. I gone through exception handling frame work tutorials, but i can't able to find any options to print entire error stack trace , below is my code

getData<-function(a,b){
 c=NULL
 tryCatch({
     c=a+b
   },error=function(cond){
     fileConn<-file("output.txt")
     writeLines(as.character(cond), fileConn)
     close(fileConn)
   }
 )
 return(c)
}

In above code if any exception happens i need to write in a file by mentioning the line number where the error occurred, let's say i am getting input to the method like below

getData(1,"vv")

It will throw exception like below, but I am not able to find the exact line number where error occurred , please help me to resolve this issue

Error in a + b: non-numeric argument to binary operator