Here's how to capture the call to a function - from within that function. And to get it into a string using deparse().

get_call.R

# source: http://r.789695.n4.nabble.com/get-arguments-passed-to-function-inside-a-function-td3783894.html

tmpfun2 <- function(x,y,z,...) {
( match.call() )
}

temp <- (tmpfun2(1,2,3))
temp <- deparse(temp)
class(temp)