Getting process ID and running `top` from R

sys_top.R

#' Run the Linux top command
#' 
#' @param user character value indicating a system user to filter tasks by
#' @param pid one or more process ids to retrieve
#' 
#' @return
#' A data.frame value containing the information returned by top.
#'
sys.top <- function(user=Sys.getenv("USER"),pid=NULL){
  # Run top in batch mode "-b" once "-n 1"
  top_cmd <- paste("top -b -n 1",
                   if(!is.null(user))paste("-U",user),
                   if(!is.null(pid))paste("-p",paste(pid,collapse=" ")))
  top_out <- system(top_cmd, intern=TRUE )
  # Drop the summary data from the results
  top_data <- top_out[-(1:7)]
  # Grab the field names, dropping the first empty value
  top_names <- strsplit(top_out[7],"[[:space:]]+")[[1]][-1]
  top_data <- top_data[nchar(top_data) > 0]
  # fields are space delimited
  top_data <- strsplit(top_data,"[[:space:]]+")
  top_ncols <- length(top_names)
  # Drop any empty rows at the bottom
  top_data <- lapply(top_data,
                     function(x)x[nchar(x)>0])
  # paste back together any "Command" values that we split up
  top_data <- lapply(top_data,function(x)c(x[1:(top_ncols-1)],
                                          paste(x[top_ncols:length(x)],collapse=" ")))
  top_df <- as.data.frame(do.call(rbind,top_data))
  names(top_df) <- top_names
  top_df
}

#' Get the Process ID (PID) for the R session
sys.pid <- function(){
  system("echo $PPID", intern=TRUE)
}