R help - Aug 2013 - How is a file descriptor stored ?

Hi,
        I thought that 'R' like java will allow me to store file names
(keys) and file descriptors(values) in a hashmap.


filelist.array <- function(n){
  sink("nmon.log")
  cpufile <- new.env(hash=T, parent=emptyenv())
  for (i in 1:n) {
    key <- paste("output", i, ".txt", sep = "")
    assign(key, file( key, "w" ), cpufile)
  }
    sink()
   return (cpufile)
}

But when I try to test it like this there is an exception

[1] "Exception is  Error in UseMethod(\"close\"): no applicable
method for
'close' applied to an object of class \"c('integer',
'numeric')\"\n"

test.simple.filelist.array <- function() {

    execution <- tryCatch({
		sink("nmon.log")
		listoffiles <- filelist.array(3)
		for (v in ls(listoffiles)) {
			print(paste("Map value is [", listoffiles[[v]], "]"))
			fd <- listoffiles[[v]]
			close(fd)
		}
        sink()
	}, error = function(err){
		print(paste("Exception is ",err))
	})
}

I think I am missing some fundamentals.

Thanks,
Mohan






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On 07-08-2013, at 12:13, mohan.radhakrishnan at polarisft.com wrote:
> 
> Hi,
>        I thought that 'R' like java will allow me to store file
names
> (keys) and file descriptors(values) in a hashmap.
> 
> 
> filelist.array <- function(n){
>  sink("nmon.log")
>  cpufile <- new.env(hash=T, parent=emptyenv())
>  for (i in 1:n) {
>    key <- paste("output", i, ".txt", sep =
"")
>    assign(key, file( key, "w" ), cpufile)
>  }
>    sink()
>   return (cpufile)
> }
> 
> But when I try to test it like this there is an exception
> 
> [1] "Exception is  Error in UseMethod(\"close\"): no
applicable method for
> 'close' applied to an object of class \"c('integer',
'numeric')\"\n"
> 
> test.simple.filelist.array <- function() {
> 
>    execution <- tryCatch({
> 		sink("nmon.log")
> 		listoffiles <- filelist.array(3)
> 		for (v in ls(listoffiles)) {
> 			print(paste("Map value is [", listoffiles[[v]],
"]"))
> 			fd <- listoffiles[[v]]
> 			close(fd)
> 		}
>        sink()
> 	}, error = function(err){
> 		print(paste("Exception is ",err))
> 	})
> }
> 
> I think I am missing some fundamentals.
> 
Read the help page for assign more carefully.
Use

assign(key, file( key, "w" ), envir=cpufile)

In your assign expression you are assigning cpufile to the third formal argument
which is pos.
You meant the envir argument, I presume.

Berend

I don't know how many files you are planning to open, but what you  
also might run into is the maximum number of connections namely 125.  
See ?file.

Jan



mohan.radhakrishnan at polarisft.com schreef:
> Hi,
>         I thought that 'R' like java will allow me to store file
names
> (keys) and file descriptors(values) in a hashmap.
>
>
> filelist.array <- function(n){
>   sink("nmon.log")
>   cpufile <- new.env(hash=T, parent=emptyenv())
>   for (i in 1:n) {
>     key <- paste("output", i, ".txt", sep =
"")
>     assign(key, file( key, "w" ), cpufile)
>   }
>     sink()
>    return (cpufile)
> }
>
> But when I try to test it like this there is an exception
>
> [1] "Exception is  Error in UseMethod(\"close\"): no
applicable method for
> 'close' applied to an object of class \"c('integer',
'numeric')\"\n"
>
> test.simple.filelist.array <- function() {
>
>     execution <- tryCatch({
> 		sink("nmon.log")
> 		listoffiles <- filelist.array(3)
> 		for (v in ls(listoffiles)) {
> 			print(paste("Map value is [", listoffiles[[v]],
"]"))
> 			fd <- listoffiles[[v]]
> 			close(fd)
> 		}
>         sink()
> 	}, error = function(err){
> 		print(paste("Exception is ",err))
> 	})
> }
>
> I think I am missing some fundamentals.
>
> Thanks,
> Mohan
>
>
>
>
>
>
> This e-Mail may contain proprietary and confidential information and  
> is sent for the intended recipient(s) only.  If by an addressing or  
> transmission error this mail has been misdirected to you, you are  
> requested to delete this mail immediately. You are also hereby  
> notified that any use, any form of reproduction, dissemination,  
> copying, disclosure, modification, distribution and/or publication  
> of this e-mail message, contents or its attachment other than by its  
> intended recipient/s is strictly prohibited.
>
> Visit us at http://www.polarisFT.com
>
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