How to check a file is opened or closed in R

Question

I would like to ask how can I check a file's status (whether it is opened or closed) before reading in R programming?

I have tried myfile = open(filenames); it doesn't work.

Answer 1

I think the trick is to use open = "w" to open for writing. This seems to work perfectly for me:

file.opened <- function(path) {
  suppressWarnings(
    "try-error" %in% class(
      try(file(path, 
               open = "w"), 
          silent = TRUE
      )
    )
  )
}

After I open an Excel file:

file.opened("C:\\Folder\\tbl1.xlsx")
# TRUE

And when I close it:

file.opened("C:\\Folder\\tbl1.xlsx")
# FALSE

Answer 2

Based on the answer by MS Berends, with modifications:

• Check the file actually exists, otherwise it look like non-existent files are open
• Access the file in r+ mode instead of w, because the latter sometimes does weird overwriting
• Close the file connection, so it doesn't give you a warning message when it automatically closes it for you later

is_file_open <- function(path) {
  # Make sure the file actually exists
  assertthat::assert_that(file.exists(path))

  # Try to open a connection to the file. Will fail if it's open
  attempted_connection <- suppressWarnings(
    try(file(path, open = "r+"), silent = TRUE)
  )

  # If the attempted connection gave an error, the file is probably open
  is_open <- inherits(attempted_connection, "try-error")

  # Good practice: close the connection if we did manage to open it
  if (!is_open) {
    close(attempted_connection)
  }

  return(is_open)
}