Opening an ff file

open.ff opens an ff file, optionally marking it readonly and optionally specifying a caching scheme.

# S3 method for class 'ff'
open(con, readonly = FALSE, pagesize = NULL, caching = NULL, assert = FALSE, ...)
 # S3 method for class 'ffdf'
open(con, readonly = FALSE, pagesize = NULL, caching = NULL, assert = FALSE, ...)

Arguments

con

an ff or ffdf object

readonly

readonly

pagesize

number of bytes to use as pagesize or NULL to take the pagesize stored in the physical attribute of the ff object, see getalignedpagesize

caching

one of 'mmnoflush' or 'mmeachflush', see ff

assert

setting this to TRUE will give a message if the ff was not open already

...

further arguments (not used)

Details

ff objects will be opened automatically when accessing their content and the file is still closed. Opening ffdf objects will open all of their physical components including their row.names if they are is.ff

Value

TRUE if object could be opened, FALSE if it was opened already (or NA if not all components of an ffdf returned FALSE or TRUE on opening)

Author

Jens Oehlschlägel

See also

ff, close.ff, delete, deleteIfOpen, getalignedpagesize

Examples

  x <- ff(1:12)
  close(x)
#> [1] TRUE
  is.open(x)
#> [1] FALSE
  open(x)
#> [1] TRUE
  is.open(x)
#> [1] TRUE
  close(x)
#> [1] TRUE
  is.open(x)
#> [1] FALSE
  x[]
#> opening ff /tmp/Rtmph7o01n/ff/ff345fc02acd8f2.ff
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12
  is.open(x)
#> [1] TRUE
  y <- x
  close(y)
#> [1] TRUE
  is.open(x)
#> [1] FALSE
  rm(x,y); gc()
#>           used (Mb) gc trigger  (Mb) max used  (Mb)
#> Ncells 1162418 62.1    1994352 106.6  1994352 106.6
#> Vcells 2166506 16.6    8790397  67.1  8790397  67.1