Opening an ff file

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

Usage

# 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

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/RtmpJwybJa/ff/ffad39a107b61.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 1252392 66.9    2239654 119.7  2239654 119.7
#> Vcells 2306545 17.6    8388608  64.0  8387257  64.0