str() method for FBMs

[privefl]

The problem

library(bigstatsr)
X <- big_attachExtdata()
X$backingfile
str(X)
Sys.chmod(X$backingfile, mode = "0444")
str(X)
X$is_read_only <- TRUE
str(X)

---

One starting point:

str.FBM <- function(object, ...) {
  cat("An object of class", class(object), "\n")
  cat(" - Dimensions:", paste(dim(object), collapse = " x "), "\n")
  cat(" - Backing file:", object$backingfile, "\n")
  cat(" - Writable:", if (file.access(object$backingfile, 2) == 0) "Yes" else "No", "\n")
}

PS; Should make look at is_read_only and file.access.