pushTemporaryFile: Appends a temporary suffix to the pathname

In HenrikBengtsson/R.utils: Various Programming Utilities

Appends a temporary suffix to the pathname

Description

Appends a temporary suffix to the pathname and, optionally, renames an existing file accordingly.

In combination with popTemporaryFile(), this method is useful for creating a file/writing data to file atomically, by first writing to a temporary file which is the renamed. If for some reason the generation of the file was interrupted, for instance by a user interrupt or a power failure, then it is only the temporary file that is incomplete.

Usage

## Default S3 method:
pushTemporaryFile(filename, path=NULL, suffix=".tmp", isFile=FALSE, ..., verbose=FALSE)

Arguments

filename	The filename of the file.
path	The path of the file.
suffix	The suffix to be appended.
isFile	If TRUE, the file must exist and will be renamed on the file system. If FALSE, it is only the pathname string that will be modified. For details, see below.
...	Not used.
verbose	A logical or Verbose.

Details

If isFile is FALSE, the pathname where the suffix of the temporary pathname has been added is returned. If isFile is TRUE, the file is also renamed. Then, if the file does not exists or it was not successfully renamed, an exception is thrown.

Value

Returns the pathname with the suffix appended.

Author(s)

Henrik Bengtsson

See Also

popTemporaryFile().

Examples

createAtomically <- function(pathname, ...) {
  cat("Pathname: ", pathname, "\n", sep="");

  # Generate a file atomically, i.e. the file will either be
  # complete or not created at all.  If interrupted while
  # writing, only a temporary file will exist/remain.
  pathnameT <- pushTemporaryFile(pathname);
  cat("Temporary pathname: ", pathnameT, "\n", sep="");

  cat(file=pathnameT, "This file was created atomically:\n");
  for (kk in 1:10) {
    cat(file=pathnameT, kk, "\n", append=TRUE);
    # Emulate a slow process
    if (interactive()) Sys.sleep(0.1)
  }
  cat(file=pathnameT, "END OF FILE\n", append=TRUE);

  # Rename the temporary file
  pathname <- popTemporaryFile(pathnameT);

  pathname;
} # createAtomically()


pathname <- tempfile();

tryCatch({
  # Try to interrupt the process while writing...
  pathname <- createAtomically(pathname);
}, interrupt=function(intr) {
  str(intr);
})

# ...and this will throw an exception
bfr <- readLines(pathname);
cat(bfr, sep="\n");

HenrikBengtsson/R.utils documentation built on March 7, 2024, 9:37 a.m.