compressFile: Compressing and decompressing files

Description

Compressing and decompressing files such as gzip:ed and bzip2:ed files.

NOTE: The default (remove=TRUE) behavior is that the input file is removed after that the output file is fully created and closed.

Usage

"compressFile"(filename, destname=sprintf("%s.%s", filename, ext), ext, FUN, temporary=FALSE, skip=FALSE, overwrite=FALSE, remove=TRUE, BFR.SIZE=1e+07, ...) "decompressFile"(filename, destname=gsub(sprintf("[.]%s$", ext), "", filename, ignore.case = TRUE), ext, FUN, temporary=FALSE, skip=FALSE, overwrite=FALSE, remove=TRUE, BFR.SIZE=1e+07, ...) "isCompressedFile"(filename, method=c("extension", "content"), ext, fileClass, ...) "bzip2"(filename, ..., ext="bz2", FUN=bzfile) "bunzip2"(filename, ..., ext="bz2", FUN=bzfile) "gzip"(filename, ..., ext="gz", FUN=gzfile) "gunzip"(filename, ..., ext="gz", FUN=gzfile)

Arguments

filename

Pathname of input file.

destname

Pathname of output file.

temporary

If TRUE, the output file is created in a temporary directory.

skip

If TRUE and the output file already exists, the output file is returned as is.

overwrite

If TRUE and the output file already exists, the file is silently overwritting, otherwise an exception is thrown (unless skip is TRUE).

remove

If TRUE, the input file is removed afterward, otherwise not.

BFR.SIZE

The number of bytes read in each chunk.

...

Passed to the underlying function or alternatively not used.

method

A character string specifying how to infer whether a file is compressed or not.

ext, fileClass, FUN

(internal) Filename extension, file class, and a connection function used to read from/write to file.

Value

Returns the pathname of the output file. The number of bytes processed is returned as an attribute.isCompressedFile() etc. return a logical.

Details

Internally bzfile() and gzfile() (see connections) are used to read (write) files. If the process is interrupted before completed, the partially written output file is automatically removed.

Examples

Run this code

  ## bzip2
  cat(file="foo.txt", "Hello world!")
  print(isBzipped("foo.txt"))
  print(isBzipped("foo.txt.bz2"))

  bzip2("foo.txt")
  print(file.info("foo.txt.bz2"))
  print(isBzipped("foo.txt"))
  print(isBzipped("foo.txt.bz2"))

  bunzip2("foo.txt.bz2")
  print(file.info("foo.txt"))

  ## gzip
  cat(file="foo.txt", "Hello world!")
  print(isGzipped("foo.txt"))
  print(isGzipped("foo.txt.gz"))

  gzip("foo.txt")
  print(file.info("foo.txt.gz"))
  print(isGzipped("foo.txt"))
  print(isGzipped("foo.txt.gz"))

  gunzip("foo.txt.gz")
  print(file.info("foo.txt"))

  ## Cleanup
  file.remove("foo.txt")