Extract or List Tar Archives
Extract files from or list a tar archive.
untar(tarfile, files = NULL, list = FALSE, exdir = ".", compressed = NA, extras = NULL, verbose = FALSE, restore_times = TRUE, tar = Sys.getenv("TAR"))
- The pathname of the tar file: tilde expansion (see
path.expand) will be performed. Alternatively, a connection that can be used for binary reads.
- A character vector of recorded filepaths to be extracted: the default is to extract all files.
TRUE, list the files (the equivalent of
tar -tf). Otherwise extract the files (the equivalent of
- The directory to extract files to (the equivalent of
tar -C). It will be created if necessary.
- logical or character. Values
"xz"select that form of compression (and may be abbreviated to the first letter).
TRUEindicates gzip compression,
FALSEno known compression (but an external
tarcommand may detect compression automagically), and
NA(the default) that the type is inferred from the file header.
NULLor a character string: further command-line flags such as -p to be passed to an external
- logical: if true echo the command used.
- logical. If true (default) restore file modification times. If false, the equivalent of the -m flag. Times in tarballs are supposed to be in UTC, but tarballs are submitted to CRAN with times in the future or far past: this argument allows such times to be discarded.
- character string: the path to the command to be used. If
the command itself contains spaces it needs to be quoted -- but
tarcan also contain flags separated from the command by spaces.
This is either a wrapper for a
tar command or for an
internal implementation written in R. The latter is used if
tarfile is a connection or if the argument
"" (except on Windows, when
tar.exe is tried first).
What options are supported will depend on the
Modern GNU flavours of
tar will support compressed archives,
and since 1.15 are able to detect the type of compression
automatically: version 1.20 added support for
version 1.22 for
xz compression using LZMA2. OS X 10.6 and
later (and FreeBSD and some other OSes) have a
bsdtar) from the libarchive project which
can also detect
automatically. For other flavours of
variable R_GZIPCMD gives the command to decompress
compress files, and
verbose are only
used when an external
tar is used.
The internal implementation restores symbolic links as links on a
Unix-alike, and as file copies on Windows (which works only for
existing files, not for directories), and hard links as links. If the
linking operation fails (as it may on a FAT file system), a file copy
is tried. Since it uses
gzfile to read a file it can
handle files compressed by any of the methods that function can
handle: at least
xz compression, and some types of
compression. It does not guard against restoring absolute file paths,
tar implementations do. It will create the parent
directories for directories or files in the archive if necessary. It
handles the standard (USTAR/POSIX), GNU and
pax ways of
handling file paths of more than 100 bytes, and the GNU way of
handling link targets of more than 100 bytes.
You may see warnings from the internal implementation such as
unsupported entry type 'x'This often indicates an invalid archive: entry types
"A-Z"are allowed as extensions, but other types are reserved. The only thing you can do with such an archive is to find a
tarprogram that handles it, and look carefully at the resulting files. There may also be the warning
using pax extended headersThis is indicates that additional information may have been discarded, such as ACLs, encodings ..., and long path and link names are only used as from R 2.15.3.
The standards only support ASCII filenames (indeed, only alphanumeric
plus period, underscore and hyphen).
untar makes no attempt to map
filenames to those acceptable on the current system, and treats the
filenames in the archive as applicable without any re-encoding in the
list = TRUE, a character vector of (relative or absolute) paths of files contained in the tar archive.Otherwise the return code from