libarchive - functions for reading and writing streaming archives
Please see following description for synopsis
LIBARCHIVE(3lib) LIBARCHIVE(3lib)
NAME
libarchive - functions for reading and writing streaming archives
OVERVIEW
The libarchive library provides a flexible interface for reading and
writing archives in various formats such as tar and cpio. libarchive
also supports reading and writing archives compressed using various
compression filters such as gzip and bzip2. The library is inherently
stream-oriented; readers serially iterate through the archive, writers
serially add things to the archive. In particular, note that there is
currently no built-in support for random access nor for in-place modi-
fication.
When reading an archive, the library automatically detects the format
and the compression. The library currently has read support for:
o old-style tar archives,
o most variants of the POSIX ``ustar'' format,
o the POSIX ``pax interchange'' format,
o GNU-format tar archives,
o most common cpio archive formats,
o 7-Zip archives,
o ar archives (including GNU/SysV and BSD extensions),
o Microsoft CAB archives,
o ISO9660 CD images (including RockRidge and Joliet exten-
sions),
o LHA archives,
o mtree file tree descriptions,
o RAR and most RAR5 archives,
o WARC archives,
o XAR archives,
o Zip archives.
The library automatically detects archives compressed with compress(1),
bzip2(1), grzip(1), gzip(1), lrzip(1), lz4(1), lzip(1), lzop(1), xz(1),
or zstd(1) and decompresses them transparently. Decompression of some
formats requires external decompressor utilities. It can similarly
detect and decode archives processed with uuencode(1) or which have an
rpm(1) header.
When writing an archive, you can specify the compression to be used and
the format to use. The library can write
o POSIX-standard ``ustar'' archives,
o POSIX ``pax interchange format'' archives,
o cpio archives,
o 7-Zip archives,
o ar archives,
o two different variants of shar archives,
o ISO9660 CD images,
o mtree file tree descriptions,
o XAR archives,
o Zip archive.
Pax interchange format is an extension of the tar archive format that
eliminates essentially all of the limitations of historic tar formats
in a standard fashion that is supported by POSIX-compliant pax(1)
implementations on many systems as well as several newer implementa-
tions of tar(1). Note that the default write format will suppress the
pax extended attributes for most entries; explicitly requesting pax
format will enable those attributes for all entries.
The read and write APIs are accessed through the archive_read_XXX()
functions and the archive_write_XXX() functions, respectively, and
either can be used independently of the other.
The rest of this manual page provides an overview of the library opera-
tion. More detailed information can be found in the individual manual
pages for each API or utility function.
READING AN ARCHIVE
See archive_read(3).
WRITING AN ARCHIVE
See archive_write(3).
WRITING ENTRIES TO DISK
The archive_write_disk(3) API allows you to write archive_entry(3)
objects to disk using the same API used by archive_write(3). The ar-
chive_write_disk(3) API is used internally by archive_read_extract(;)
using it directly can provide greater control over how entries get
written to disk. This API also makes it possible to share code between
archive-to-archive copy and archive-to-disk extraction operations.
READING ENTRIES FROM DISK
The archive_read_disk(3) supports for populating archive_entry(3)
objects from information in the filesystem. This includes the informa-
tion accessible from the stat(2) system call as well as ACLs, extended
attributes, and other metadata. The archive_read_disk(3) API also sup-
ports iterating over directory trees, which allows directories of files
to be read using an API compatible with the archive_read(3) API.
DESCRIPTION
Detailed descriptions of each function are provided by the correspond-
ing manual pages.
All of the functions utilize an opaque Tn struct archive datatype that
provides access to the archive contents.
The Tn struct archive_entry structure contains a complete description
of a single archive entry. It uses an opaque interface that is fully
documented in archive_entry(3).
Users familiar with historic formats should be aware that the newer
variants have eliminated most restrictions on the length of textual
fields. Clients should not assume that filenames, link names, user
names, or group names are limited in length. In particular, pax inter-
change format can easily accommodate pathnames in arbitrary character
sets that exceed PATH_MAX.
RETURN VALUES
Most functions return ARCHIVE_OK (zero) on success, non-zero on error.
The return value indicates the general severity of the error, ranging
from ARCHIVE_WARN, which indicates a minor problem that should probably
be reported to the user, to ARCHIVE_FATAL, which indicates a serious
problem that will prevent any further operations on this archive. On
error, the archive_errno() function can be used to retrieve a numeric
error code (see errno(2)). The archive_error_string() returns a tex-
tual error message suitable for display.
archive_read_new() and archive_write_new() return pointers to an allo-
cated and initialized Tn struct archive object.
archive_read_data() and archive_write_data() return a count of the num-
ber of bytes actually read or written. A value of zero indicates the
end of the data for this entry. A negative value indicates an error,
in which case the archive_errno() and archive_error_string() functions
can be used to obtain more information.
ENVIRONMENT
There are character set conversions within the archive_entry(3) func-
tions that are impacted by the currently-selected locale.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------+
|Availability | library/libarchive |
+---------------+--------------------+
|Stability | Uncommitted |
+---------------+--------------------+
SEE ALSO
tar(1), archive_entry(3), archive_read(3), archive_util(3), ar-
chive_write(3)
HISTORY
The libarchive library first appeared in FreeBSD 5.3.
AUTHORS
-nosplit The libarchive library was originally written by Tim Kientzle
<kientzle@acm.org.>
BUGS
Some archive formats support information that is not supported by Tn
struct archive_entry. Such information cannot be fully archived or
restored using this library. This includes, for example, comments,
character sets, or the arbitrary key/value pairs that can appear in pax
interchange format archives.
Conversely, of course, not all of the information that can be stored in
an Tn struct archive_entry is supported by all formats. For example,
cpio formats do not support nanosecond timestamps; old tar formats do
not support large device numbers.
The ISO9660 reader cannot yet read all ISO9660 images; it should learn
how to seek.
The AR writer requires the client program to use two passes, unlike all
other libarchive writers.
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://github.com/libarchive/libarchive/releases/down-
load/v3.6.1/libarchive-3.6.1.tar.gz.
Further information about this software can be found on the open source
community website at http://www.libarchive.org/.
March 18, 2012 LIBARCHIVE(3lib)