LIBARCHIVE(3)		 BSD Library Functions Manual		 LIBARCHIVE(3)

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 com‐

     pression 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 modifi‐

     cation.

     When reading an archive, the library automatically detects the format and

     the compression.  The library currently has read support for:

     ·	 old-style tar archives,

     ·	 most variants of the POSIX “ustar” format,

     ·	 the POSIX “pax interchange” format,

     ·	 GNU-format tar archives,

     ·	 most common cpio archive formats,

     ·	 ISO9660 CD images (including RockRidge and Joliet extensions),

     ·	 Zip archives,

     ·	 ar archives (including GNU/SysV and BSD extensions),

     ·	 Microsoft CAB archives,

     ·	 LHA archives,

     ·	 mtree file tree descriptions,

     ·	 RAR archives,

     ·	 XAR archives.

     The library automatically detects archives compressed with gzip(1),

     bzip2(1), xz(1), lzip(1), or compress(1) and decompresses them transpar‐

     ently.  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

     ·	 POSIX-standard “ustar” archives,

     ·	 POSIX “pax interchange format” archives,

     ·	 POSIX octet-oriented cpio archives,

     ·	 Zip archive,

     ·	 two different variants of shar archives,

     ·	 ISO9660 CD images,

     ·	 7-Zip archives,

     ·	 ar archives,

     ·	 mtree file tree descriptions,

     ·	 XAR archives.

     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) implemen‐

     tations on many systems as well as several newer implementations 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() func‐

     tions 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

     archive_write_disk(3) API is used internally by archive_read_extract();

     using it directly can provide greater control over how entries get writ‐

     ten to disk.  This API also makes it possible to share code between ar‐

     chive-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 information acces‐

     sible from the stat(2) system call as well as ACLs, extended attributes,

     and other metadata.  The archive_read_disk(3) API also supports 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 corresponding

     manual pages.

     All of the functions utilize an opaque struct archive datatype that pro‐

     vides access to the archive contents.

     The struct archive_entry structure contains a complete description of a

     single archive entry.  It uses an opaque interface that is fully docu‐

     mented in archive_entry(3).

     Users familiar with historic formats should be aware that the newer vari‐

     ants 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 interchange 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 textual

     error message suitable for display.

     archive_read_new() and archive_write_new() return pointers to an allo‐

     cated and initialized struct archive object.

     archive_read_data() and archive_write_data() return a count of the number

     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) functions

     that are impacted by the currently-selected locale.

SEE ALSO

     tar(1), archive_entry(3), archive_read(3), archive_util(3),

     archive_write(3), tar(5)

HISTORY

     The libarchive library first appeared in FreeBSD 5.3.

AUTHORS

     The libarchive library was originally written by Tim Kientzle

     <kientzle@acm.org>.

BUGS

     Some archive formats support information that is not supported by 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 struct archive_entry is supported by all formats.  For example, cpio

     formats do not support nanosecond timestamps; old tar formats do not sup‐

     port 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.

BSD				March 18, 2012				   BSD