4mLIBARCHIVE24m(3) Library Functions Manual 4mLIBARCHIVE24m(3) 1mNAME0m libarchive — functions for reading and writing streaming archives 1mOVERVIEW0m The 1mlibarchive 22mlibrary provides a flexible interface for reading and writing archives in various formats such as tar and cpio. 1mlibarchive0m 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: 1m• 22mold-style tar archives, 1m• 22mmost variants of the POSIX “ustar” format, 1m• 22mthe POSIX “pax interchange” format, 1m• 22mGNU-format tar archives, 1m• 22mmost common cpio archive formats, 1m• 22m7-Zip archives, 1m• 22mar archives (including GNU/SysV and BSD extensions), 1m• 22mMicrosoft CAB archives, 1m• 22mISO9660 CD images (including RockRidge and Joliet extensions), 1m• 22mLHA archives, 1m• 22mmtree file tree descriptions, 1m• 22mRAR and most RAR5 archives, 1m• 22mWARC archives, 1m• 22mXAR archives, 1m• 22mZip archives. The library automatically detects archives compressed with 4mcompress24m(1), 4mbzip224m(1), 4mgrzip24m(1), 4mgzip24m(1), 4mlrzip24m(1), 4mlz424m(1), 4mlzip24m(1), 4mlzop24m(1), 4mxz24m(1), or 4mzstd24m(1) and decompresses them transparently. Decompression of some formats requires external decompressor utilities. It can similarly de‐ tect and decode archives processed with 4muuencode24m(1) or which have an 4mrpm24m(1) header. When writing an archive, you can specify the compression to be used and the format to use. The library can write 1m• 22mPOSIX-standard “ustar” archives, 1m• 22mPOSIX “pax interchange format” archives, 1m• 22mcpio archives, 1m• 22m7-Zip archives, 1m• 22mar archives, 1m• 22mtwo different variants of shar archives, 1m• 22mISO9660 CD images, 1m• 22mmtree file tree descriptions, 1m• 22mXAR archives, 1m• 22mZip 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 4mpax24m(1) im‐ plementations on many systems as well as several newer implementations of 4mtar24m(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 1marchive_read_XXX22m() functions and the 1marchive_write_XXX22m() functions, respectively, and ei‐ ther 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. 1mREADING AN ARCHIVE0m See 4marchive_read24m(3). 1mWRITING AN ARCHIVE0m See 4marchive_write24m(3). 1mWRITING ENTRIES TO DISK0m The 4marchive_write_disk24m(3) API allows you to write 4marchive_entry24m(3) ob‐ jects to disk using the same API used by 4marchive_write24m(3). The 4marchive_write_disk24m(3) API is used internally by 1marchive_read_extract22m(); 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. 1mREADING ENTRIES FROM DISK0m The 4marchive_read_disk24m(3) supports for populating 4marchive_entry24m(3) ob‐ jects from information in the filesystem. This includes the informa‐ tion accessible from the 4mstat24m(2) system call as well as ACLs, extended attributes, and other metadata. The 4marchive_read_disk24m(3) API also sup‐ ports iterating over directory trees, which allows directories of files to be read using an API compatible with the 4marchive_read24m(3) API. 1mDESCRIPTION0m Detailed descriptions of each function are provided by the correspond‐ ing manual pages. All of the functions utilize an opaque struct archive datatype that provides 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 4marchive_entry24m(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 4mPATH_MAX24m. 1mRETURN VALUES0m Most functions return 1mARCHIVE_OK 22m(zero) on success, non-zero on error. The return value indicates the general severity of the error, ranging from 1mARCHIVE_WARN22m, which indicates a minor problem that should probably be reported to the user, to 1mARCHIVE_FATAL22m, which indicates a serious problem that will prevent any further operations on this archive. On error, the 1marchive_errno22m() function can be used to retrieve a numeric error code (see 4merrno24m(2)). The 1marchive_error_string22m() returns a tex‐ tual error message suitable for display. 1marchive_read_new22m() and 1marchive_write_new22m() return pointers to an allo‐ cated and initialized struct archive object. 1marchive_read_data22m() and 1marchive_write_data22m() 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 1marchive_errno22m() and 1marchive_error_string22m() functions can be used to obtain more information. 1mENVIRONMENT0m There are character set conversions within the 4marchive_entry24m(3) func‐ tions that are impacted by the currently-selected locale. 1mSEE ALSO0m 4mtar24m(1), 4marchive_entry24m(3), 4marchive_read24m(3), 4marchive_util24m(3), 4marchive_write24m(3), 4mtar24m(5) 1mHISTORY0m The 1mlibarchive 22mlibrary first appeared in FreeBSD 5.3. 1mAUTHORS0m The 1mlibarchive 22mlibrary was originally written by Tim Kientzle . 1mBUGS0m Some archive formats support information that is not supported by struct archive_entry. Such information cannot be fully archived or re‐ stored using this library. This includes, for example, comments, char‐ acter sets, or the arbitrary key/value pairs that can appear in pax in‐ terchange 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 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. Debian March 18, 2012 4mLIBARCHIVE24m(3)