Editing Tar (computing) (section)

===POSIX.1-2001/pax===
In 1997, [[Sun Microsystems|Sun]] proposed a method for adding extensions to the tar format. This method was later accepted for the POSIX.1-2001 standard. This format is known as ''extended tar'' format or [[pax (command)|pax]] format. The new tar format allows users to add any type of vendor-tagged vendor-specific enhancements. The following tags are defined by the POSIX standard:
* '''atime''', '''mtime''': all timestamps of a file in arbitrary resolution (most implementations use nanosecond granularity)
* '''path''': path names of unlimited length and character set coding
* '''linkpath''': symlink target names of unlimited length and character set coding
* '''uname''', '''gname''': user and group names of unlimited length and character set coding
* '''size''': files with unlimited size (the historic tar format is 8 GB)
* '''uid''', '''gid''': userid and groupid without size limitation (the historic tar format is limited to a max. id of 2097151)
* a character set definition for path names and user/group names ([[UTF-8]])

In 2001, the Star program became the first tar to support the new format.{{cn|date=October 2021}} In 2004, GNU tar supported the new format,<ref>[https://git.savannah.gnu.org/cgit/tar.git/tree/NEWS NEWS], git.savannah.gnu.org - search for "Added support for POSIX.1-2001 and ustar archive formats."</ref> though it does not write it as its default output from the tar program yet.<ref name="gnu.org2">{{Cite web | url=https://www.gnu.org/software/tar/manual/html_section/Formats.html |title = GNU tar 1.34: 8. Controlling the Archive Format | website = GNU | access-date = 2022-07-11}}</ref>

The pax format is designed so that all implementations able to read the UStar format will be able to read the pax format as well. The only exceptions are files that make use of extended features, such as longer file names. For compatibility, these are encoded in the tar files as special {{code|x}} or {{code|g}} type files, typically under a {{code|PaxHeaders.XXXX}} directory.<ref>{{man|1|pax|SUS}}</ref>{{rp|exthdr.name}} A pax-supporting implementation would make use of the information, while non-supporting ones like [[7-Zip]] would process them as additional files.<ref>{{cite web |title=#2116 Tars with pax headers not parsed |url=https://sourceforge.net/p/sevenzip/bugs/2116/ |website=7-Zip / Bugs {{!}} SourceForge}}</ref>