TAR - USTAR Format
The 1988 POSIX format: 512-byte headers, octal numeric fields, names split across a 155-byte prefix and a 100-byte name, and no mechanism at all for anything that does not fit - including the access and change times its siblings carry. All three archives in this group hold byte-identical members with identical ownership and modification times, so any other difference a reader reports between them comes from the header encoding alone.
- README.txt
- main.txt
- records.csv
Specifications
- Seed
- 20260807
- Tar Format
- USTAR (POSIX.1-1988)
- Members
- 3
- Block Size
- 512
- Header Magic
- magic "ustar\0" + version "00"
- Extended Headers
- none
- Uid
- 1000
- Gid
- 1000
- Uname
- novus
- Gname
- novus
- Mtime
- 1767225600
- Twin
- identical member content and mtime/ownership in all three formats
Testing contract
Expected to pass- Scenario
- Extract all three format twins and compare the resulting trees and metadata.
- Expected result
- All three yield the same 3 files with mtime 1767225600, uid/gid 1000/1000 and owner names novus/novus; this one identifies itself by magic "ustar\0" + version "00".
What is a .tar file?
TAR (Tape Archive) is a Unix archive format that concatenates files with their metadata into a single uncompressed stream of fixed-size blocks. It preserves permissions, ownership, and directory structure but applies no compression itself. It is usually paired with a compressor such as gzip or xz.
How to use this file
Use an example TAR to test archive extraction, metadata and permission preservation, streaming block parsing, and pipelines that combine tar with external compression.
How to use this file for testing
“TAR - USTAR Format” is a deterministic Novus Examples fixture for Conversion testing, Metadata testing. The same content exported across many formats and linked as a group, so you can convert one and diff against the expected twin.
Documented properties for this file: seed 20260807. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Archive fixtures are documented down to their member list (shown on this page) and are deliberately safe — no zip bombs, executables, or hidden payloads. Test extractors against nested, unicode, empty, and encrypted variants.
Code examples
tar -tf tree-ustar.tar # list
tar -xf tree-ustar.tar -C out/ # extractRelated files
- txtConvert v2 Archive SHA-256 ListGNU-style SHA-256 list for the two canonical TAR members, preserving relative paths and full lowercase digests. Stable P8 artifact p8-convert-archive-sha256.
- jarJAR With a Nested Library JARThe nested-JAR layout an executable fat jar uses: a manifest with a Class-Path entry and a second JAR stored uncompressed under BOOT-INF/lib so it can be read in place without being extracted first. It contains resources only - properties, JSON and text, no compiled bytecode - and the manifest uses the CRLF line endings the JAR specification requires.
- tarTAR - Directory Members and an Empty DirectoryThree directory records with distinct modes, one of which - tree/empty/ - has no members underneath it and therefore exists only because the record does. A reader that synthesises directories from member paths alone silently loses it, and loses the 0750 and 0700 modes on the other two.
- tarTAR - FIFO and Device Node RecordsA FIFO, a character device and a block device, each a header with no data blocks and with the device numbers in the devmajor/devminor fields. Unprivileged extraction cannot create the two device nodes, so the correct behaviour is to skip them with a warning rather than to abort the whole archive or to create empty regular files in their place.
- tarTAR - Hard Link Membershare/backup/records.csv is a hard link to a member that appears earlier in the stream, so its content is stored exactly once. Order matters: a reader that extracts members out of sequence, or that copies content instead of linking, changes both the on-disk byte count and the inode relationship the archive is describing.
- tarTAR - Large UID/GID (GNU base-256)The uid and gid fields hold 7 octal digits, so they top out at 2097151. This member is owned by uid 3000000, which needs GNU base-256 encoding: the field's high bit is set and the remaining bytes are a big-endian integer. Its group sibling encodes the same ownership the other way, so a reader can be checked against both without a second variable.
Generated by generation/archives_p7.py. Free for any use, no attribution required — license.