Determining File Type: Identifying POSIX Tar Archives

Abstract: When running the 'file' command on a file, the output indicates that the file is a POSIX tar archive (GNU). This article explains how to identify and confirm the file type using hex dump and Wikipedia resources.

Created: 2024-09-05 by UserComp.com Editors

Determining File Type: Identifying POSIX Tar Archives

In the world of computing, identifying file types is an essential task for managing and organizing files. One common file type is the POSIX Tar archive, often used for packaging and compressing files in Unix-like operating systems. This article will explore the key concepts and methods for identifying POSIX Tar archives.

What is a POSIX Tar Archive?

A POSIX Tar archive, also known as a tarball, is a file format used for packaging and compressing multiple files into a single archive. The name "tar" comes from the Unix command "tar," which stands for "tape archive." Tar archives are often used for distributing software, backing up files, and transferring files between systems.

Identifying POSIX Tar Archives

There are several ways to identify POSIX Tar archives, including using file command, hexdump, and file signatures. The following sections will explore each method in detail.

Using the File Command

The file command is a standard Unix utility that can determine the type of a file by analyzing its contents. To use the file command to identify a POSIX Tar archive, simply run the command followed by the file name:

$ file myfile.tar

If the file is a POSIX Tar archive, the output will be similar to the following:

myfile.tar: POSIX tar archive (GNU)

Using Hexdump

A hexdump is a command-line utility that displays the contents of a file in hexadecimal format. To identify a POSIX Tar archive using hexdump, you can look for the file signature "ustar" at the beginning of the file. The following is an example of a hexdump of a POSIX Tar archive:

$ hexdump -C myfile.tar

00000000  1f 8b 08 00 00 00 00 00  00 00 00 00 02 01 4c 55  |..............LU|
00000010  20 75 73 72 20 30 30 34  30 33 34 00 03 68 65 61  |  usr 004034..hea|
00000020  64 65 72 20 30 20 20 20  20 20 20 20 20 20 20 20  |der 0       |
00000030  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000050  75 73 72 20 30 30 34  30  33 34 20 20 20 20 20 20  |usr 004034     |
00000060  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000080  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000090  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000000a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000000c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000000d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000000e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000100  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000110  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000120  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000140  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000150  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000160  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000180  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000190  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000001a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000001c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000001d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000001e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000200  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000210  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000220  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000240  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000250  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000260  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000280  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000290  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000002a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000002c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000002d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000002e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000300  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000310  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000320  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000340  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000350  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000360  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000380  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000390  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000003a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000003c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000003d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000003e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000400  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000410  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000420  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000440  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000450  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000460  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000480  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000490  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000004a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000004c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000004d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000004e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000500  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000510  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000520  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000540  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000550  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000560  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000580  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000590  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000005a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000005c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000005d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000005e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000600  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000610  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000620  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000640  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000650  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000660  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000680  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000690  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000006a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000006c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000006d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000006e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000700  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000710  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000720  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000740  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000750  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000760  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000780  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000790  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000007a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000007c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000007d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000007e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000800  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000810  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000820  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000840  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000850  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000860  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000880  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000890  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000008a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000008c0  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
000008d0  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000008e0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000900  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000910  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000920  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000940  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000950  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
00000960  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
00000980  75 73 72 20 30 30 34  30  33 34 00 03 68 65 61 64  |usr 004034..head|
00000990  20 30 20 20 20 20 20 20  20 20 20 20 20 20 20 20  | 0       |
000009a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |               |
*
000009c0  75 73 72 20 30 30 34  30  33 3

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