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to list what is in a tar ball `tar -vtf tarball.tar`

to extract a particular entity 'tar -vxf tarball.tar path_in tarball_to_entity`

edit: good points on it not being efficient for large archives, just demonstrating it is possible.

A tar is a linked list of file paths and contents, it cannot be indexed to a particular file. A compressed tar has to first be decompressed and then the chain of links traversed. Accessing a file in compressed tar is o(n) with where the file is placed within the compressed tar stream.

It isn't that it is possible, it is that is horribly inefficient.

Zips on other hand unify storage and compression such that one has random access to particular file, hence most modern file formats are zips with xml or json inside.

The problem is that to know what files are in the tarball you have to read the whole thing. If the archive is large that's a lot of reading just to get a file list.

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