tarcat

tarcat -f archive.tar archive1.tar archive2.tar ...

-f archive.tar
    Specifies the name of the final, concatenated tar archive.
If not specified, output defaults to standard output (stdout). Use "-" for stdout.
This option is mandatory and specifies where the consolidated archive will be written.

archive1.tar archive2.tar ...
    Lists the tar archive files to be concatenated. These are the input archives that will be merged into the single output archive specified with `-f`.

-v
    Verbose mode. It prints the name of each input archive as it is being processed. Useful for monitoring progress.

The `tarcat` command efficiently concatenates multiple tar archives into a single, larger tar archive. It's designed to work specifically with tar archives and provides a fast method for merging them without re-compressing the data if the original archives were not compressed.

Unlike simply using `cat`, `tarcat` ensures that the resulting archive is a valid tar archive, by properly handling the end-of-archive markers, which are two consecutive 512-byte blocks of zeros. This is crucial for tar readers to correctly identify the end of the archive. Using `cat` on tar archives will not add the needed end-of-archive markers.

The utility is primarily beneficial when dealing with backups or collections of data spread across several archive files. Instead of extracting each archive individually and then re-archiving, `tarcat` offers a quicker, more direct approach.

tarcat doesn't handle compression. If the input archives are compressed (e.g., using gzip or bzip2), the resulting concatenated archive will not be compressed. You'll need to compress the output archive separately if compression is required.

It's also important to ensure that the archives being concatenated are compatible in terms of format and content. Incompatible archives may lead to unpredictable results. The command does not check format compatibility.

Here are some usage examples:

To create a combined archive named `backup.tar` from `part1.tar`, `part2.tar`, and `part3.tar`:
tarcat -f backup.tar part1.tar part2.tar part3.tar

To output the concatenated archive to standard output:
tarcat -f - part1.tar part2.tar | gzip > combined.tar.gz

To concatenate in verbose mode and display the archives being processed:
tarcat -v -f combined.tar part1.tar part2.tar

The tarcat command typically exits with a status code of 0 upon successful completion and a non-zero status code if errors are encountered, such as if a specified archive file cannot be found.

The origin of `tarcat` is somewhat obscure, often found in shell scripts and utilities for backup purposes. It's not a core utility in all Linux distributions, often being provided as a standalone script or as part of a larger set of archive management tools. Its development likely stemmed from the need to efficiently merge tar archives without the overhead of extracting and re-archiving.

tar(1), cat(1), gzip(1), bzip2(1)