shamv

The shamv ("SHA move") utility renames files, making their names "almost" unique. It uses a cryptographic hash function, SHA-256 by default, to generate a 256-bit (32-byte) digest based on the content of the file that is used to derive the filename.

Because the cryptographic hash function used to generate the name is deterministic, if two files have exactly the same content (bit-by-bit), then their names will also be the same. This way, if you find two files with the same name, you can determine (with a high-degree of certainty) that they are copies of the same file.

The shamv utility is prototype software for exploring different use case of files named after their cryptographic hash values using a general purpose command line interface. It is not intended to be used in production environments.

One use case for shamv is managing screenshots and other attachments imported into note-taking software such as Obsidian. Screenshot software provided by some operating systems may use naming conventions for screenshots that derive the filename, e.g., from the date the screenshot is taken (Screenshot 2021-04-22.png). This can lead to conflicts with files which have the same name. While there are plugins and scripts available for this purpose, shamv aims to be a general purpose tool for manipulating files named after their hash values and uses modern, cryptographic primitives based on the SHA-2 NIST standard.

Another use case for shamv is file archival where files indexed by their cryptographic hash can be immediately located from a filesystem based on their hash value. A property of shamv-named files is that the integrity of the file contents can be verified using the name of the file. Similarly digitally signing a manifest of filenames is sufficient to verify not only the list of files, but their content.

Further suggestions for use cases and feature requests can be submitted as Github Issues.

Usage

shamv [OPTION...] FILE[...]

The shamv utility renames the file named by the FILE operand to a
destination path that is formed from the SHA-2 hash of the content
of the file.

If the FILE operand includes a filename extension that consists of one or
more suffixes, each separated by a dot (.) character, the destination path
is formed by the concatenation of the SHA-2 hash and the filename extension
suffixes of the original FILE name.

Mandatory arguments to long options are mandatory for short options too.
 -a, --algorithm      The SHA-2 algorithm to use: sha224, sha256 (default),
                      sha384, or sha512.
 -n, --dry-run        Display the current and new filenames but do not
                      perform the rename.
 -h, --help           Print this help and exit.
 -V, --version        Print the version of the program and exit.

License

The code of shamv is made available under a dual-license. This means that you can decide which license you wish to use when using the software. The two options are:

• a) You can use the Apache License, Version 2.0 or any later version published by the Apache Software Foundation

• b) You can use the MIT license published by the Massachusetts Institute of Technology.