shattr

A shatag clone in Ceylon.

Status

Basic features implemented:

• --lookup: Lookup for duplicates.
• --scrub: Recompute checksums to detect silent corruption.
• --tag: Compute new checksums for files that don't have one, or when it is outdated.

Why

shatag -rl is slow since it needs to query SQL database for every file. shattr reads all SHA-256 checksums in memory instead.

Installation

With ceylon

If you have Ceylon installed, you can download the .car archive (< 4K) at Releases and put it into Ceylon module repository. If your ceylon is recent enough, you can package it to a jar file via ceylon --fat-jar. Running with java -jar starts faster than ceylon run.

With java directly

If you have Java Runtime (7+) installed , but not Ceylon, you can download the fat jar file (3.2M).

Compile manually

Clone this repository and run ceylon compile.

Tested with Ceylon 1.2+. May work with older versions.

Usage

Lookup

$SHATTR_COMMAND -l PATH_TO_HASHLIST

will print status of files under the current directory.

N empty file
D duplicated file
U unique file
? unknown file (without `sha256` xattr, no read permission, etc)

$SHATTR_COMMAND is one of:

• ceylon run io.github.weakish.shattr if using Ceylon;
• java -jar /path/to/io.github.weakish.shattr-0.2.0.jar if using java directly.

If PATH_TO_HASHLIST is not specified, shattr will use ~/.shatagdb-hash-list.txt.

Hash list format

PATH_TO_HASHLIST is a text file, containing all SHA256 hashes of known files, one per line.

For example, if using shatag with an sqlite3 backend, PATH_TO_HASHLIST can be produced via:

sqlite3 -noheader -csv ~/.shatagdb "select hash from contents;" > hashlist.csv

Customize output

By default we use a git status style output. You can change output format style with --format FORMAT. FORMAT is one of git, inotifywait, and csv. --format FORMAT should be specified before hash list file.

--format inotifywait

EMPTY empty file
DUMPLICATED duplicated file
UNIQUE unique file
UNKNOWN file (without `sha256` xattr, no read permission, etc)

--format csv

Like --format inotifywait, but separated with comma ,, with path name quoted.

EMPTY,"empty_file.txt"
UNIQUE,"A file containing spaces and ""double quotes"""

--format your_own

You need to write a formatting function typed String(Status, Path). Then register it in command line option parsing code in run().

scrub/tag

$SHATTR_COMMAND -s
$SHATTR_COMMAND -t

Will compute checksums for all files under current directory (recursively).

Unlike shatag, -t will warn if checksum changes.

Contribute

Send pull requests at https://github.com/weakish/shattr.

Coding style

Prefer if . then . else . to . then . else .

We feel A then B else C is confusing.

Readers may think A then B else C is A ? B : C in other languages, but they are not the same:

1. A then B else C is actually (A then B) else C:

   • A then B evaluates to B if A is not null, otherwise evaluates to null.
   • X else Y evaluates to X if X is not null, otherwise evaluates to Y.

2. Thus the type of B is T given T satisfies Object, i.e. requires to not be null.

I think if (A) then B else C is much cleaner.

Only use i++ to increase i.

y=i++ and y=++i is really confusing to me.

So I prefer to only uses i++ to increase i, e.g. in a while loop. I think a meaningful evaluated value of i++ should be void if the a programming language allows ++.

Same applies to i-- and --i.

Prefer functions to classes

We prefer to declare classes for new types (or type aliases).

Other

If you disagree the above, file an issue.

Send pull requests to add new coding style.

Please do not add formatting style such as use two spaces and closing braces on their own line. Formatting style is unlikely to affect readability of code, and can be auto adjusted via ceylon format.

License

0BSD.