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+# Brck -- a simple bit rot checker
+
+Brck is a simple bit rot checker for legacy file systems. It records and
+compares the modification times and cryptographic hash sums of regular files.
+When a file's hash changed but it's modification time did not, then Brck
+reports the file as corrupted so you have a chance to restore the file from
+backup. You do have backups, right? 😉
+
+Brck's original source code is hosted [here][brck-repo].
+
+## Installation
+
+Brck is available on [crates.io][brck-cratesio]. You can install it using
+Rust's package manager [Cargo][cargo].
+
+    $ cargo install brck
+
+## Usage
+
+Without any options, Brck will record all regular files in current working
+directory recursively and write those records to a gzipped `.brck` file.
+
+    $ brck
+
+When you run the same command again, Brck will compare the recorded files
+against the current file system and report any corrupted files.
+
+    $ brck
+    corrupted: ./test_file
+    Error: Found 1 denied difference
+
+Brck is quiet by default. Increase the verbosity using `-v` or request a
+summary using `-s`. Alternatively, enable the JSON output using `-J` and
+perform your own post-processing, e.g., using [jq][]:
+
+    $ brck -vvJ | jq -sr 'group_by(.type)[] | [.[0].type, length] | @tsv' 2>/dev/null
+    added   4
+    corrupted       1
+    unchanged       1219
+
+See the built-in help for all supported options:
+
+    $ brck --help
+
+## Features
+
+- Parallel sequential processing: Brck processes files in parallel, yet outputs
+  and records files in-order
+
+- One-pass: Brck reads your files only once
+
+- Constant memory: Brck's memory footprint is independent of the number of
+  processed files
+
+- Relative paths: Brck records relative paths such that you can move the
+  containing directory around
+
+- Quiet by default: Without any options, Brck prints denied differences to
+  standard output, and errors to standard error; nothing else
+
+- Human readable or machine readable, newline-delimited JSON output, at your
+  option
+
+- Graceful shutdown on the first interrupt signal, forceful immediate shutdown
+  on the second
+
+- [Pledged][pledge] and [unveiled][unveil] on OpenBSD
+
+## Limitations
+
+- Brck doesn't follow symlinks.
+
+- Brck doesn't track hardlinks. Performance will be suboptimal in the presence
+  of large hardlinked files because Brck hashes each copy individually.
+
+- Brck doesn't track reflinks. Modern copy-on-write file systems are out of
+  scope because they should check file content integrity themselves, like
+  OpenZFS and Btrfs do.
+
+- Brck may leak file meta data because its `.brck` file may have different
+  permissions than the listed files.
+
+- Brck doesn't respect platform-specific temporary directories such as `TMPDIR`
+  on UNIX. Instead, it creates its temporary files in the current working
+  directory, next to the `.brck` file. This way, Brck can update the files
+  atomically on POSIX-conform systems.
+
+- Brck may fail to remove its temporary files, e.g., in the event of a
+  segfault.
+
+## See also
+
+- Definition of *bit rot* in the [Jargon File][jargon]
+  ([archive][jargon-archive])
+
+- A similar Python program named [Bitrot][python-bitrot]
+
+- A similar Rust program named [Legdur][legdur] ([crates.io][legdur-cratesio])
+
+- A blog post on [Things UNIX can do atomically][rcrowley]
+
+[brck-repo]: https://git.skreutz.com/brck.git/
+[brck-cratesio]: https://crates.io/crates/brck
+[cargo]: https://doc.rust-lang.org/cargo/
+[jq]: https://jqlang.github.io/jq/
+[pledge]: https://man.openbsd.org/pledge
+[unveil]: https://man.openbsd.org/unveil
+[jargon]: http://www.catb.org/jargon/html/B/bit-rot.html
+[jargon-archive]: https://web.archive.org/web/20240312124910/http://www.catb.org/jargon/html/B/bit-rot.html
+[legdur]: https://git.cyplo.dev/cyplo/legdur
+[legdur-cratesio]: https://crates.io/crates/legdur
+[python-bitrot]: https://github.com/ambv/bitrot/
+[rcrowley]: https://web.archive.org/web/20160304224616/http://rcrowley.org/2010/01/06/things-unix-can-do-atomically