# Extensions over GNU
Though the main goal of the project is compatibility, uutils supports a few
features that are not supported by GNU coreutils. We take care not to introduce
features that are incompatible with the GNU coreutils. Below is a list of uutils
extensions.
## General
GNU coreutils provides two ways to define short options taking an argument:
```
$ ls -w 80
$ ls -w80
```
We support a third way:
```
$ ls -w=80
```
## `env`
GNU `env` allows the empty string to be used as an environment variable name.
This is unsupported by uutils, and it will show a warning on any such
assignment.
`env` has an additional `-f`/`--file` flag that can
parse `.env` files and set variables accordingly. This feature is adopted from `dotenv` style
packages.
## `cp`
`cp` can display a progress bar when the `-g`/`--progress` flag is set.
## `mv`
`mv` can display a progress bar when the `-g`/`--progress` flag is set.
## `hashsum`
This utility does not exist in GNU coreutils. `hashsum` is a utility that
supports computing the checksums with several algorithms. The flags and options
are identical to the `*sum` family of utils (`sha1sum`, `sha256sum`, `b2sum`,
etc.).
## `b3sum`
This utility does not exist in GNU coreutils. The behavior is modeled after both
the `b2sum` utility of GNU and the
[`b3sum`](https://github.com/BLAKE3-team/BLAKE3) utility by the BLAKE3 team and
supports the `--no-names` option that does not appear in the GNU util.
## `more`
We provide a simple implementation of `more`, which is not part of GNU
coreutils. We do not aim for full compatibility with the `more` utility from
`util-linux`. Features from more modern pagers (like `less` and `bat`) are
therefore welcomed.
## `cut`
`cut` can separate fields by whitespace (Space and Tab) with `-w` flag. This
feature is adopted from [FreeBSD](https://www.freebsd.org/cgi/man.cgi?cut).
## `fmt`
`fmt` has additional flags for prefixes: `-P`/`--skip-prefix`, `-x`/`--exact-prefix`, and
`-X`/`--exact-skip-prefix`. With `-m`/`--preserve-headers`, an attempt is made to detect and preserve
mail headers in the input. `-q`/`--quick` breaks lines more quickly. And `-T`/`--tab-width` defines the
number of spaces representing a tab when determining the line length.
## `seq`
`seq` provides `-t`/`--terminator` to set the terminator character.
## `ls`
GNU `ls` provides two ways to use a long listing format: `-l` and `--format=long`. We support a
third way: `--long`.
GNU `ls --sort=VALUE` only supports special non-default sort orders.
We support `--sort=name`, which makes it possible to override an earlier value.
## `du`
`du` allows `birth` and `creation` as values for the `--time` argument to show the creation time. It
also provides a `-v`/`--verbose` flag.
## `id`
`id` has three additional flags:
* `-P` displays the id as a password file entry
* `-p` makes the output human-readable
* `-A` displays the process audit user ID
## `uptime`
Similar to the proc-ps implementation and unlike GNU/Coreutils, `uptime` provides `-s`/`--since` to show since when the system is up.
## `base32/base64/basenc`
Just like on macOS, `base32/base64/basenc` provides `-D` to decode data.
## `shred`
The number of random passes is deterministic in both GNU and uutils. However, uutils `shred` computes the number of random passes in a simplified way, specifically `max(3, x / 10)`, which is very close but not identical to the number of random passes that GNU would do. This also satisfies an expectation that reasonable users might have, namely that the number of random passes increases monotonically with the number of passes overall; GNU `shred` violates this assumption.
