I'm the author of Biff. I just wanted to share a really cool example of something that Biff can do that I _think_ is kinda hard to do otherwise. (And also, I want to make an assertion about it and I hope this will lead to me being wrong and learning something new.)
The use case is: "I want to see a list of all files in a repository, sorted in ascending order of when it was most recently changed according to source control. I also want to highlight the time with color, make it be in local time and format it in my own bespoke way using strftime." Here's the full command (run from the root of https://github.com/BurntSushi/ripgrep):
$ git ls-files |
biff tag exec git log -n1 --format='%aI' |
biff time in system |
biff time cmp ge 2026-01-01 |
biff time cmp lt 2026-04-01 |
biff time sort |
biff time fmt -f '%a %Y-%m-%d %H:%M:%S' |
biff untag -f '{tag}|t{data}'
Thu 2026-02-12 20:39:46 crates/ignore/src/default_types.rs
Fri 2026-02-20 16:06:29 crates/core/flags/config.rs
Fri 2026-02-27 11:25:19 GUIDE.md
Fri 2026-02-27 11:25:19 crates/core/flags/defs.rs
If you run this on a big repository, it will take quite a lot of time because `git log -n1` takes a long time. I think this is the fastest way to get the most recent commit time on a single file? (That's the assertion that I hope someone can correct me on!) In any case, `biff tag exec` is using parallelism under the hood to make this even faster.
Quick Note: You can put the pipe operator where your backslash is and you won’t have to escape the newline character. Works in bash, zsh and ksh (what I’ve tested).
NAME
biff -- be notified if mail arrives and who it is from
[…]
HISTORY
The biff command appeared in 4.0BSD. It was named after the dog of
Heidi Stettner. He died in August 1993, at 15.
Eric Cooper, a student contemporary to Foderero and
Stettner, reports that the dog would bark at the mail
carrier,[4][5] making it a natural choice for the name
of a mail notification system. Stettner herself
contradicts this.[3][6]
If I type in "biff" on a Debian CLI, what should I expect the behaviour of the program that is executed to be? Will it be something about mail or time?
That's... not terrible. Biff isn't exactly popular (yet?), so a name change isn't out of the question. Both of those names (and `biff`) are already taken on crates.io. Which is maybe not a huge problem. IDK. Naming is hard.
Sending mail to root@<whatever> really did use to be a pretty reliable way of getting somebody useful's attention - the early-to-mid 90s equivalent of making a "Can someone from Google please unlock my account?" post on HN.
Under Debian/Ubuntu, when Postfix is installed, part of the standard list of questions that dpkg-reconfigure asks you is how you want mail flow to work: you can give it a central smarthost. So any local mail gets sent on, and on the central mail hub you can tell it to send root@ to someplace useful:
This is a fair critique actually. And this shouldn't be the default. It is for now because I haven't gotten around to making Biff read your POSIX locale settings and converting them to a Unicode locale. If you build with `cargo build --release --features locale` (or get Biff from a release binary), then you can do:
$ BIFF_LOCALE=en-US biff
Thu, May 28, 2026, 6:38:09 AM EDT
If that doesn't work, then you can enable logging to see an error message:
$ BIFF_LOCALE=watwat BIFF_LOG=warn biff
2026-05-28T06:39:08.876336708-04:00[America/New_York]|WARN|src/main.rs:76: reading `BIFF_LOCALE` failed, using unknown locale `und`: failed to parse `BIFF_LOCALE` environment variable: The given language subtag is invalid
2026 M05 28, Thu 06:39:08
What you're seeing is what ICU4X does when the user's locale is unknown or undetermined. The `M` prefix occurs to indicate that the number is the month, and is unrelated to the name. For example:
$ BIFF_LOCALE=watwat biff time fmt -f '%c' '1 month'
2026 M06 28, Sun 06:39:50
I'm the author of Biff. I just wanted to share a really cool example of something that Biff can do that I _think_ is kinda hard to do otherwise. (And also, I want to make an assertion about it and I hope this will lead to me being wrong and learning something new.)
The use case is: "I want to see a list of all files in a repository, sorted in ascending order of when it was most recently changed according to source control. I also want to highlight the time with color, make it be in local time and format it in my own bespoke way using strftime." Here's the full command (run from the root of https://github.com/BurntSushi/ripgrep):
Or even ask for a specific time window: If you run this on a big repository, it will take quite a lot of time because `git log -n1` takes a long time. I think this is the fastest way to get the most recent commit time on a single file? (That's the assertion that I hope someone can correct me on!) In any case, `biff tag exec` is using parallelism under the hood to make this even faster.Thank you for making cool stuff and sharing it with us.
Quick Note: You can put the pipe operator where your backslash is and you won’t have to escape the newline character. Works in bash, zsh and ksh (what I’ve tested).
Oh nice thank you!
No, Biff informs the system whether you want to be notified when mail arrives during the current terminal session.
I.e.,
* https://man.freebsd.org/cgi/man.cgi?query=biff * https://en.wikipedia.org/wiki/Biff_(Unix)Also: <https://manpages.debian.org/stable/biff/biff.1.en.html>
Yeah the name collision is unfortunate, but probably fine. The name Biff was just too good to pass up.
The name comes from the fact that Biff is a character in Back to the Future, and it rhymes with Jiff[1]. Jiff is the datetime library that Biff uses.
"Make like a tree and get out of here!" https://www.youtube.com/shorts/9Jabplo2pZU
[1]: https://github.com/BurntSushi/jiff
> Yeah the name collision is unfortunate, but probably fine. The name Biff was just too good to pass up.
So if I do an "apt install biff" on Debian (or Ubuntu) what will happen?
* https://packages.debian.org/search?keywords=biff
If I type in "biff" on a Debian CLI, what should I expect the behaviour of the program that is executed to be? Will it be something about mail or time?
I honestly don't know. Which is... Not Great.
It was a great opportunity to name a unix tool "mcfly" or just "Marty" for time manipulation. Better luck next time, I guess.
That's... not terrible. Biff isn't exactly popular (yet?), so a name change isn't out of the question. Both of those names (and `biff`) are already taken on crates.io. Which is maybe not a huge problem. IDK. Naming is hard.
https://crates.io/search?q=bttf
// backronym bttf stands for biff time to format
I like this
Griff is still available for future projects or Buford if you create a throwback project.
All short names, that is, pronounceable strings of 4 or maybe even 5 letters are already taken. Some of them taken many times over.
I think fewer people now care about mail notifications in a terminal session than about wrangling datetimes on the command line.
exactly. and chromium is a good looking space shooter with too few levels!
Yes I'm sure root is anxious to read all the mail in their local mailbox
Sending mail to root@<whatever> really did use to be a pretty reliable way of getting somebody useful's attention - the early-to-mid 90s equivalent of making a "Can someone from Google please unlock my account?" post on HN.
Under Debian/Ubuntu, when Postfix is installed, part of the standard list of questions that dpkg-reconfigure asks you is how you want mail flow to work: you can give it a central smarthost. So any local mail gets sent on, and on the central mail hub you can tell it to send root@ to someplace useful:
* https://wiki.debian.org/Postfix#Forward_Emails
I am a happy user of dateutils [0], but I will try out Biff and see which one is more ergonomic.
[0]: https://www.fresse.org/dateutils/
Yes! dateutils is great! I have a comparison about it here: https://github.com/BurntSushi/biff/blob/master/COMPARISON.md...
The comparison with GNU date is also likely informative.
Same dude that made jiff. Love that library, so I'm assuming biff is built on top of jiff.
also made ripgrep
I remember when biff was what we ran in a CSH to be informed of new email. I don’t remember if this was a local UCB tool or if it was part of BSD.
% biff
2026 M05 28, Thu 17:27:46
Ahh, the month of M05
This is a fair critique actually. And this shouldn't be the default. It is for now because I haven't gotten around to making Biff read your POSIX locale settings and converting them to a Unicode locale. If you build with `cargo build --release --features locale` (or get Biff from a release binary), then you can do:
If that doesn't work, then you can enable logging to see an error message: What you're seeing is what ICU4X does when the user's locale is unknown or undetermined. The `M` prefix occurs to indicate that the number is the month, and is unrelated to the name. For example:just between a04 and j06 yes
Looking forward to the J07 04 holiday