B2SUM(1)

📦
version 9.10 · 5 versions
, in ubuntu stonking

💖 B2SUM(1) 💖

okay bestie, welcome to b2sum — she's a User Command in the GNU coreutils fam and she computes AND checks BLAKE2 message digests. her whole personality is "hashing things, but make it certified". let's get into it ✨

✨ NAME ✨

b2sum — compute and check BLAKE2 message digest 🦋

🌸 SYNOPSIS 🌸

b2sum [OPTION]... [FILE]...

👑 DESCRIPTION 👑

So what she actually DOES: prints or checks BLAKE2b (512-bit) checksums. she's the legacy interface to the cksum utility, which — iykyk — means she's been around and she's still that girl. 💅

If you give her no FILE, or if FILE is literally just -, she reads standard input. stdin girlies rise up 🙈

okay and a big one, truly no cap: mandatory arguments to long options are mandatory for short options too. like the rule is the rule, both ways, periodt.

  • -b, --binary — reads in binary mode 💀
  • -c, --check — reads checksums out of the FILEs and, like, checks them ✨
  • -l, --length=BITS — this is the digest length in bits. heads up bestie, it must not exceed the max size, and it must be a multiple of 8 for blake2b; and for sha2 or sha3 it must be 224, 256, 384, or 512. so no freestyling with the numbers okay 🎀
  • --tag — makes a BSD-style checksum, very chic
  • -t, --text — reads in text mode, which is the default btw 🌈
  • -z, --zero — every output line ends with a NUL instead of a newline, AND it disables file name escaping. that second part is lowkey important, don't skip it 🫶

🔥 the five options that are literally only useful when you're verifying checksums 🔥

bestie these are the verification-only girlies, they do NOTHING unless you're checking 👑

  • --ignore-missing — doesn't fail and doesn't report status for files that are missing. she's unbothered 💅
  • --quiet — doesn't print OK for every single file that verified successfully. for when the success spam is too much 😭
  • --status — outputs absolutely nothing. the status code is the whole entire story. silence is the vibe 🔇
  • --strict — exits non-zero for checksum lines that are improperly formatted. she's strict because she loves you 🎀
  • -w, --warn — warns you about improperly formatted checksum lines, like a good friend would 🦋
  • --help — displays this help and exits ⭐
  • --version — outputs version information and exits 👑

the sums get computed exactly as described in RFC 7693, no notes. 📜

when you're checking, the input should be a former output of this program — like, she's checking her own receipts, it's a self-care thing.

and the default mode prints a line with: the checksum, then a space, then a character that indicates the input mode (* for binary, ' ' for text or where binary is insignificant), then the name, for each FILE.

also, real talk: there is no difference between binary mode and text mode on GNU systems. so if you were stressed about picking — on GNU, you can just chill 🌈

🎀 AUTHOR 🎀

Written by Padraig Brady and Samuel Neves. icons only, we stan 👑

💜 REPORTING BUGS 💜

found a bug? not to be dramatic but tell someone:

🦋 SEE ALSO 🦋

Packaged by Ubuntu (9.10-1ubuntu2)

Copyright © 2026 Free Software Foundation, Inc.

License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.

and that's the whole page bestie 💖 this one's from GNU coreutils 9.10, dated August 2026 — go hash something and feel gorgeous doing it. slay, stay checksummed, periodt. 👑✨

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