MD5(1)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

💅 MD5(1) — General Commands Manual 🎀

okay bestie, sit down, we're learning about checksums and honestly? it's giving main character energy. this is MD5(1), from the General Commands Manual, and it's a whole family of utilities, not just one. buckle up 🦋

🌸 NAME

md5, sha1, sha224, sha256, sha384, sha512, sha512t224, sha512t256, rmd160, skein256, skein512, skein1024, md5sum, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, sha512t224sum, sha512t256sum, rmd160sum, skein256sum, skein512sum, skein1024sum, shasum — calculate a message-digest fingerprint (checksum) for a file ✨

like, that's the whole squad. iconic honestly.

✨ SYNOPSIS ✨

md5 [-pqrtx] [-c string] [-s string] [file ...]
md5sum [-bctwz] [--binary] [--check] [--help] [--ignore-missing]
    [--quiet] [--status] [--strict] [--tag] [--text] [--version]
    [--warn] [--zero] [file ...]

    (All other hashes have the same options and usage.)
shasum [-0bchqstUvw] [--01] [-a | --algorithm alg] [--binary] [--check]
    [--help] [--ignore-missing] [--quiet] [--status] [--strict] [--tag]
    [--text] [--UNIVERSAL] [--version] [--warn] [file ...]
psst — that "(All other hashes have the same options and usage.)" line is literally part of the synopsis, don't skip it 💜

🦋 DESCRIPTION

okay so the md5, sha1, sha224, sha256, sha384, sha512, sha512t224, sha512t256, rmd160, skein256, skein512, and skein1024 utilities take as input a message of arbitrary length and produce as output a "fingerprint" or "message digest" of the input. ✨ lowkey magic, highkey math.

the md5sum, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, sha512t224sum, sha512t256sum, rmd160sum, skein256sum, skein512sum, and skein1024sum utilities do the same thing, but with command-line options and an output format that match those of their similary named GNU utilities. yes, "similary" — that's the original spelling, i'm not fixing it, it's canon now 🫶

the shasum utility does the same, but with command-line options and an output format that match those of the similarly named utility that ships with Perl. (note: this one got spelled right. character development.)

in all cases, each file listed on the command line is processed separately. and if no files are listed on the command line, or a file name is given as -, input is taken from stdin instead. classic stdin behavior, we love her 💖

the utility's different modes have different output formats, but in all cases, filenames containing unprintable characters are encoded as described in vis(3) using the VIS_CSTYLE | VIS_OCTAL style. yeah that's a real thing, write it down 📝

it is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given prespecified target message digest. like, conjectured — that's the word they used, i'm not softening it 🧚

the SHA-224, SHA-256, SHA-384, SHA-512, RIPEMD-160, and SKEIN algorithms are intended for digital signature applications, where a large file must be "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA. 👑

🚨 BIG RED FLAG TIME 🚨 the MD5 and SHA-1 algorithms have been proven to be vulnerable to practical collision attacks and should not be relied upon to produce unique outputs, nor should they be used as part of a cryptographic signature scheme. i'm being so serious rn. do not use these for security. periodt. 💀

SHA-512t256 is a version of SHA-512 truncated to only 256 bits. on 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but with the same level of security. the hashes are not interchangeable — fr fr, do not mix them up 🙈

SHA-512t224 is identical to SHA-512t256, but with the digest truncated to 224 bits. tiny queen 🎀

it is recommended that all new applications use SHA-512 or SKEIN-512 instead of one of the other hash functions. so like… do that? ✨

🎀 BSD OPTIONS 🎀

the following options are available in BSD mode, i.e. when the program is invoked with a name that does not end in "sum":

  • -c string, --check=string — compare the digest of the file against this string. if combined with the -q or --quiet option, the calculated digest is printed in addition to the exit status being set. (note that this option is not yet useful if multiple files are specified.) 🫶
  • -p, --passthrough — echo stdin to stdout and append the checksum to stdout. in this mode, any files specified on the command line are silently ignored. like, ghosted. 💅
  • -q, --quiet — quiet mode — only the checksum is printed out. overrides the -r or --reverse option. 🤫
  • -r, --reverse — reverses the format of the output. this helps with visual diffs. does nothing when combined with the -ptx options. 🦋
  • -s string, --string=string — print a checksum of the given string. in this mode, any files specified on the command line are silently ignored. (yes, silently again. it's a whole theme.) 🌸
  • -t, --time-trial — run a built-in time trial. for the -sum versions, this is a nop for compatibility with coreutils. ⏱️
  • -x, --self-test — run a built-in test script. 🧪

💖 GNU OPTIONS 💖

the following options are available in GNU mode, i.e. when the program is invoked with a name that ends in "sum":

  • -b, --binary — read files in binary mode. 🤖
  • -c, --check — the file passed as arguments must contain digest lines generated by the same digest algorithm in either classical BSD format or in GNU coreutils format. a line with the file name followed by a colon : and either OK or FAILED is written for each well-formed line in the digest file. if applicable, the number of failed comparisons and the number of lines that were skipped since they were not well-formed are printed at the end. the --quiet option can be used to quiesce the output unless there are mismatched entries in the digest. ✅
  • --help — print a usage message and exit. 🆘
  • --ignore-missing — when verifying checksums, ignore files for which checksums are given but which aren't found on disk. like, if they're not there, we simply don't perceive them 💅
  • --quiet — when verifying checksums, do not print anything unless the verification fails. 🤐
  • --status — when verifying checksums, do not print anything at all. the exit code will reflect whether verification succeeded. silent but deadly 🫥
  • --strict — when verifying checksums, fail if the input is malformed. no sloppy input tolerated 🚫
  • --tag — produce BSD-style output. 🏷️
  • -t, --text — read files in text mode. this is the default. note that this implementation does not differentiate between binary and text mode. (so -b and -t are basically vibes here, but they're documented vibes) 📄
  • --version — print version information and exit. 🏆
  • -w, --warn — when verifying checksums, warn about malformed input. ⚠️
  • -z, --zero — terminate output lines with NUL rather than with newline. fancy ✨

🌈 PERL OPTIONS 🌈

the following options are available in Perl mode, i.e. when the program is invoked with the name shasum:

  • -0, --01 — read files in bits mode: ASCII 0 and 1 characters correspond to 0 and 1 bits, respectively, and all other characters are ignored. see "BUGS". 😬 (yes, they're pointing you at BUGS. ominous.)
  • -a alg, --algorithm alg — use the specified algorithm: 1 for SHA-1 (default), xxx for xxx-bit SHA-2 (e.g. 256 for SHA-256) or xxxyyy for xxx-bit SHA-2 truncated to yyy bits (e.g. 512224 for SHA-512/224). 🧠
  • -b, --binary — read files in binary mode. 🤖
  • -c, --check — the file passed as arguments must contain digest lines generated by the same digest algorithm in either classical BSD format or in GNU coreutils format. a line with the file name followed by a colon : and either OK or FAILED is written for each well-formed line in the digest file. if applicable, the number of failed comparisons and the number of lines that were skipped since they were not well-formed are printed at the end. the --quiet option can be used to quiesce the output unless there are mismatched entries in the digest. ✅
  • --help — print a usage message and exit. 🆘
  • --ignore-missing — when verifying checksums, ignore files for which checksums are given but which aren't found on disk. 👻
  • --quiet — when verifying checksums, do not print anything unless the verification fails. 🤐
  • --status — when verifying checksums, do not print anything at all. the exit code will reflect whether verification succeeded. 🫥
  • --strict — when verifying checksums, fail if the input is malformed. 🚫
  • --tag — produce BSD-style output. 🏷️
  • -t, --text — read files in text mode. this is the default. note that this implementation does not differentiate between binary and text mode. 📄
  • -U, --UNIVERSAL — read files in universal mode: any CR-LF pair, as well as any CR not followed by LF, is translated to LF before the digest is computed. 🌍 (yes, all caps, that's how they wrote it, respect it)
  • --version — print version information and exit. 🏆
  • -w, --warn — when verifying checksums, warn about malformed input. ⚠️

⭐ EXIT STATUS ⭐

okay so this part is important, bestie, the exit codes are the whole personality 👑

the md5, sha1, sha224, sha256, sha384, sha512, sha512t224, sha512t256, rmd160, skein256, skein512, and skein1024 utilities exit 0 on success, 1 if at least one of the input files could not be read, and 2 if at least one file does not have the same hash as the -c option. 🎯

the md5sum, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, sha512t224sum, sha512t256sum, rmd160, skein256, skein512, skein1024 and shasum utilities exit 0 on success and 1 if at least one of the input files could not be read or, when verifying checksums, does not have the expected checksum. 🫶

🙈 and yes — before you come for me — that second list really does say rmd160, skein256, skein512, skein1024 with no sum on the end, unlike the first list. that's how it's written. i am simply the messenger. 💜

okay that's the first chunk!! there's more coming, don't you dare close the terminal 🦋✨

✨ EXAMPLES ✨

Okay bestie, this is where it gets fun — real commands, real outputs, all exact. Let’s go 💅

Calculate the MD5 checksum of the string “Hello”.

$ md5 -s Hello
MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7

Same as above, but note the absence of the newline character in the input string:

$ echo -n Hello | md5
8b1a9953c4611296a827abf8c47804d7

Calculate the checksum of multiple files reversing the output:

$ md5 -r /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf

This is almost but not quite identical to the output from GNU mode:

$ md5sum /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6  /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd  /etc/rc.conf

Note the two spaces between hash and file name. If binary mode is requested, they are instead separated by a space and an asterisk:

$ md5sum -b /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 */boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd */etc/rc.conf

Write the digest for /boot/loader.conf in a file named digest. Then calculate the checksum again and validate it against the checksum string extracted from the digest file:

$ md5 /boot/loader.conf > digest && md5 -c $(cut -f2 -d= digest) /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6

Same as above but comparing the digest against an invalid string (“randomstring”), which results in a failure.

$ md5 -c randomstring /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6 [ Failed ]

In GNU mode, the -c option does not compare against a hash string passed as parameter. Instead, it expects a digest file, as created under the name digest for /boot/loader.conf in the example above.

$ md5sum -c digest
/boot/loader.conf: OK

The digest file may contain any number of lines in the format generated in either BSD or GNU mode. If a hash value does not match the file, “FAILED” is printed instead of “OK”.

🦋 SEE ALSO 🦋

🚨 CAVEATS 🚨

Bestie, listen up — this part matters 👀

The encoding used for file names containing non-printable characters is incompatible with that used by GNU coreutils. The encoding used by GNU coreutils is non-reversible, in that certain non-printable characters are encoded while others are simply omitted. The encoding used by this utility, on the other hand, is fully reversible.

If interoperability with GNU coreutils is required, it is recommended to ensure that all file names contain only printable characters.

💀 BUGS 💀

In bits mode, the original shasum script is capable of processing inputs of arbitrary length. This implementation is not, and will issue an error if the input length is not a multiple of eight bits.

Not me being iconic but also having this one very specific limitation 😭 Keep it in mind, bestie.

👑 ACKNOWLEDGMENTS 👑

This utility was originally derived from a program which was placed in the public domain for free general use by RSA Data Security.

Support for SHA-1 and RIPEMD-160 was added by Oliver Eikemeier <eik@FreeBSD.org>.

Support for SHA-2 was added by Colin Percival <cperciva@FreeBSD.org> and Allan Jude <allanjude@FreeBSD.org>.

Support for SKEIN was added by Allan Jude <allanjude@FreeBSD.org>.

Compatibility with GNU coreutils was added by Warner Losh <imp@FreeBSD.org> and much expanded by Dag-Erling Smørgrav <des@FreeBSD.org>, who also added Perl compatibility.

Later, bestie 💖 This page is MD5(1), source/version Debian, dated April 6, 2026 — now go checksum something cute and slay the day ✨💅

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