SHA256(1) OpenBSD Reference Manual SHA256(1)
sha256 - calculate a message-digest fingerprint (checksum) for a file
sha256 [-bpqrtx] [-c [checklist ...]] [-s string] [file ...]
sha256 takes as input a message of arbitrary length and produces as
output a 256-bit "fingerprint" or "message digest" of the input. 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.
The SHA-256 algorithm is 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.
The options are as follows:
-b Output checksums in base64 notation, not hexadecimal.
-c [checklist ...]
Compares all checksums contained in the file checklist with newly
computed checksums for the corresponding files. Output consists
of the digest used, the file name, and an OK or FAILED for the
result of the comparison. This will validate any of the
supported checksums (see cksum(1)). If no file is given, stdin
-p Echoes stdin to stdout and appends the SHA-256 sum to stdout.
-q Only print the checksum (quiet mode).
-r Reverse the format of the hash algorithm output, making it match
the output format used by cksum(1).
Prints a checksum of the given string.
-t Runs a built-in time trial. Specifying -t multiple times results
in the number of rounds being multiplied by 10 for each
-x Runs a built-in test script.
The SHA-256 sum of each file listed on the command line is printed after
the options are processed.
The sha256 command is shorthand for
cksum -a sha256
The sha256 utility exits 0 on success, and >0 if an error occurs.
cksum(1), md5(1), sha1(1)
Secure Hash Standard, FIPS PUB 180-2.
OpenBSD 5.4 July 8, 2012 OpenBSD 5.4
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