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.TH B256SUM 1 blakesum
.SH NAME
b256sum - Compute and check BLAKE-256 message digests
.SH SYNOPSIS
.B b256sum
[-S salt] [-c | -B | -L | -U] [-xz]
.RI [ file "] ..."
.SH DESCRIPTION
Print or check BLAKE-256 checksums.
.SH OPTIONS
The
.B b256sum
utility conforms to the Base Definitions volume of POSIX.1-2017,
.IR "Section 12.2" ,
.IR "Utility Syntax Guidelines" .
.PP
The following options are supported:
.TP
.B -B
Output checksums in binary representation. This suppresses
the filenames and checksum delimiters. Only the checksums
are printed.
.TP
.B -c
Read BLAKE-256 sums from the file and check them against
the files on your systems. The input files files should be
formatted as the output of this program, or similarly.
This is not going to work if any of the filenames in the
input files starts with <space> or <tab>, or if they
contain a <newline>, unless the
.B -z
option is also used.
.TP
.B -L
Output checksums in lower-case hexadecimal representation. (Default)
.TP
.BI "-S " salt
Specify a 16-byte salt that the BLAKE-256 algorithm shall use.
This salt shall be expressed in full length hexadecimal: 32
hexadecimal digits, or rather 16 pairs of hexadecimal digits,
ordered from left to right to specify the values from index 0
to the last byte. In each pair, the left digit stores the high
bits of the byte, and the right digit stores the low bits of
the byte. For example, the digit pair
.B 80
represents a byte with the decimal value 128, whereas the
digit pair
.B 08
represents a byte with the decimal value 8. The pairs
are joined without any delimiters, and no byte may be
omitted. So, for a salt where each byte's value is its
index, the salt is expressed as
.BR 000102030405060708090a0b0c0d0e0f ,
however each letter may be either small or capital.
If no salt is specified, an all-zeroes salt is used.
.TP
.B -U
Output checksums in upper-case hexadecimal representation.
.TP
.B -x
Convert input files from hexadecimal form to binary form
before calculating the checksums.
.TP
.B -z
Lines end with NUL instead of LF. If used with
.BR -c ,
this applies to read files (not the output), but it will
also apply more strict parsing and allow any whitespace
in file names.
.SH OPERANDS
The following operands are supported:
.TP
.I file
File to read. The standard input will be used
.B -
or no
.I file
is specified.
.SH EXIT STATUS
.TP
0
Successful completion.
.TP
1
Checksums did not match or a file did not exist.
.TP
2
An error occurred.
.SH SEE ALSO
.BR bsum (1),
.BR b2sum (1),
.BR b224sum (1),
.BR b384sum (1),
.BR b512sum (1)
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