cksum

Display file checksums and block counts.

SYNTAX
       cksum [-o 1 | 2 | 3] [file ...]
       sum [file ...]

The sum utility is identical to cksum, except that it defaults to using historic algorithm 1, as described below. It is provided for compatibility only.

Options
     -o	     Use historic algorithms instead of the (superior) default one.

	     Algorithm 1 is the algorithm used by historic BSD systems as the
	     sum(1) algorithm and by historic AT&T System V UNIX systems as
	     the sum(1) algorithm when using the -r option.  This is a 16-bit
	     checksum, with a right rotation before each addition; overflow is
	     discarded.

	     Algorithm 2 is the algorithm used by historic AT&T System V UNIX
	     systems as the default sum(1) algorithm.  This is a 32-bit check-
	     sum, and is defined as follows:

		   s = sum of all bytes;
		   r = s % 2^16 + (s % 2^32) / 2^16;
		   cksum = (r % 2^16) + r / 2^16;

	     Algorithm 3 is what is commonly called the `32bit CRC' algorithm.
	     This is a 32-bit checksum.

	     Both algorithm 1 and 2 write to the standard output the same
	     fields as the default algorithm except that the size of the file
	     in bytes is replaced with the size of the file in blocks.	For
	     historic reasons, the block size is 1024 for algorithm 1 and 512
	     for algorithm 2.  Partial blocks are rounded up.

Notes
cksum writes to the standard output three (whitespace separated) fields for each input file:

  CRC_checksum  Total_no_of_octets  Filename

If no file name is specified, the standard input is used and no file name is written.

The cksum and sum utilities exit 0 on success, and >0 if an error occurs.
The default CRC used is based on the polynomial used for CRC error check- ing in the networking standard ISO/IEC 8802-3:1989.

The claim of 'scientific consensus' is the first refuge of scoundrels - Michael Crichton

Related commands:

md5(1)

Equivalent BASH command:

cksum - Display file checksums and block counts