cksum (n) - Linux Manuals

cksum: Calculate a cksum(1) compatible checksum


cksum - Calculate a

cksum(1) compatible checksum


package require Tcl 8.2

package require cksum ?1.1.3?

::crc::cksum ?-format format? ?-chunksize size? [ -channel chan | -filename file | string ]


::crc::CksumUpdate token data

::crc::CksumFinal token


This package provides a Tcl implementation of the cksum(1) algorithm based upon information provided at in the GNU implementation of this program as part of the GNU Textutils 2.0 package.


::crc::cksum ?-format format? ?-chunksize size? [ -channel chan | -filename file | string ]
The command takes string data or a channel or file name and returns a checksum value calculated using the cksum(1) algorithm. The result is formatted using the format(n) specifier provided or as an unsigned integer (%u) by default.


-channel name
Return a checksum for the data read from a channel. The command will read data from the channel until the eof is true. If you need to be able to process events during this calculation see the PROGRAMMING INTERFACE section
-filename name
This is a convenience option that opens the specified file, sets the encoding to binary and then acts as if the -channel option had been used. The file is closed on completion.
-format string
Return the checksum using an alternative format template.


The cksum package implements the checksum using a context variable to which additional data can be added at any time. This is expecially useful in an event based environment such as a Tk application or a web server package. Data to be checksummed may be handled incrementally during a fileevent handler in discrete chunks. This can improve the interactive nature of a GUI application and can help to avoid excessive memory consumption.
Begins a new cksum context. Returns a token ID that must be used for the remaining functions. An optional seed may be specified if required.
::crc::CksumUpdate token data
Add data to the checksum identified by token. Calling CksumUpdate $token "abcd" is equivalent to calling CksumUpdate $token "ab" followed by CksumUpdate $token "cb". See EXAMPLES.
::crc::CksumFinal token
Returns the checksum value and releases any resources held by this token. Once this command completes the token will be invalid. The result is a 32 bit integer value.


% crc::cksum "Hello, World!"

% crc::cksum -format 0x%X "Hello, World!"

% crc::cksum -file cksum.tcl

% set tok [crc::CksumInit]
% crc::CksumUpdate $tok "Hello, "
% crc::CksumUpdate $tok "World!"
% crc::CksumFinal $tok


Pat Thoyts


This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category crc of the Tcllib SF Trackers []. Please also report any ideas for enhancements you may have for either package and/or documentation.


checksum, cksum, crc, crc32, cyclic redundancy check, data integrity, security


Hashes, checksums, and encryption


Copyright (c) 2002, Pat Thoyts


crc32(n), sum(n)